Conservation in the Context of Tropical Forest Management

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DEVELOPMENT AND SOCIALLYSUSTAINABLE TOWARDENVIRONMENTALLY

B.IODIVERSITY

SERIES

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IMPACT

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Biodiversity Conservation in the Context of Tropical Forest Management Francis E. Putz

Kent H. Redford Public Disclosure Authorized

21653

John G. Robinson Robert Fimbel' Geoffrey M. Blate

September 2000

TheWorld Bank

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THE WORLDBANKENVIRONMENT DEPARTMENT

Biodiversity Conservation in the Context of Tropical Forest Management Francis E. Putz Kent H. Redford John G. Robinson Robert Fimbel Geoffrey M. Blate

September 2000

Papers in this series are not formal publications of the World Bank. They are circulated to encourage thought and discussion. The use and citation of this paper should take this into account. The views expressed are those of the authors and should not be attributed to the World Bank. Copies are available from the Environment Department, The World Bank, Room MC-5-126.

The International Bank for Reconstruction and Development/THE WORLD BANK 1818 H Street, N.W. Washington, D.C. 20433, U.S.A. Manufactured in the United States of America First printing September 2000

About the authors: Francis E. Putz ([email protected]) is Professor of Botany at the University of Florida; Kent H. Redford ([email protected]) is Director of Biodiversity Analysis and Coordination at WCS; John G. Robinson ([email protected]) is Senior Vice President and Director for International Conservation at WCS; Robert Fimbel ([email protected]) is Chief Scientist for the Washington State Parks and Recreation Commission; and Geoffrey M. Blate ([email protected]) is a Ph.D. candidate at the University of Florida. Substantial background material for this paper was provided by D. Nepstad, M. Guariguata, R. Noss, and C. Peters. We also acknowledge the contributions of E. Bennett, J. Ewel, P. Frumhoff, E. Losos, K. MacKinnnon, A. Moad, G. Platais, A. Plumptre, and R. Plumptre. This document does not represent an endorsement of any particular World Bank policy by the Wildlife Conservation Society.

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The Wildlife Conservation Society (WCS) is dedicated to being the most effective conservation organization, protecting and promoting a world rich in wildlife and wilderness. WCS manages more than 300 field projects in 53 countries and develops award-winning education programs for schools in the U.S. and abroad.

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At its celebrated wildlife parks in New York-the Bronx Zoo, the New York Aquarium, and Central Park, Queens and Prospect Park Wildlife Centers-WCS inspires over 4.5 million annual visitors to care about wildlife and wild lands and to participate in their conservation. To leam more about WCS, visit www.wcs.org.

Biodiversity Series

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Studies

These "Impact Studies" are a subset of the Biodiversity Series of the World Bank's Environment Department Papers. Within this subset the broader question of what the positive and negative impacts of human activities on biodiversity is addressed. The following studies have been published in this series:

1. BiodiversityConservationin the Context of TropicalForestManagement 2. Hunting of Wildlifein TropicalForests-Implicationsfor Biodiversityand ForestPeoples

Contents PREFACE

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ExEcurlvESUMMARY VIl Chapter 1 Introduction

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Chapter 2 Disaggregating "Biodiversity" Chapter 3 Disaggregating "Logging"

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Logging intensities 7 Log yarding methods 9 Logging and other silvicultural treatments 11 Reducing the impacts of logging and other silvicultural treatments

Chapter 4 Impacts of Forest Management on Biodiversity

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Background 15 Landscape impacts (see Appendix I) 16 Ecosystem impacts (see Appendix II) 19 Community impacts (see Appendix III) 21 Species impacts (see Appendices V and VI) 22 Genetic impacts (see Appendix VII) 25

Chapter 5 Overview of Biodiversity Conservation in Relation to Logging and other Silvicultural Treatments 27 Synthesis 27 Troubling assumptions Conclusions 30

Chapter 6 Recommendations

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BiodiversityConservation in the Context of TropicalForestManagement

APPENDICES I Impacts of Logging (and other silviculture treatments where noted) of Biodiversity in Tropical Forests 35 II Impacts of Logging (and other silviculture treatments where noted) of Biodiversity in Tropical Forests 39 III Impacts of Logging (and other silviculture treatments where noted) nent of Biodiversity in Tropical Forests 43 IV Bird responses (density based on inter-site comparisons) to Logging Organized by Feeding Guild 51 V Impacts of Logging (and other silviculture treatments where noted) Biodiversity in Tropical Forests 53 VI Primate responses (by feeding guild) to Logging in Tropical Forests VII Impacts of Logging (and other silviculture treatments where noted) Biodiversity in Tropical Forests 61 GLOSSARY

on the Landscape Component on the Ecosystem Component on the Community Compoin Tropical Forests, on the Species Component of 57 on the Genetic Component of

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BIBLIOGRAPHY

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Boxes

1 2 3 4 5 6

Few tropical forests are logged or burned only once 9 Enrichment planting 12 Is reduced-impact logging (RIL) cheaper? 13 The critical role of production forests in maintaining biodiversity in the tropics 17 Hunting in logged tropical forests 23 Lesser-known species-Marketing challenges, silvicultural impediments, or desirable diversity? 24

Figures 1 Logging intensities (m 3 /ha) for tropical forests 8 2 Generalized ranges of direct biodiversity impacts of timber yarding methods used for tropical forest logging as a function of level of technological sophistication required 10 3 Some impacts of logging on biodiversity as a function of distribution of logging activities and logging intensity 18 4 Expected effects of a range of forest uses on the components of biodiversity 27 5 Generalized biodiversity impacts plotted against expected short-term financial returns to forest owners or concessionaires 28 6 Generalized biodiversity impacts resulting from different approaches to forest management for timber 29

Tables 1

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Components and attributes of tropical forest biodiversity that might be influenced by logging and other silvicultural activities 4

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Preface This paper was prepared as part of the World Bank's Overlay Program and as a contribution to the Bank's ongoing Forest Policy review. The Overlays Program, launched by the World Bank in partnership with bilateral donors and NGOs, seeks to internalize global externalities into national environmental planning and the Bank's sector work, operations, and its dialogue with governments and partners. It is an iterative process, combining conceptual studies, reviews of state-of-the-art techniques for measuring and mitigating local, national and global externalities, and testing these concepts and tools in country-level studies as a means of identifying good practices for country planners and Bank task managers. The results will help guide national actions to conserve biodiversity, reduce greenhouse gas emissions, and protect international waters.

One of the most important forest uses is logging or timber harvesting. Logging is the most lucrative forest use and can cause severe direct and indirect environmental impacts. This analysis evaluates the impacts of logging on biodiversity in tropical forests based on a thorough review of the literature and on the best expert opinion.

The Overlays add a new dimension to traditional sector economic planning by analyzing environmental impacts and opportunities to internalize global externalities. This analysis launches the "Impact Studies" which asks the broader question of what the positive and negative impacts of human activities are on biodiversity. An analytical framework is used which allows for the systematization of these impacts across sectors and areas of particular interest.

Forests will continue to be harvested and timber harvesting will continue to be an important component of sustainable forest management. This is a reality we cannot escape. Therefore, as this practice continues we need to assure ourselves that it is ecologically and environmentally sustainable. The World Bank has a responsibility to its clients to inform them of best practices and what the potential consequences of natural resources management decisions are. This paper helps fulfill this responsibility.

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The study was commissioned from the Wildlife Conservation Society (WCS).A draft paper was prepared by WCS and the University of Florida and was distributed to an expert review panel. Supported by the Forest Policy Implementation Review and Strategy Process, these reviewers convened in Washington with the authors and Bank staff in late February, 1999for a productive two day workshop after which the paper was revised.

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Executive Summary Existing parks and protected areas are cornerstones of biodiversity conservation but on their own are inadequate to assure the continued existence of a vast proportion of tropical forest biodiversity. As a result, priority must be given to ensuring that the greatest possible amount of biodiversity is conserved outside protected areas by altering harvest patterns in these landscapes of resource extraction. Of all forest uses within tropical forest regions, logging or timber harvesting, is the most important to influence because not only is it the most lucrative, it also causes the most severe direct and indirect environmental impacts. Evaluating the impacts of logging on biodiversity in tropical forests is not as simple a task as many would believe. It depends on a thorough review of the literature and on the best expert opinion due to the complexities hidden under the seemingly simple rubrics "logging" and "biodiversity." As a first step in effectively analyzing the relationship between biodiversity and logging, it is essential to begin by disaggregating the terms "logging" and "biodiversity."

"biodiversity" into components (landscapes, ecosystems, communities, species/populations, and genes) and attributes (structure, composition, and function). It then disaggregates "logging" by detailing the vast range of activities subsumed under this term including variation of logging intensities, Biodiversity Series- ImpactStudies

logging methods, collateral damage, and silvicultural approaches. Using the richness present in both these terms, a framework for considering the impacts of logging and other forest management activities on the various components and attributes of biodiversity is presented. This framework is, in turn, used to evaluate the extensive literature covering different studies of logging in tropical forests. findings: 1.

2.

3.

4.

5.

6.

All consumptive uses affect some component or attribute of biodiversity, commonly affecting not only the target resource but other elements as well. As a result, only fully protected areas will conserve all components and attributes of biodiversity. Recognizing that all significant interventions in natural forests have biodiversity impacts, all silvicultural decisions necessarily represent compromises. Management for some goods or services necessarily involves management against others. Different intensities and spatial patterns of timber harvesting, along with other silvicultural treatments, result in different effects on the different components of biodiversity. Some components and attributes of biodiversity are more sensitive than others to forest management activities. There are some forested areas and some areas within forests, which should never be logged. vii

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7. Biodiversity objectives can and should be established within production forests. 8. In many cases the logging itself is not the major cause of biodiversity loss, but rather the indirect effects, often promoted by the presence of roads, (for example, hunting, forest fires, and the likelihood of deforestation) represent the major environmental threats. Unfortunately, due to the complexities hidden under the seemingly simple rubrics "logging" and "biodiversity", the answer to the question "Is logging compatible with biodiversity protection?" can only be the very unsatisfying "It depends." The paper does not conclude with uncritical support for sustainable forest management of timber as a conservation strategy. Such an endorsement is unwarranted given widespread illegal logging in the tropics, widespread frontier logging and logging of

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areas of high priority for biodiversity protection, the persistence of poor logging practices despite substantial efforts in research and training, and the generally slow rate at which most loggers are transforming themselves from timber exploiters into forest managers. Nevertheless, even harshly treated forests maintain more biodiversity than oil palm plantations, cattle pastures, or cornfields. From a biodiversity maintenance perspective, natural forest management is preferable to virtually all land-use practices other than complete protection. Forests that are carefully managed for timber will not replace protected areas as storehouses of biodiversity, but they can be an integral component of a conservation strategy that encompasses a larger portion of the landscape than is likely to be set aside for strict protection.

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Introduction

Existing parks and protected areas are essential for biodiversity conservation but inadequate on their own to assure the continued existence of the majority of natural landscapes, ecosystems, communities, species and genotypes in tropical forests. Even if the.oft-quoted goal of 10-12 percent protection were attained and the reserved areas were appropriately located and properly managed, up to 50 percent of tropical species would be expected to go extinct during the next few decades (Soule and Sanjayan 1998). Similar but often less well documented losses of the other components of biodiversity are expected. Another way of considering this dire prediction is that if biodiversity outside of protected areas is neglected, thousands of species are likely to disappear. Faced with this bleak future, the first priority should be to increase the area of forests under strict protection while at the same time improving reserve management. Mechanisms should be developed to halt road building and commercial logging in forest wilderness areas as well as in centers of diversity and endemism. However, promoting more biodiversity-sensitive management of forests outside protected areas is of almost equal priority, given the conservation potential of these still vast areas. Biodiversity conservation within forests managed primarily for timber production, for example, should be fostered by a combination of not logging ecologically important areas and by employing biodiversity-sensitive management methods within production areas.

within managed forests should be protected, and which approaches to silviculture to follow within forests used for timber production should be made on the basis of a wide range of considerations. Forests differ in their biodiversity value, in their capacity to support different intensities of silvicultural use, in pressures for conversion to non-forest use, and in the abilities of the relevant institutions to regulate their management. General conceptual approaches to zoning forests for different uses have been presented recently by various authors including Noble and Dirzo (1997), and Frumhoff and Losos (1998). Methods for integrating conservation functions at different geographical scales were reviewed recently by Poiani and others (2000). This paper focuses on the forests zoned for timber production. The goals are:

Decisions about which large forest areas should be designated for strict protection, which areas

In the search for land-use practices compatible with biodiversity maintenance, many

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To contribute to the development of a heuristic construct for considering the range of impacts of forestry activities on tropical forest biodiversity at.the levels of landscapes, ecosystems, communities, species, and genes. 2. To indicate the topics on which further research will be particularly useful in evaluating the impacts of different forestry activities on the various components and attributes of biodiversity. 3. To suggest ways to mitigate the deleterious impacts of forestry activities on tropical forestbiodiversity.

BiodiversityConservation in the Context of TropicalForest Management

environmentalists have focused upon logging [see Grieser Johns (1997) and Haworth (1999) for comprehensive reviews of the environmental impacts of logging in tropical forests]. This emphasis is not surprising given that of all forest uses, logging is often the most financially lucrative and has the most severe environmental impacts. The indirect effects of logging, particularly increased hunting (for example, Robinson and others 1999) and the increased likelihood of deforestation due to improved access, reviewed by Kaimowitz and Angelsen (1998), have also been highlighted recently. What has emerged from the dust, mud, chainsaw noise, and diesel fumes is the idea that conservation of some components of biodiversity could be facilitated by collaboration between loggers and environmentalists. Some of the latter oppose the idea of promoting better forest management as a means for achieving overall conservation goals (or at least oppose financial investment in such efforts, Rice and others 1997, Bawa and Seidler 1998, Bowles and others 1998). This opposition notwithstanding, consideration of the inevitability of logging in much of the tropics, the many constraints on expansion of nature reserves in tropical countries, the challenges of protecting and managing the parks already demarcated on paper, sovereignty issues, development needs, and the implicit adoption of the "use it or lose it" assumption,

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motivate other conservationists to continue holding sustainable forest management (SFM) as a worthy conservation goal in forests outside of protected areas (for example, Dickinson and others 1996, Chazdon 1998, Poore and others 1999, and Whitmore 1999). To help elucidate some of the factors upon which the compatibility of tropical forest logging and biodiversity protection depend, this paper first attempts to disaggregate the terms "logging" and "biodiversity." The wide range of logging intensities, logging methods, collateral damage, and silvicultural approaches appropriate for tropical forests is discussed. A framework for considering the impacts of logging and other forest management activities on the various components (=landscapes, ecosystems, communities, species/populations, and genes) and attributes (=structure, composition, and function) of biodiversity is presented. In the main section of the paper, the components and attributes of biodiversity are used to review the impacts of logging and other silvicultural activities on tropical forests. To promote readability of the text, much of the bibliographical review is presented in appendices organized by the components and attributes of biodiversity. The paper concludes by suggesting ways to enhance the compatibility of forest management for timber and biodiversity maintenance in tropical forests.

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Disaggregating "Biodiversity"

Biodiversity refers to the natural variety and variability among living organisms, the ecological complexes in which they naturally occur, and the ways in which they interact with each other and with the physical environment. This definition and the elucidation below is based upon OTA (1987),Noss (1990) and Redford and Richter (1999).Climate, geology and physiography all exert considerable influence on broad spatial patterns of biotic variety; local ecosystems and their biological components are further modified by environmental variation (such as local climatic and streamflow fluctuations) and ecological interactions. This natural variety and variability is distinguished from biotic patterns or conditions formed under the influence of human-mediated species introductions and substantially human-altered environmental processes and selection regimes (Bailey 1996, Noss and Cooperrider 1994).

the physical organization or pattern of the elements. Compositionrefers to the identity and variety of elements in each of the biodiversity components. Functionrefers to ecological and evolutionary processes acting among the elements.

In discussions of diversity there is always the lurking danger of assuming that "more is better." Were this the case, plowing roads through mature forests, clearcutting patches, and introducing alien species would all be reasonable. Although decisions about which species or community-types are most valuable are not straightforward, rarity is one obvious dimension that needs to be considered.

interactions between members of a biological community and their abiotic environment. Structureof this component might be measured through vegetative biomass and soil structural properties. Ecosystem compositionrefers to features such as biogeochemical standing stocks. Ecosystemjiunction pertains to processes including biogeochemical and hydrological cycling.

Biologicaldiversity can be measured in terms of different components (landscape, ecosystem, community, population/species, and genetic), each of which has structural, compositional, and functional attributes (Table1). Structure refers to

Diversity of the community componentrefers to the guilds, functional groups, and patch types occurring in the same area and strongly interacting through trophic and spatial biotic relationships. Structure of this component

BiodiversitySeries - ImpactSthdies

Diversity of the landscapecomponentrefers to regional mosaics of land uses, land forms, and ecosystem types. Structure of this component could be described on the basis of the areas of different habitat patches, through the perimeterarea relations of these habitat patches, or on the basis of interpatch linkages. Landscape compositionpertains to the identity, distribution, and proportions of different habitat types. Landscapefunction refers to issues such as patch persistence and interpatch flows of energy, species, and other resources. Diversity of the ecosystemcomponentrefers to

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Table I Components and attributes of tropical forest biodiversity that might be influenced by logging and other silvicultural activities Components Landscape

Organizedbythe componentsandattributesof biodiversity Struaure Composition Function Sizeand spatialdistribution of Identity, distribution, and Habitat patch persistenceand habitat patches(e.g.,seral proportion of habitattypes turnover rates; energyflow rates; stagediversity and area); and multi-habitat landscape disturbanceprocesses(e.g., extent, physiognomy;perimeter-area types; collectivepatterns of frequency,andintensity of fires); relations; patchjuxtaposition speciesdistributions humanlanduse trends; erosion and connectivity;fragmentation rates;geomorphicand hydrologic processes

Ecosystem

Soil(substrate)characteristics; Biogeochemicalstocks; vegetationbiomass,basalarea lifeform proportions andvertical complexity,density anddistribution of snagsand fallen logs

Biogeochemicaland hydrological cycling;energyflux; productivity; flows of speciesbetween patches; local climate impacts

Community

Foliagedensityand layering; canopyopennessandgap proportions; trophic andfood web structures

Relativeabundanceof speciesand guilds;richness and diversity indices; proportions of endemic, exotic, threatened,and endangeredspecies; proportions of specialistsvs. generalists

Patchdynamicsand other successional processes; colonizationandextinction rates; pollination,herbivory, parasitism, seeddispersalandpredation rates; phenology

Speciesl Population

Sexand age/sizeratios; range anddispersion;infraspecific morphologicalvariation

Speciesabundance distributions, biomass,or density;frequency; importance or cover value

Demographicprocesses(e.g., survivorship,fertility, recruitment, anddispersal);growth rates; phenology

6enetic

Effectivepopulationsize; Allelic diversity; presenceof Geneflow; inbreedingdepression; heterozygosity;polymorphisms; rare alleles;frequencyof rates of outbreeding,genetic drift generationoverlap;heritability deleteriousalletes and mutation;selection intensity; dysgenicselection

Note:Modified from Noss (1990)and Redford and Richter (1999).

includes consideration of vegetative physiognomy and trophic structure. Community composition refers to relative abundances of species and guilds. Community functions include flows between patch types, disturbance regimes (such as fires and floods), successional processes, and species interactions. Diversity of the species/population component refers to the variety of living species and their component populations at the local, regional, or global scale. Structure of this component might 4

be measured through population age structure or species abundance distributions. Species/ population composition pertains to which particular species are present. Function of this component refers to demographic processes such as recruitment and death. Diversity of the genetic component refers to the variability within a species, as measured by the variation in genes within a particular species, subspecies, or population. Structure of this component can be expressed on the basis of Environment Department Papers

Disaggregating"Biodiversity"

heterozygosity or genetic distances between populations in different patches (that is, metapopulation genetic structure). Genetic compositionrefers to which alleles are present

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and in what proportions. Genetic functions can be expressed on the basis of gene flow, genetic drift, or loss of allelic diversity in small, isolated populations.

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3

Disaggregating "Logging"

When properly planned and conducted, logging (=timber harvesting) is an integral component of forest management systems designed to promote sustained timber yields (STY), or the more all-encompassing goal of sustainable forest management (SFM). Unfortunately, logging in tropical forests all-too-often represents a timber "mining" activity carried out without regard for the renewability of this natural resource (for example, Putz and others 2000). Other silvicultural treatments designed to promote sustainability are often prescribed but are rarely applied. Due mostly to the desire to obtain voluntary third-party certification of good management from the Forest Stewardship Council (FSC), the transition from forest mining to forest management has finally started to occur in some areas in the tropics (Nittler and Nash 1999). Despite this progress, even within certified forests there are questions about how to most effectively and efficiently minimize the deleterious environmental impacts of logging and other silvicultural activities. This paper addresses many of these questions by reviewing the state of knowledge about biodiversity maintenance in exploited and managed tropical forests. It is critical to recognize that forest interventions of all types, from harvesting of fruits for home consumption to clearcutting for timber, all have impacts on forests that need to be understood and often deserve mitigation (Peters 1996). Nevertheless, logging is often the most damaging and generally the most financially lucrative of such forest interventions (Pearce and others 1999). Unfortunately, discussions Biodiversity

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about the compatibility of logging with biodiversity conservation are complicated because logging is carried out over a huge range of intensities, using a variety of techniques which may be applied carefully or in ways that result in a great deal of avoidable damage. The following sections focus on the issues of harvesting intensities, yarding methods (=how timber is extracted from the stump to haul roads), and ways of reducing logging damage. A brief overview of other silvicultural treatments used in timber stand management is also provided. Logging intensities Trying to conclude anything about the Try ity oflogging aboutethe compatibility of logging and biodiversity maintenance is made complicated by the wide range of logging intensities, yarding methods, and accompanying forest management practices to which tropical forests are subjected. The simple observation that logging intensities span more than two orders of magnitude (100 m 3 /ha) illustrates the challenge of generalizing (Figure 1). Even within the same forest management unit, logging intensities vary greatly at different spatial scales. At a small scale (1-10 ha), the typical aggregated distributions of tropical trees (Hubbell 1979) leads to locally severe logging impacts unless harvesting controls are implemented (that is, "tree-marking rules" are followed, Uhl and Vieira 1989, Crome and others 1992, Cannon and others 1994). The localized but severe direct impacts of roads, log 7


landings, and skid trails hardly need to be emphasized (Guariguata and Dupuy 1997). At a slightly larger scale (10-100 ha), stands vary in stocking of commercial species and in their accessibility due to terrain or edaphic factors. Where logging is carried out in areas designated for each year of management (=annual coupes), logging impacts tend to be aggregated at larger scales. Logging intensities also vary over time, tending to increase with local timber shortages, improved access, and greater willingness of markets to accept lesser-known species (Plumptre 1996). For example, in a remote part of the Bolivian Amazon loggers may harvest an average of only 0.3 m 3 /ha of 1-3 species (Gullison and Hardner 1993) whereas in similarly stocked stands in the more accessible

eastern portions of Amazonian Brazil, it is likely that 30-50 m3 of 20-30 species would be harvested Uohns and others 1996). The substantial number of studies conducted on the impacts of logging in tropical forests all concluded that soil impacts and damage to the residual forest all increase with increasing logging intensity (Ewel and Conde 1976, Sist and others 1998a). Proportions of both soil and residual trees damaged by logging range from 5 to 50 percent, depending on harvesting intensity, yarding method, and the care with which the operations are carried out. Interpretation of data pertaining to the relationship between logging intensity and residual stand damage is complicated by concomitant change in residual stand density; at the extreme, there is no residual stand in

Figure I Loggingintensities (m3/ha) for tropical forests. In most of these studies, as in most logging areas in the tropics, felling was with chainsaws and yarding with bulldozers or articulated skidders with rubber tires.

50 m 3/ha

< I rn/ha Bolivia

Venezuela (Kammesheidt1998)

(Gullisonand Hardner 1993)

00 m 3 /ha

150 m 3/ha

Indonesia

Malaysia

(Bertaultand Sist 1997)

(Pinardand Putz 1996)

Suriname

Costa Rica

Philippines

(Hendrison 1990)

(Webb 1998)

(Nicholson 1979)

Venezuela (Mason 1996) Australia (Cromeet al. 1992) Brazil

Malaysia

Oohns et al. 1996)

(Pinard and Putz 1996)

Australia (Crome et al. 1997) Uganda (Chapman and Chapman 1997)

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Environment Departnent Papers


clearcuts. Further complicating assumptions about logging damage is the fact that few tropical forests are logged (or burned) only once (Box 1).

Log yarding methods In this paper, particular attention is paid to the yarding phase of the timber harvesting process because much of the direct damage to tropical forest caused by logging occurs while logs are being extracted from the stump to roads or riversides from which they are then hauled or towed out of the forest. Yarding methods utilized in tropical forests range in technological sophistication, the collateral damages with which they are associated, and in yarding costs (Conway 1982). Accurate cost figures for yarding are difficult to obtain and problematic to calculate (for example, should impacts on future timber yields be included, and, if so, at what discount rate?). For the same volume of timber yarded, the range in biodiversity impacts

at the landscape, ecosystem, community, population/species, and genetic levels varies greatly along the continuum of technological sophistication of yarding methods that stretches from manual extraction to the use of helicopters (Figure 2). Note that Figure 2 hides a great deal of relevant variation. In particular, attempts to include another dimension expressing yarding costs (per cubic meter yarded to the roadside) have so far failed due to the multitude of factors that need to be considered, including labor costs, technical capacity, and discount rates, along with the values assigned to future harvest yields, non-timber forest products, biodiversity protection, and ecosystem services. Yarding can be carried out in an environmentally/silviculturally sensitive manner, or can be extremely destructive. The rankings of environmental impacts on Figure 2 are just suggestions of the typical amounts of damage associated with different yarding techniques. Box 1

Few tropical forests are logged or burned only once Logging and wildfires in tropical forests are causally linked (Holdsworth and Uhl 1997) and also share the characteristic of being self-promoting processes. Although the environmental damage resulting from unplanned logging of primary forest by untrained crews is justifiably receiving attention from researchers and policymakers, few logged stands are allowed to recover for the full cutting cycle or rotation stipulated in their management plans. Instead, forests are repeatedly entered by loggers who sequentially 'high-grade" the best remaining timber. Although the costs of road building are substantial, the first cut is generally the most lucrative. As more timber species enter commercial markets, and mills begin to accept smaller and lower quality logs, incentives for multiple entry logging increase. The same logging firms are sometimes involved in a series of entries into the same forest, but more often firms with lower operating costs and smaller equipment take advantage of the increased access provided during the first harvest. A familiar adage in Amazonia is "mahogany builds the roads." Reliable data on frequencies of multiple entry logging, either legal due to waivers issued by governmental agencies or illegal, are apparently rare, but the process is unquestionably commonplace. As with multiple entry logging, wildfires seldom occur only once (Peres 1999, Cochrane and Schulze 1999). In forests that are not naturally maintained by fire, the first fire opens the canopy and thereby subjects the understory to rapid drying. Fuel mass in the understory is augmented by trees killed by the first fire, and by grasses and other plants that regenerate under conditions of reduced competition. The resulting fire frequencies far exceed the historical rates. In the eastern Amazon, for example, fire frequencies in Paragominas have recently doubled and now occur far too frequently to allow forest recovery. Human made savannas and grasslands along with severely degraded forests due to frequent fires are becoming more the rule than the exception throughout much of the wet and moist tropics. On the basis of either the area affected or the magnitude of impacts, the direct damages attributable to tropical forestry are minor compared to those of wildfires.

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Figure 2 Generalized ranges of direct biodiversity impacts of timber yarding methods used for tropical forest logging as a function of level of technological sophistication required (assumes equal volumes of timber yarded). For mechanized ground-based yarding operations, conventional (non-RIL)and reduced-impact logging(RIL)impacts are contrasted.

Severe

Modest Low

(;reat Technological Sophistication

For ground-based yarding, using the smallest yarding equipment possible contributes to reducing the deleterious impacts of logging, W.Ahich yarding equipment is used is important, but so is the care with which yarding operations are carried out, as indicated by the contrasts between conventional and reduced-impact logging (RIL) on Figure 2. Unfortunately, although the silvicultural, environmental, and economic benefits of planning of log extraction routes have been recognized for many decades (see Putz and others 2000 for a review), well planned logging operations are still the exception in tropical forests. Most destructive yarding in tropical forests is carried out with bulldozers (=crawler tractors). Bulldozers are excellent devices for constructing roads but are unfortunately versatile enough to yard timber as well. The excessive damage to soils and residual trees during conventional 10

bulldozer yarding, especially at high intensities on steep slopes logged during wet weather by untrained crews is well known, but bulldozers still yard much of the timber in commercial logging areas in the tropics. With the loss of forest in accessible areas in much of the tropics, logging is increasingly being relegated to flooded, steep, rocky, or otherwise adverse terrain. Because ground based yarding from such sites can be prohibitively expensive, they have often been left as unlogged refugia within harvested areas. Their status as refuges is jeopardized by helicopter yarding, because helicopters can yard timber from even the most adverse sites. Obtaining timber from these sites is becoming more cost effective under some conditions. Although areas from which timber is harvested by helicopters are not dissected by skid trails, haul roads are still needed, and with them, all Environment

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Disaggregating"Logging"

the problems associated with increased access. An equally important concern about helicopter yarding is that areas traditionally avoided by loggers are rendered accessible and are likely to be harvested. Because helicopters leave no obvious trails, it is going to be very challenging to monitor their harvesting impacts.

Logging and other silvicultural treatments

regeneration, the second cut releases the established seedlings and saplings. There are innumerable variations on the themes of monocyclic and polycyclic harvesting, and each is appropriate under different conditions and in forests for which there are different silvicultural goals (Lamprecht 1989). Even within the same forest, the silviculturally most appropriate harvesting regime sometimes can change over

Logging can be either a cause of a great deal of avoidable damage or one of a series of silvicultural treatments designed to promote the regeneration and growth of commercial timber species while protecting ecosystem services and biodiversity. In logging areas where sustained yield of timber is a priority, various silvicultural treatments can be used in combination with the appropriate logging regime to promote the regeneration or growth of commercial species. Carrying out silvicultural treatments in conjunction with logging reduces their cost while simultaneously reinforcing the idea that logging itself can be silviculturally useful.

distances of less than 100 m (Pinard and others 1999).

Silviculturally appropriate harvesting prescriptions (from a timber stand management perspective) run the full gamut from single tree selection to clearcutting (Smith and others 1997). For forests with ample stocks of trees of all sizes of the commercial species (that is, negative exponential size-class frequency distributions), "polycyclic" (=uneven aged) methods such as single tree and group selection methods are generally suitable. In such a forest, the next crop is derived from the mixture of trees of intermediate size (for example, 20-40 cm dbh) at the time of first cutting. In contrast, at the time of the initial harvest the trees in the next crop in "monocyclic" (=even-aged) systems are seeds, seedlings, or saplings. Clearcutting is the most obvious example of a monocyclic system, but in "shelterwood management" a single-aged stand develops after two stages of harvesting. The first shelterwood harvest opens the canopy and otherwise stimulates

creating silviculturally unsatisfactory conditions such as where commercial species are favored by small canopy gaps or vines proliferate in large ones.

Biodiversity Series -Impact Stutdies

The most common method attempted for controlling timber harvesting in tropical forests is to simply set a minimum stem diameter for felling. Although theoretically easy to implement and monitor, minimum diameter rules are often inimical to achieving silvicultural goals. The problem with this system is obvious where minimum diameter limits are set below the sizes at which trees start to reproduce (Appanah and Manof 1991, Plumptre 1995). Minimum diameter rules also do not prevent harvesting of clusters of trees and thereby

Logging is often the most severe of silvicultural interventions, but there are other prescriptions designed to increase the stocking of commercial tree species, or to increase the growth of trees already present. Retaining seed trees in harvested stands is one possible way to increase stocking, but for species that require mineral soil seed beds or minimal competition for germination, establishment, and subsequent growth, seed tree retention needs to be combined with various other treatments. Seed beds can be modified and competition can be reduced by controlled burning, mechanical scarification, or herbiciding plants competing with seedlings of the crop species. Where natural regeneration fails, or where particularly 11


high stocking levels are desired, many foresters have tried planting seedlings of commercial species in gaps or along lines cleared through the forest (see Box 2). For stands in which regeneration of the commercial species is already established, various thinning and weed control treatments are often prescribed to accelerate tree growth and otherwise for "stand improvement." Thinning around potential crop trees, often referred to by tropical foresters as "liberation thinning," and vine cutting are two commonly prescribed but less commonly applied silvicultural treatments. In experimental areas where liberation treatments have been applied to enhance volume increments of commercial species, treatments are often prescribed at 10-year or more frequent intervals (de Graaf and others 1999). As in the case of logging, all of these other silvicultural treatments have impacts on biodiversity, but they have been much less well studied.

Reducing the impacts of logging and other silvicultural treatments Substantial attention has been given recently to Suced-ial loggin has Box 3ie Most o "reduced-impact logging" (RIL, Box 3). Most of the practices in the various RIL guidelines that have been promulgated of late have long been recognized as being environmentally sound and silviculturally appropriate (Bryant 1914). Full application of RIL techniques would represent a major step towards sustainable forest management (SFM), but RIL alone does not guarantee sustainability. Especially where tree species being harvested only regenerate in large clearings, the required silvicultural interventions to assure sustained yield of the same species may often be substantial (for example, mimicking the impacts of slash-andburn agriculture or hurricanes followed by fires, Snook (1996), Fredericksen (1998), Dickinson and Whigham (1999), Pinard and others (1999),

Box 2 Enrichment planting Despite scarcity of successes and millions of dollars wasted, enrichment planting in gaps or along cleared lines continues to be invoked as a way of restoring the commercial timber production potential of severely degraded forests. The principal problem with enrichment planting is failure to tend the out-planted seedlings (Dawkins 1961,Dawkins & Philip 1998).Admittedly there are cases where few silvicultural options remain. Unfortunately, enrichment planting is often utilized in forests that should not need such an expensive intervention. Furthermore, it is often not recognized that enrichment planting as often applied results in conversion of natural forests into plantations. Mason and Thiollay (in press) compared the impacts of enrichment planting with conventional selective logging in Venezuela and found the former to have greater negative impacts on birds. With these caveats issued, a description of a large-scale enrichment planting project in Sabah, Malaysia may be useful because the project implementers are avoiding some of the pitfalls of this technique and are trying to mitigate some of its deleterious environmental impacts. Funds from the FACE (Forests Absorbing Carbon Dioxide Emissions) Foundation of The Netherlands, Rakyat Berjaya (a subsidiary of the Innoprise Foundation) have been used to plant nursery grown seedlings of commercial species in several thousand hectares of forests degraded by extremely intensive and poorly controlled

logging in Sabah, Malaysia. The project has developed rapidly since its inception in 1992. Contract planters are now trained in dendrology so that they can recognize natural regeneration, and are paid for its retention at the same rate as for planted seedlings. Planters are also responsible for tending operations and are not paid for seedlings that do not survive 3 years. Site matching of species has also improved, as have nursery techniques for tending wildlings (=seedlings extracted from the forest) and raising large numbers of seedlings at relatively low cost. Finally, to promote retention of wildlife in the planting area, seedlings of fleshy- fruited trees are planted along with the mostly wind dispersed timber species in the Dipterocarpaceae. When the planted stands are ready to harvest in 50 or so years, the concessionaire hopes to harvest 50-100 trees per hectare, an intensity tantamount to clearcutting but perhaps preferable to the forest conversion to pulpwood plantation

option that has been adopted in much of the region.

12



Is reduced-impact

Box3 logging (RIL) cheaper?

Many people believe that RIL has been proven cheaper than conventional logging (CL) and are therefore perplexed at the lack of its adoption by loggers. Adoption of RIL techniques is of particular importance in the tropics where few countries have regulations that are both explicit enough and well enough enforced to prevent exploitative harvesting. Numerous studies over the past decades have shown that by planning skid trails and directional felling to facilitate yarding, logging damage can be substantially reduced (Bryant 1914, Nicholson 1958, Redhead 1960, Fox 1968, Nicholson 1979, Ewel and Conde 1980, Hendrison 1990, Johns and others 1996, Pinard and Putz 1996, Blate 1997, Elias 1997, Winkler 1997, Uhl and others 1997, Haworth 1999). Several experimental plot-based studies have demonstrated that due primarily to reduced yarding costs, such straightforward improvements in logging methods also translate into direct financial benefits to the loggers (Marn and Jonkers 1981, de Graaf 1986, Malvas 1987, Jonkers 1987, Hendrison 1990, Gerwing and others 1996, Bertault and Sist 1997, Barreto and others 1998, Holmes and others 1999, Boltz 1999). If RIL is cheaper than CL per cubic meter yarded to the roadside, then why haven't loggers spontaneously adopted RIL techniques out of enlightened self interest? A partial answer to this question may be that under normal operating conditions, at industrial scales, and especially on adverse terrain in wet forests, RIL may not always be cheaper (Putz and others 2000, Hammond and others 2000). Data on the comparative costs of RIL and CL from the "Reduced-Impact Logging as a Carbon Offset Project" in Sabah, Malaysia may serve to elucidate this issue. Tay (1999) and Healey and others (in press) reported that the financial profits from logging were substantially lower in a 450 hectare area harvested according to RIL guidelines than in a comparable area subjected to CL. The principal reason for lower profitability of RIL was the reduction in yield caused by reductions in the proportion of the area logged due to restrictions on bulldozer access to steep slopes. Despite regulations against timber yarding from steep slopes in Sabah, the practice is commonplace and loggers consider the timber foregone when RIL guidelines are followed as lost profits and thus do not spontaneously adopt RIL out of enlightened self interest. These findings indicate that the issue of cost effectiveness of RIL under adverse conditions deserves scrutiny and that loggers not using RIL techniques may not be acting in a financially irrational manner. In contrast to the apparent situation regarding RIL adoption in Southeast Asia, large vertically integrated forestry companies in Brazil have begun to invest heavily in RIL apparently out of enlightened self-interest. Although there is an additional incentive for adoption of more environmentally friendly logging in the form of better enforcement of regulations governing forest management operations, it appears that some companies have been convinced by the work of Baretto and others (1998), Holmes and others (1999), and others that their I

profits will increase if they adopt more efficient (and resource friendly) practices. Loggers in the region are also applying RIL techniques in response to an increase in demand for timber certified by the Forest Stewardship Council. Given the differences in the results of comparative studies on the financial profitability of different logging techniques, adoption of RIL techniques under some conditions may require either subsidies (such as carbon offset funds) or stricter regulations with better enforcement. The conditions under which incentives for RIL adoption are needed, and the best form and magnitude of these incentives are yet to be determined.

Fredericksen and Mostacedo (2000). This silvicultural challenge notwithstanding, careful planning and implementation of harvesting guidelines would represent a big step towards sustainable forest management. For all yarding methods, logging damage can be substantially reduced, and logging costs BiodiversitySeries -Impact Studies

reduced as well, by proper design, construction, and maintenance of road networks. Much of the cost of harvesting timber and a large proportion of the hydrological damage (for example, stream sedimentation) due to logging is associated with roads (Bruijnzeel 1992). For ground-based yarding, efficient skid trail layouts are also essential for reducing logging 13


damage and increasing yarding efficiency, but improper road siting often restricts skid trails to inappropriate places. Although the required density of roads is lower where aerial extraction techniques are used (such as skyline and helicopter yarding), roads are still needed and their locations can greatly influence logging costs and environmental damage. Guidelines for road construction are abundantly available and are well outlined in the FAO Model Code of Forest Harvesting Practices (Dykstra and Heinrich 1996). Unfortunately, forest engineering standards in most tropical logging areas are extremely low and there are too few experienced forest engineers involved in most tropical logging operations. It is important to note that because soil damage due to poor skid trail design or improper use, for example, reduces productivity, increases surface erosion, and has various other deleterious

14

environmental impacts, adhering to RIL guidelines has advantages regardless of whether the forest is allowed to regenerate or is replaced by an oil palm plantation or a maize field (Congdon and Herbohn 1993, Nussbaum and others 1995, Pinard and others 1996). The impacts of other silvicultural treatments on biodiversity (such as thinning and vine-cutting) depend on the intensity with which they are applied and on the proper designation of areas deemed inappropriate for stand "improvement." For example, vinecutting can enhance tree growth but undoubtedly has negative impacts on a wide variety of animals (Putz and others in press). Both biodiversity impacts and labor costs of vine cutting depend on whether only selected future crop trees are liberated or vine cutting is carried out as a blanket prescription.


Imnpactsof Forest Management on Biodiversity Background Human activities are highly variable in their

exploitation (Coomes 1995, Homma 1992). This ahistorical and wishful thinking is extremely angerocau a llowsits adhrentlt

influence on the components and attributes of

dneosbcuei

will always entail significant, often unknown, and almost always unappreciated consequences for one or more biodiversity components, primarily by redirecting matter and energy flows. The cumulative redirection is enormous

As societal concerns about the fates of tropical forests increase and human demands on forests

losisahrnst

binfleer onytheompone ant thattribults of believe that there exist easy, cost-free solutions biodiversity. Any human activity that results intmxliaino h lnt substantial resource extraction or modification t e

at the planetary scale as three examples illustrate: 1) Vitousek and others (1997) calculated that 40 percent of the Earth's terrestrial primnary productivity is being appropriated by humans, 2) 25 to 35 percent of the primary productivity of continental shelf marine ecosystems is consumed by humans (Roberts 1997), and 3) Postel and others (1996) report that humans now appropriate 26 percent of total evapotranspiration and use 54 percent of all runoff in rivers, lakes, and other accessible sources of water. Despite these statistics on current human impacts and the observations of the long-term impacts of previous generations of our species (Denevan 1992), many in the conservation and sustainable development community still maintain it is possible to both use and preserve biodiversity (Huston 1993) with no costs to either side. This claim is made regardless of a history of human over-exploitation of resources that began in prehistory (Goudie 1990) and is manifested most recently in the negative effects of tropical logging (Bawa and Seidler 1998, Frumhoff 1995) and non-timber forest product BiodiversitySeries - ImpactStudies

change, so should the ways in which they are silviculturally treated. For example, a few decades back when the primary component of sustainability of interest to most forest decisionmakers was sustained timber yields (STY), it was often recommended that logging be followed by silvicultural stand "improvement" treatments such as poison girdling of noncommercial trees, for a historical review see Dawkins and Philip (1998). Unfortunately, few of the tens of thousands of hectares of tropical forests that were treated according to the various silvicultural systems used in the 1950s (for example, the Malayan Uniform System and the Tropical Shelterwood System) remain, most having already been logged again, converted to oil palm plantations, or otherwise lost. Fortunately, there is now evidence from a lowland dipterocarp forest in Malaysia that at least the Malayan Uniform System (MUS) could achieve its silvicultural goals (Lee and others 1998) with mixed impacts on biodiversity, depending on the taxon in question. The forest treated by MUS and then studied 45 years later was, as intended, enriched in commercial timber trees, but also maintained much of the fauna and flora of primary forest. More studies of this sort are needed, and they need to be 15


better circulated so that more people will realize that at least "qualified" successes in tropical silviculture are attainable. In the following sections (4.2-4.6) the impacts of logging and other silvicultural treatments on the components and attributes of biodiversity using

hydrologic processes. The most severe impacts described in this section, however, result from indirect consequences of logging such as increased access to remote areas, fragmentation, and altered fire regimes.

Structure: The size and spatial distribution of

the framework elaborated in section 2.0 (see Table 1) are outlined; details are provided in the appendices. Summarizing the impacts of forestry activities on biodiversity in tropical forests is an effort fraught with problems in large part due to their immense diversity. Even at the species level, the diversity is difficult to imagine and each of the literally millions of species in tropical forests responds to different logging impacts in distinct ways. While some general response patterns are obvious, and others have emerged from field research, the idiosyncrasies and apparent inconsistencies of species responses need to be recognized. For example, chimpanzee (Pan troglodytes) populations have been reported to increase (Howard 1991, Hashimoto 1995), decrease (White 1992), and not respond to logging

tropical forest patches and the juxtaposition and connectivity of different forest patches across the necape are most patche across the landscape are most affected byite indirect impacts of logging. One of these impactsincreased access to humans-is often deleterious. Partcularly when logging roads penetrate far into the forest frontier in countries where there are numerous potential forest colonists, logging is almost invariably accompanied by increased hunting pressure (Robinson and others 1999, Robinson and Bennett 2000) and is often followed by deforestation as lands are cleared for agriculture (Kaimowitz and Angelsen 1998).

(Plumptre

contiguous

and Reynolds

1994, see Appendix

VI). In contrast, studies of terrestrial and barkgleaning insectivorous birds have consistently reported negative impacts of logging (see Appendix IV). Many more examples of this sort are discussed briefly below, and both cosset aredisconsistent pattefly below,erge. consistent and inconsistent patterns emerge.

Another indirect impact of logging on this attribute is fragmentation of previously or otherwise

connected

forest

patches. The resulting forest fragments, however, are typicaly not completely isolated for all species for all time. For example, wide lor roads may time. Forossable logging roads may represent uncrossable barriers for some forest interior species but roadsides with secondary vegetation attract

Landscape impacts (see Appendix I)

many large ungulates where they are more easily hunted (Robinson and Bennett (2000) in Logging affects the landscape component ofSaak,Mlyi)Whtelogdsnsar Malaysia). Whether loggred stands are biodiersit cangig lan by form andSarawak, y chaging lnd fors andinterspersed biodivrsity within s ecies-rich forest or in a ecosystem types across large geographic areas p p (Box 4). Logging shifts the regional mosaic of low diversity landscape dominated, for land uses. Although the landscape component example, by pulpwood plantations, also of biodiversity is the least sensitive to logging, influences long-term species maintenance. changes in the size, spatial distribution, and Furthermore, even small unlogged patches connectivity of habitat patches across the within harvest areas can serve as source landscape occur especially as the intensity of populations for some species after logging. The management interventions increases. These degree of fragmentation depends on whether changes in the habitat mosaic alter species logging is dispersed over large areas, or is distribution patterns, forest turnover rates, and concentrated in small areas (Figure 3). Where 16


Impacts of Forest Management on Biodiversity

Box4 The critical role of production forests in maintaining biodiversity in the tropics Tropical rainforests harbor approximately 50 percent of all terrestrial biodiversity and much of that biodiversity occurs in the lowland forests which are most accessible for, and thereby most threatened by, logging and agricultural conversion. In Peninsular Malaysia, for example more than 50 percent of all mammal species occur below 350 m and a startling 80 percent occur below 650 m (Stevens 1968, MacKinnon and others 1996). Worldwide tropical forest loss is estimated as at least 17 million hectares/yr, an area the size of Cambodia (FAO 1993). Dramatic as it is, this global total is probably a gross underestimate given that recent figures show that Indonesia alone has lost 18 million hectares of tropical forests between 1985 and 1997 in just three of the major Outer Islands-Kalimantan, Sumatra and Sulawesi. Most of this forest loss has occurred in lowland forest and logging has played a major role in that destruction. In many areas forests have been cleared and converted for agriculture, plantations and transmigration. However, it is not logging activities per se that have caused forest and biodiversity loss but poor concession management and new access along logging roads. These factors have allowed shifting farmers and hunters to colonize and clear logged areas. Moreover, areas that have been logged (whether legally or illegally) are more vulnerable to wild fires during El Nifio years; there is no doubt that poor logging practices contributed to the great Indonesian fires in 1998 when 5 million hectares of forest in Kalimantan burned, an ecological, economic and social disaster. It is not just the reduction in total area of natural habitat that concerns conservationists, it is also the fact that remaining habitat is being broken into ever smaller fragments within which species' populations are no longer viable. As habitats become more fragmented by clearance along new roads, protected areas will increasingly become "islands" and more and more species populations will be fated for local extinction. Fragmentation is particularly serious because few protected areas still cover a full range of altitudinal habitats as large areas of lowland forests, the most species-rich habitats and prime habitat for many large and wide-ranging mammals, have been excised from designated protected areas for logging (such as Kerinci, and Gunung Leuser National Parks in Sumatra). For Gunong Leuser National Park, for example, the main elephant, orangutan and tiger populations occur in the lower-lying production forests outside present park boundaries. Even more alarming is the recent increase in logging and other illegal activities within the boundaries of several National parks in Indonesia. The loss of bird species on Java is an indicator of what can be expected in Borneo and other large islands as forests are cut and fragmented. Studies of forest bird distribution shows that whereas in Borneo, Sumatra, and New Guinea, maximum avian species richness is still found in lowland forests and species numbers decrease with altitude, Java is atypical in having a depauperate avian fauna in the hill zone between 300 and 15OOrn. This pattern is interpreted as a result of long term deforestation since some predominantly lowland species have failed to survive in hill forests because they have been cut off from lower altitude populations which were a source of colonizers. Families of large birds such as malkohas have lost proportionally more species than families of small birds such as flowerpeckers. Moreover, Java has lost more species which are exclusive to lowland rainforests than species which can occupy secondary habitats, forest edge or open habitats. Small forest patches have lost more species than larger blocks, with extinction rates as high as 80 percent in 10-40 hectare plots compared to rates of 25 percent for areas over 10,000 hectares. These results have important implications for reserve design, forest management and biodiversity conservation. They emphasize thatforests must be maintained asforests and that reserves must be large, cover a wide altitudinal range and be connected by corridors of natural habitats. This necessitates a landscape approach to biodiversity conservation by managing production forests adjacent to core protected areas to maintain both permanent forest cover and biodiversity so that production forests become buffer zones that effectively extend and supplement the conservation estate (MacKinnon and others 1996, MacKinnon and Phillipps 1993).

preservation of forest interior biodiversity is the

conservation biologists (Noble and Dirzo 1997).

priority, concentrating

Fortunately,

generally

the pattern

Biodiversity Series

-

logging

in small areas is

recommended Impact Studies

by

concentration

due to associated of logging

cost savings,

activities

is one of the 17


Figure 3 Some impactsof loggingon biodiversityas a functionof distributionof loggingactivities(percent of area logged)and loggingintensity(m3/ha of timber harvested)

Concentrated Damage .t

.to

Moderate Yield LargeAreaImpact-Free

WorstCasefor Biodiversity Maximum Yield SmallAreaImpact-Free

Do Low Impact

C

J

?

MinimumYield LargeAreaImpact-Free Low

Dispersed Damage ModerateYield SmallAreaImpact-Free High

Area Logged (percentage)

steps towards improved forest management that loggers may find acceptable. The impacts of logging and other timber stand management activities on landscape structure are minimized when plantation products are used in place of those from natural forest. Opting for this so-called "New Zealand Solution" (Hunter 1998) is not currently an option likely to be exercised in many tropical countries. Nevertheless, as forests dwindle and economies grow (such as in Thailand, Malaysia, Chile, and South Africa), this solution will become more viable. Composition: Logging activities may directly and indirectly affect the identity, distribution, and proportion of habitat types in tropical forests. Forestry may directly affect composition of the landscape component of biodiversity by intentional creation of new types of habitats (such as forests converted into plantations). Furthermore, if silvicultural objectives are uniform across the landscape, inter-stand diversity is sacrificed by widespread application of the same stand "improvement" treatments. Perhaps most importantly, 18

improved access provided by logging roads indirectly fosters post-logging habitat changes by human forest colonizers, weeds, and wildfires. Setting aside reserves within logging areas may mitigate some of the deleterious impacts of logging and other silvicultural treatments. The specific location of reserves substantially influences their value in biodiversity conservation. Optimally, the full range of landscape features and habitats should be represented within protected areas. Function: Logging may markedly alter several landscape level ecological processes subsumed under the functional attribute of the landscape component of biodiversity. For example, logging roads, and activities associated with their construction, can greatly influence the permanence of the forest fragments they create by altering landscape level disturbance regimes. In large part, disturbance is altered because roads and skid trails provide ready access to the forest for both colonists and fire (see below). High intensity and widespread logging, especially if not carefully controlled, also Environment Department Papers

Impacts of ForestManagement on Biodiversity

influences hydrological processes at all levels perhaps including the regional climate. Where logging roads are wide and logging intensities are high, landscape level movements of animals can be disrupted (Goosem 1997), as can gene flow in plants when pollinators are restricted to isolated fragments by inhospitable surroundings. It should be noted, however, that the impacts of roads depends on where and how they are constructed, and change with time as the road and its margins mature (Lugo and Gucinski 2000). In this section the emphasis is on the impact of fires on the functional attributes of landscapes in full recognition of the importance of fires to all components and attributes of tropical forest biodiversity. Although fires have long played substantial roles in the ecology of tropical forests throughout the world (Goldammer 1990, Saldarriaga and West 1986), wildfires as exemplified by the recent Indonesian fires have recently increased in frequency, extent, and intensity in part due to widespread logging (Cochrane and Schulze 1999, Cochrane and others 1999). Canopy opening due to timber harvesting operations increases the rate of forest drying and thereby increases inflammability even in characteristically wet forests and swamps (Holdsworth and Uhl 1997). Perhaps equally importantly, vegetation proliferation along logging roads and skid trails greatly enhances fire penetration into forest interiors even where logging damage is slight or nonexistent. Whether or not the extensive forest fires that have recently become common can be indirectly attributed to logging, it is clear that fire damage often exceeds logging damage in many tropical countries. In Bolivia in 1999, for example, fires burned an estimated 20,000 km2 whereas logging was carried out in perhaps only one-tenth of that area (W. Cordero, pers. comm.). Although difficult to detect on satellite images, but see Souza and Barreto (in press) for recent Biodiversity Series- ImpactStudies

improvements in relevant remote-sensing methods, the impacts of the understory burns typical for tropical forest fires are substantial. Especially in forests that have not burned for many decades to centuries, the effects of even a single understory burn are great, even if they are not fully realized for many years. Typically small trees are killed whereas large trees often receive only minor basal damage. Unfortunately, basal damage exposes trees to wood rotting organisms; a high incidence of heart rot is typical of forests that burn at low intensities at infrequent intervals (F. E. Putz, pers. obs.). Elevated rates of tree mortality rates for many years post-fire are also characteristic in seldomburned forests. Such long-term data are difficult to obtain because accumulation of fuel in the form of fallen branches as well as post-fire proliferation of palms, grasses, and other firecarrying plants render forests very fire prone. Surprisingly, the effects of tropical forest fires on biodiversity have not been extensively studied (Leighton and Wirawan, 1986). Ecosystem impacts (see Appendix II) The deleterious ecosystem-level impacts of logging on tropical forests are widespread, substantial, enduring, and well studied (especially compared to the landscape and genetic components). The ecosystem component of biodiversity is somewhat more sensitive to logging impacts than the landscape component in part because management activities are usually implemented at this scale. In contrast to the landscape component, most ecosystem-level impacts are a direct consequence of logging activities. Logging purposely removes biomass from ecosystems, but it also alters their vertical complexity and soil characteristics. Depending on the silvicultural objectives, changes in structural heterogeneity may be intended. Whether intended or not, the structural impacts of logging alter the relative proportions of lifeforms and biogeochemical stocks, as well as nutrient and hydrologic cycling, productivity and energy flows. 19

BiodiversityConservation in the Context of TropicalForestManagement

Structure: Logging may affect the structural attribute of the ecosystem component of biodiversity by changing the biophysical properties of soils, spatial heterogeneity of forest stands, and biomass. The extent and types of ecosystem damage to these structural attributes depend on logging intensity, yarding system, and the care with which the operations are conducted. Soil compaction, for example, is a major problem during ground-based yarding operations especially where skid trails are unplanned and yarding continues during wet weather. Where compaction is severe, soil permeability and bulk density often require many decades to recover. Exposure of mineral soil after litter layers and root mats are bladed off by bulldozers is also a concern. Mineral soil disruption during bridge building, road construction and maintenance, and skidding operations also represent forest management activities that affect ecosystem structure and thereby have biodiversity impacts. Logging induced soil compaction negatively affects hydrology, which in turn alters the characteristics of watercourses. For example, water infiltration rates into soil, surface flow rates and volumes, and stream channel characteristics are all adversely affected by uncontrolled logging. Deposition of large volumes of unconsolidated sediments into streams during road construction and due to increased erosion from exposed mineral soils on log extraction routes can also greatly modify stream characteristics such as pool-riffle-run ratios. The impacts of such changes on aquatic organisms have been little studied in the tropics. Another impact of logging on ecosystem-level structure is reduction in biomass and alteration of necromass. Losses of biomass due to forest management activities include the amounts in the removed timber, damage to trees in the residual stand that result in mortality, and any silvicultural treatments that result in tree death. Biomass losses range from 5-10 Mg/ha at the 20

lowest logging intensities, to substantially greater amounts where heavy logging is followed by poison girdling of non-commercial trees in the residual stand. Necromass, including coarse woody debris, increases immediately after logging but may then decrease to levels below pre-logging conditions due to increased temperatures near the ground and associated increases in decomposition rates. Wildfires promoted by logging road construction and canopy opening, as well as controlled bums carried out for silvicultural purposes, can have obvious effects on biomass and necromass stocks in tropical forests. Maintenance of healthy communities, species populations, and gene pools is predicated upon protection of hydrological functions, nutrient cycles, and other ecosystem properties. Fortunately, methods for mitigating the ecosystem-level impacts of logging on tropical forests are well known. Switching from groundbased to skyline yarding techniques, for example, greatly reduces damage to residual stands, soils, and streams but allows harvest on steep slopes. The opposite trend in technological change also can have environmental benefits; log yarding with draft animals or by manual means generally results in substantially less logging damage than yarding with bulldozers (Cordero 1995). To enjoy these potential benefits, the expertise of experienced forest engineers should be more often called upon where logging does have to occur. Composition: One important way that logging affects the ecosystem-level compositional attribute of biodiversity is by changing biogeochemical stocks. For example, soil compaction reduces water holding capacity, which in turn leads to increased surface runoff. Limited storage capacity in natural streams is further reduced by sedimentation, which means that flow regimes can be greatly modified by logging, especially during the first years after logging is completed. Various RIL techniques, Environment Department Papers

Impacts of Forest Management on Biodiversity

such as installation of cross drains on skid trails, can greatly diminish these impacts. Where large volumes of timber are harvested and post-logging forest recovery is retarded by soil damage, fire, or weed infestations, standing stocks of nutrients in biomass are greatly reduced. Storage of nutrients released from biomass in necromass and soil organic matter is generally brief in lowland tropical forests due to accelerated rates of decomposition and low cation-exchange capacities in the soil. The

release. The deleterious impacts of logging on forest carbon balance can be greatly diminished by application of RIL techniques (Pinard and Putz 1996). Substantial biodiversity benefits are also likely to result from RIL, but this and other co-benefits have not been well studied. Other silvicultural treatments such as fire management, weed control, thinning, and enrichment planting have various impacts on both greenhouse gas emissions and biodiversity that should be investigated.

results can be substantial leaching and, if the forest is burned, volatilization of nitrogen and sulfur. Function: Logging affects the functional attribute of ecosystem-level biodiversity by adversely affecting hydrological and biogeochemical fluxes as well as productivity. Reduced plant productivity results in part from impeded root growth, a consequence of logginginduced soil compaction. Because most of the available nutrients are usually found near the top of the soil profile, blading of the soil surface also diminishes nutrient availability in local areas and otherwise interferes with nutrient cycling. In more extensive portions of logging areas where RIL guidelines are not followed, nutrient cycling and hydrological functions are greatly modified by reduced canopy

Logging, especially if followed by silvicultural treatments such as liberation of future crop trees from competition, can substantially change the physiognomy, composition, and trophic structure of forest stands. To a large extent, these modifications represent the goal of forest "refinement" treatments applied to increase volume increments and relative densities of commercial timber species. This "stand domestication" by nature reduces species richness; rare, threatened and endangered species may become locally extinct especially if they have no perceived commercial value. These changes in composition and structure affect numerous community-level ecological processes including colonization, predation and mortality rates, pollination, seed dispersal, and timing and abundance of flower and fruit

interception of rain and mist, decreased uptake

production.

of water and nutrients

Structure: The most obvious

by the diminished

logging-induced

biomass, and increased occurrence of surface erosion and landslides especially associated with improperly located and poorly constructed roads and skid trails.

impact on the structural attribute of community-level biodiversity is the change in proportions of successional stages in forest stands. Depending on harvesting intensities,

Changes in carbon storage and flux associated directly and indirectly with logging and other silvicultural activities influence whether forests are net sources or sinks of "greenhouse" gases. For example, substantial logging-induced transfers of living trees to coarse woody debris can have substantial effects on understory structure and dynamics leading to more carbon

planning of roads and skid trails, and training and supervision of workers, logging can result in large changes in the proportion of forest in mature, recovering, and early successional stages. In some severely disturbed areas, succession might be "arrested" by post-logging proliferation of vines, bamboo, and other nonarboreal growth forms. Silvicultural treatments such as thinning and vine-cutting can increase

Biodiversity Series

-

Impact Studies

21


the rate of succession and increase the proportion of stand growth concentrated in

microclimates that result from exploitation, silvicultural treatment, and by hunting (see Box 5).

commercial species, but not without affecting

Species impacts (see Appendices V and VI)

biodiversity in more than the intended ways. Composition: For the community component of biodiversity, logging affects composition by changing (often purposefully) the relative abundance of species and guilds inhabiting forest stands. Relative abundances of tree species with light demanding vs. shade tolerant regeneration, wind vs. animal dispersed seeds, vertebrate vs. invertebrate pollinated flowers, and thick vs. thin bark, for example, are all subject to change in logged and otherwise silviculturally treated forests. Likewise, sieviculturatiyntreatedfforest. uikewofanise, s rersntto odifrnguilsonml (such as understory insectivores and arboreal folivores) is influenced by forestry activities,. Depending on a great number of factors related to the intensities, spatial scales, and modes of forest intervention as well as characteristics of the focal taxa, effects of forestry activities can be negative, positive, or neutral. For example, in eight studies that considered the impacts of logging on frugivorous birds, two reported positive impacts at the guild level, three reported negative impacts, and three reported no change at all (Appendix IV). Function: The functional attribute of community-level biodiversity includes numerous key ecological processes (such as pollination, herbivory, seed dispersal and predation) all of which are affected by logging especially under the most intensive management interventions. Many of the effects on these processes are a direct consequence of altered resource abundance (for example fruit for frugivores or young leaves for folivores), which in turn result from the logging-induced changes in community structure and composition. In addition to being influenced by resource-base changes, these ecological processes are also affected by changes in forest 22

The species component of biodiversity has received the most attention from researchers concerned about the impacts of logging and other silvicultural treatments in tropical forests. The most obvious species-level impact of logging is on the abundance and age/size distribution of harvested and damaged trees. Depending on the intensity of logging and the care with which it is carried out, the reproduction, growth, and survival of a great number of species can be adversely affected. In reviewing this literature, it is important to note that the taxa studied were not selected at random. Instead, in many cases, the species chosenswer d, to becsensitie to,cand thus goo i da of fensitr impacs Structure: The most immediate and direct impacts of logging on the structural attribute of the species component of biodiversity are suffered by the harvested tree species. Their populations are often left greatly depleted, especially in the larger size classes of reproductive individuals when management is based solely on minimum diameter felling rules. Because of the spatial clustering characteristic of many commercial timber trees, the richest patches of forest are generally the most severely disturbed, unless logging guidelines specify minimum spacing between harvested trees. Changes in forest structure are suffered most by specialist species of the forest interior. After logging, many formerly shaded microenvironments in the forest interior become drier, brighter, warmer, and more easily exploited by some predators. For example, severe canopy opening adversely affects litter invertebrates and their predators. For species that are generalists in their diets and wide-ranging in their habitat use, such as many frugivorous canopy birds, the direct impacts of logging vary Environment Department Papers

Impacts of ForestManagement on Biodiversity

Box 5 Hunting in logged tropical forests The escalating scale of wildlife harvest in logged areas is an insidious problem that may undermine the biodiversity conservation potential of forests managed for wood production (Robinson and others 1999,Fimbel and others in press). Logging operations multiply the harvest of wildlife from tropical forests primarily by increasing access to previously remote areas. These same access roads serve as conduits for commercially traded meat and other wildlife products. Although the magnitude of the impacts of subsistence hunting of tropical forest animals (for food, feathers, and skins for example) by indigenous people are non-trivial (Robinson and Redford 1991, Redford 1992,Robinson and Bodmer 1999,Peres 2000),the impacts of commercial hunting are several orders of magnitude greater. Of particular concern is the tendency for hunters to target almost any species larger than 1 kg, including many species that are vulnerable to extinction due to their long life spans and low rates of population recovery (Bodmer and others 1997). Hunting pressures increases in logging areas partially because of the number of people involved in logging operations as well as by the increased access provided by logging roads. In formerly isolated forest areas, loggers themselves hunt (Ruiz and others in press) or provide ready markets for meat and other wildlife products (Wilkie and others 1992, Bennett and Gumal in press). Local communities quickly shift toward commercial hunting to supply markets to which logging roads provide access. This shift initiates a positive feedback cycle wherein money gained from wildlife products buys better weapons with which to hunt, which in tum increases the harvest. Such escalations are unsustainable, however, and some species become locally extinct. Loss of wildlife threatens the sustainability of tropical to the extent that the animals targeted by hunters play key roles in ecological processes including seed dispersal, seed predation, and herbivory (Redford 1992,Jansen and Zuidema in press). Even when animal species are not extirpated, their numbers may be reduced sufficiently such that they are rendered ecologically extinct. The loss of wildlife may have cascading effects on the structure and composition of the tropical tree community with deleterious consequences for recruitment of commercial timber species. Such dire predictions are most likely to be borne out in areas such as the Guyanas where a large proportion of canopy trees are dispersed by large animals (Hammond and others 1996).Finally, as human populations expand and forest landscapes become more fragmented, the potential for wildlife to recolonize defaunated areas will likely diminish. While the deleterious consequences for wildlife of logging and other silvicultural treatments (such as vine cutting) deserve further investigation and mitigation, it should be recognized that the indirect impacts of logging resulting from increased access often far outweigh the initial damage done by even the worst predatory logging.

from being somewhat negative, to neutral, to positive. For the understory species that are adversely affected by logging, the effects may persist for decades (Wong 1985, but see Lee and others 1998). It is worth reiterating that the imnpacts of hunting on populations of large and slow-reproducing animals generally overwhelm any potential benefits that they might have enjoyed after the canopy was opened by logging (Bennet and Dahaban 1995, see Box 5). Population sizes and structures of most species are also drastically modified by the fires that so often accompany uncontrolled logging. Biodiversity Series - Impact Studies

Species impacts of logging and stand refinement treatments are of particular concern in small forest management units. Private landowners with less than 100 hectares to manage, for example, may be unwilling to set aside 10 percent of their forest for species preservation. If their forests are surrounded by similarly managed or deforested areas, then blanket apation o refiement treatmet application of stand refinement treatments or heavy logging can take a heavy toll on commercial and non-commercial species alike. Composition: Logging affects the composition attribute of species-level biodiversity by 23


changing the abundance and distribution of species. Unless logging is accompanied by other silvicultural treatments designed to foster their reproduction and growth, the abundance and population structure of the harvested tree species are greatly modified by logging (see Box 6). Logging impacts on tree populations continue for many years after logging is completed because damaged trees suffer high mortality rates, proliferation of weeds (such as vines) interferes with tree reproduction and survival, and population size reduction and fragmentation can decrease pollination levels and change patterns and intensities of seed dispersal and predation. Species composition of animals also changes in response to the direct impacts of logging (such as canopy opening) and the associated indirect impacts as well (for example increased fire frequency and intensity, hunting, and forest conversion). Changes in species composition in response to forestry operations are by no means consistent

across or even within taxa. Our review of the literature on primates, for example, revealed few cases of consistent responses of species to logging (Appendix VI). This variation can be attributed to differences in logging intensities as well as to differences in the duration of postlogging population monitoring. Silvicultural treatments other than logging, especially vine cutting and crown liberation of future crop trees, might have more consistent deleterious impacts on canopy animals, but such impacts have been little studied. Small fragments of untouched forest that remain within even heavily logged forests serve as important refugia for plants and animals. Wildlife densities in these unlogged fragments can be very high during and shortly after harvesting, but then diminish as animals recolonize the surrounding matrix. Many 1munplanned" reserves are on steep or otherwise adverse sites, which certainly influences their function as refugia. Implementation of

Box 6 Lesser-known species-Marketing challenges, silvicultural impediments, or desirable diversity? Sustaining volumetric yields of timber is made challenging in tropical forests where many trees have little market value (Plumptre

1996). Particularly where just a few species of light-demanding

trees have ready

markets, species that are commercially lesser known or that have less desirable timber properties often render regeneration-enhancing treatments prohibitively expensive (Fredericksen 1998, Pinard and others 1999). Where markets for formerly lesser-known species have developed and they can therefore be harvested profitably, forest managers can financially justify creating the large canopy openings required for regeneration of the most valuable light-demanding timber species. The same lesser known species that interfere with timber stand management treatments and present challenges for wood technologists and marketing firms represent an important component of forest diversity. One indication of their importance is that whereas tree species with wind dispersed seeds (such as Dipterocarpaceae and Meliaceae) dominate the international timber trade (ITTO 1996), a high proportion of species producing less well known timbers produce fleshy fruit and animal dispersed seeds (Jansen and Zuidema in press). Silvicultural treatments applied to promote regeneration and growth of commercially desirable species might be made more feasible by increased market demand for what are currently lesser known timbers. While promoting sustained yield of the species being harvested, these silvicultural treatments intentionally result in at least locally substantial modification of pre-intervention stand structure and composition. Compromises between sustained yield and the more all-encompassing goal of sustainable forest management need to be informed by research on the direct and indirect impacts of increased timber harvesting (Fredericksen and others 1999).

24


Impactsof ForestManagementon Biodiversity

helicopter yarding, and to a lesser extent other aerial yarding techniques, may place many of these unlogged patches in jeopardy. Function: Demographic processes (such as survivorship, fertility, and recruitment) and growth rates are two key functional attributes of the species component of biodiversity that logging affects. Populations of many organisms are susceptible to large fluctuations after logging due to both the direct impacts on forest conditions (for example microclimate and fragmentation) and the indirect impacts fragmentingfioand forest condirectsim Te s of hunting, fire, and forest conversion. The proliferation of disturbance-adapted taxa in logged-over forests, some species of which are not native or were not previously common in the area, can have large but as yet little studied imnpactson the resident flora and fauna. Genetic impacts (see Appendix VII) The genetic component of biodiversity is likely to be the most sensitive of all components to logging because of reductions in effective population size and interruptions in gene flow. At present, however, little is known about the genetic structure of any tropical organisms, even commercially valuable timber trees (Ledig 1992). Furthermore, the techniques required for assessing the genetic structure of populations are sophisticated and expensive. Except in a few cases, concerns about dysgenic selection, genetic drift, and other genetic problems are based on controversial theory that is rapidly developing as evidence accumulates. Structure: Logging affects the structural attribute of the genetic component of biodiversity by reducing effective population sizes and heterozygosity. Effective population sizes of both commercial and non-commercial species are reduced by harvesting, other silvicultural treatments, forest fragmentation, weed proliferation, and wildfires. There are also good reasons to be concerned about the effects of logging and stand improvement treatments on dioecious species and in small forest Biodiversity Series -

Impact Studies

management units in which population sizes of all species are correspondingly small. Allelic frequencies of commercial species change after removal of a large proportion of healthy reproductive adults. For species with high densities of advanced regeneration, genetic structure of their populations are unlikely to change dramatically after selective harvesting, unless collateral damage is severe. Timber stand improvement treatments also may affect the genetic structure of species targeted for removal (such as woody vines) as wetr as their (uha od ie)aimpacts elahavehiapparently associates, but these not been studied. Given the high proportion of vines and other plants that resprout after cutting (=coppice), large impacts on genetic cure are lkely. structure are unlikely Composition: The fact that most species are rare in tropical forests implies that allelic diversity will decrease with increasingly intensive management interventions. Unregulated harvesting of all merchantable individuals of commercial species, for example, has immediate impacts on allelic frequencies that continue to change due to decreased effective population sizes. Deleterious recessive genes may become more apparent due to dysgenic selection and heterozygosity may decline due to the "bottyeneck" effect in the small, isolated potions that inut smarvested populations that result from harvesting, forest fragmentation, and other direct and indirect impacts of forestry activities (Styles and Khosla 1976,Murawski and others 1994aand b, but see Newton and others 1996).

Function:Logging may affect the functional attribute of the genetic component of biodiversity by interrupting gene flow, which in turn influences outbreeding rates. Decreased effective population sizes coupled with losses of pollinators and seed dispersal agents can result in reduced gene flow and inbreeding depression in populations of both commercial and noncommercial species. Especially vulnerable are populations represented by scattered mature 25


individuals and very few juveniles (for example many "long-lived pioneers" such as the mahoganies). Given the high proportion of tropical tree species that are dioecious or

26

obligate outcrossers, only very severe reductions in effective population size are likely to have much effect on gene flow (Ghazoul and others 1998).


Overview of Biodiversity Conservation in Relation to Logging and other Silvicultural Treatments

5 Synthesis

The impact of these silvicultural approaches on

A way of graphically displaying the impacts of logging on tropical for-ests (Figure 4) based upon the various components and attributes of biodiversity as described above was developed. Along the vertical axis of our framework the five components of biodiversity were arrayed in the order of increasing susceptibility to logging impacts (landscape, ecosystem, community, population/species, and genetic). The horizontal axis arrays a variety of approaches to silviculture in order of increasing intensity.

each biodiversity component using three categories were assessed. First, each biodiversity component was scored as 'mostly conserved" for cases in which their attributes are expected to usually stay within their natural range of variation. Second, biodiversity components were scored as "affected" for cases in which their attributes are expected to frequently fall outside their natural range of variation. Finally, biodiversity components were scored as "mostly lost" for cases in which their

Figure 4 Expectedeffects of a rangeof forest useson the componentsof biodiversity -

___-

Genetic fA 3} 5

0

c

Species

.Legend: NTFP= Non-timber forest prod-

_

~~~~~~~~~~~~~~~ucts

.

MQSTLYRIL

>

~~~~~MOSTILY

.1%

-oa

LOST

E

6 Community

AFFECTED

._%

>

.2

\csse

\

Ecosystem

MOSTLY \ n0

0

m

.position, .

\

L

A

~

x x~

Refinement = Silvicultural treatments such as liberation of future crop trees from competition, which can substantially change the physiognomy, comand trophic structure of forest stands which are applied to increase volume increments ' and relative densities of Enrichment planting = Increasing the stocking of commercial speciesby planting seedlings (or seeds) in logging gaps or along

Yx

clearedlines t~


Reserves = Protected areas within logged units

commercialtimberspecies

CONSERVED

Landscape

= Reduced-impact logging

-900 CL = Conventional logging

27


attributes are expected to almost always fall

use capability, biodiversity

outside their natural range of variation.

capabilities and desires of local stakeholders. At least two other dimensions of this multidimensional topic are captured in Figure 5, on which it is indicated that every forest activity can be carried out over a range of intensities. Correspondingly, each forest-use activity generates timber volumes and financial profits that also range widely (Figure 6). Recognizing that forest use practices vary over time with, for example, market fluctuations and political change, and that biodiversity impacts are a function of a multitude of interacting factors operating at different temporal and spatial scales, it is hoped that Figures 4-6 present an accurate "snapshot" of the relationship between biodiversity conservation and forest management.

The scoring process used for Figure 4 was admittedly subjective; the scores were based on a reading of the literature and the authors' experience. It is fully recognized that particular situations might warrant different scores, and it is emphasized that the purpose is to illustrate what is believed to be a useful analytical process rather than to obtain perfectly accurate scores. It is also emphasized that this framework serves to suggest hypotheses that seem to be important research topics for conservation biologists from a number of different disciplines. The responses summarized on Figure 4 actually represent a multitude of impacts from a diversity of silvicultural approaches applied with varying degrees of concern for biodiversity over a large range of scales. Additionally, Figure 4 addresses neither the issue of profitability of different forest uses nor issues related to land-

value, or the

The impacts summarized in Figure 4 and the ranks and ranges of impacts and profits on Figure 5 are based on a combination of literature reviews and the authors' subjective estimations. For example, under the range of stocking levels,

Figure5 Generalized biodiversity impactsplottedagainstexpectedshort-termfinancialreturnsto forest ownersor concessionaires (NTFPs= non-timberforest products) Severe et

(A

Y

v

E

'hi~~~~~~~~~~~~~~~i

.t

1g

nv/e tona oggin (CL)/

Reced u

/

E .0

Modest

P Small

28

areas

Financial Profitability

Great

EnvironmentDepartmentPapers

Overview of BiodiversityConservation in Relation to Loggingand other SilviculturalTreatments

Figure 6 Generalized biodiversityimpacts resultingfrom different approaches to forest management for timber. (CL= conventional logging,RIL= reduced-impact logging, refinement= anyof a varietyof silvicultural treatmentsappliedto increaseratesof timbervolumeincrement; and,reserves= protectedareaswithinloggedunits)

Severe

E

mn

4-.

sia 1 Modest 0

1

2

3

4

5

6

CommercialTimber Production(m3 /ha/yr) terrain, and accessibility that logging is carried out, reduced-impact and conventional logging overlap in both impacts and profitability. Nevertheless, particularly where logging is carried out on steep slopes or under otherwise adverse conditions, application of most RIL guidelines results in immediate profits that are lower than those enjoyed by unconstrained conventional loggers. This observation helps explain why where regulations are non-existent or unenforced, conventional logging will likely be used to log such areas. Correspondingly, some of the impacts of high intensity RIL overlap those of low intensity conventional logging, but the former generally has fewer adverse environmental impacts than the latter. Troubling

assumptions

Three widely held and interlocking assumptions about tropical forests complicate the issue of the compatibility of forest management for timber and biodiversity conservation: Biodiversity Series

-

Impact Stuidies

1) Tropical forests are often assumed to have developed their current structure, composition, and functional properties under a disturbance regime characterized by small, localized, and natural perturbations. The importance of unrecorded widespread cataclysmic anthropogenic and natural disturbances, especially those of past centuries, is seldom recognized. 2) It is often assumed that regenerating trees harvested for timber is simply a matter of protecting advanced regeneration (for example, seedlings, saplings, and poles) and providing small canopy openings in which they can mature.

3) Many people believe that devolution of authority over forests to indigenous groups and other rural communities will enhance efforts towards sustainable management 29


and biodiversity conservation (Luckert 1999, Putz 2000). While these assumptions hold true in some tropical forests, many of the trees currently being harvested actually regenerated under conditions very different than those of today or those that will be created by harvesting alone. The most familiar example is provided by the neotropical and African mahoganies (Meliaceae spp); these trees and many others like them are the heritage of slash-and-burn agriculture, hurricanes, river meanders and/or catastrophic fires of centuries past. The problem confronting silviculturalists managing for such lightdemanding species is that promoting regeneration requires intensive stand manipulations which are expensive and have great impacts on the biodiversity present immediately prior to intervention (Lugo 1999). Despite accumulating evidence of substantial and long-term pre-historical and more recent impacts of humans on what were formerly considered "natural" ecosystems, it is important to recognize that the current rates, spatial scales, and intensities of human-induced perturbations often far exceed the resilience of tropical forests. Forest recovery after disturbances such as mechanical clearing for pastures, for example, is known to be extremely slow, especially if the pastures are large or intensively used. Natural regeneration in such areas can be accelerated through application of silvicultural treatments, but full recovery of diversity, from the genetic to the landscape level, will require centuries, if it occurs at all. For example, although leaf biomass may recover quickly, in abandoned agricultural clearings coarse woody debris accumulates at rates measured in centuries. Research progress on methods for afforestation and reforestation should not beguile us into believing that, once destroyed, tropical forests can be recreated. The cause of social equity may be well served by devolution of management responsibility to local communities, but the biodiversity benefits 30

are less secure. Some communities, such as the municipalities in Bolivia that have recently received control over substantial forest areas, may be indifferent about conservation (Kaimowitz and others 1998). In other cases, such as some communities in Nepal, devolution of forest control has had substantial conservation benefits. Obviously the process of devolution deserves scrutiny lest some turn out to be worse forest stewards than the logging companies and national governmental agencies they replace. Empirical evidence suggests that community behavior towards forests depends on the forest richness or forest poorness of their particular situation, but many other factors are likely involved and deserve investigation. Conclusions All consumptive use affects some component or attribute of biodiversity, commonly affecting not only the target resource but other factors as well (Redford and Richter 1999). The population/ species component is most commonly understood to be affected by silvicultural activities although effects, some of which are subtle or cumulative, are undoubtedly often missed even in this comparatively well studied component. Of increasing importance is an understanding of how the community and ecosystem components have been (Runnels 1995) and are being affected by logging and other silvicultural activities (Noss and Cooperrider 1994, Vitousek and others 1997, Fimbel and others, in press). Recognizing that all significant interventions in natural forests have biodiversity impacts, all silvicultural decisions necessarily represent compromises. Management for some goods or services necessarily involves management against some others. What are "weeds" to timber stand managers are food sources, rare species, carbon stores, or inter-crown pathways for other human and non-human stakeholders. The biodiversity compromises involved in deciding whether to cut vines, retain seed trees, or enhance seedling establishment by carrying out controlled burns should be informed by Environment Department Papers

Overview of BiodiversityConservation in Relation to Logging and other Silvicultural Treatments

research. Unfortunately, very little is known about how tropical forests can be managed in the most biodiversity friendly manner. Researchers have instead focussed on enumerating the deleterious environmental impacts of uncontrolled logging by untrained and unsupervised crews. To inform decisions about tropical forest management and to assure that biodiversity is protected to the maximum extent, more research is needed on how to maintain diversity in forests selected for logging. The large and rapidly growing body of literature on ecosystem management in both north and south temperate forests (such as Kohm and Franklin 1997, Lindenmayer 1999) should provide inspiration and starting points for tropical researchers intent on solving biodiversity related problems associated with forest management. The primary conclusions to derive from these analyses are that:

a

*

D Different intensities and spatial patterns of timber harvesting, along with other silvicultural treatments, result in different effects on the different components of biodiversity. Some components and attributes of biodiversity are more sensitive than others to forest management activities. Only extremely limited use will protect all components (that is, large protected areas are essential for biodiversity conservation).

The capacity to mitigate the deleterious environmental impacts of logging and other silvicultural treatments should not be construed as constituting unilateral support for sustainable forest management as a conservation strategy. Such an endorsement is unwarranted given widespread illegal logging in the tropics, widespread frontier logging and logging of areas of high priority for biodiversity protection, the persistence of poor logging practices despite substantial efforts in research Biodiversity Series

-

Impact Studies

and training, and the general slow rate at which most loggers are transforming themselves from timber exploiters into forest managers. Nevertheless, even the most harshly treated forests maintain more biodiversity than tree farms for pulpwood, oil palm plantations, maize fields, or cattle pastures. Furthermore, logging is often the environmentally least damaging of land uses that are also financially viable (Pearce and others 1999). Given these conclusions, effective mechanisms for financing forest protection and environmentally sound forest management are needed. It might also prove useful to evaluate critically the limits to the assumption that well managed forests are less likely to be converted to other land uses than forests that are logged without apparent concern for sustainability. By focusing on the deleterious environmental impacts of tropical forest management activities, we often lose sight of the fact that from a biodiversity maintenance perspective, natural forest management (that is, maintaining forests as forests) is preferable to virtually all land-use practices other than complete protection. The number of taxa with reportedly inconsistent, neutral, or positive responses to logging is an indication that timber harvesting is not necessarily incompatible with protection of many components and attributes of biodiversity. This conclusion derives even greater support from the fact that nearly all of the studies conducted to date on the biodiversity impacts of logging were carried out after unplanned logging by crews with no training in reduced-impact logging techniques and no incentives to reduce their impacts. As forest management practices improve under market pressure or pressure from land-owners, the deleterious environmental impacts of logging and other silvicultural activities are likely to be substantially reduced. Forests that are carefully managed for timber will not replace protected areas as storehouses of biodiversity, but they can be an integral 31


component of a conservation strategy that encompasses a larger portion of the landscape than is likely to be set aside for strict protection. In other words, forests managed primarily for timber, if managed properly, will supplement

32

and effectively extend the conservation estate. Finally, it should be recognized that landscape management is consistent with the ecosystem approach emphasized by the Convention on Biological Diversity (CBD).


6

Recommendations

1.

Given that all substantial forest interventions affect some component or attribute of biodiversity, the best way to assure biodiversity conservation is through the establishment and protection of large, properly located, and well managed reserves and protected areas.

components of reduced-impact logging and various other pre- and post-logging silvicultural activities. Particular attention should be paid to plant and animal species with attributes that render them susceptible to logging-induced extirpation (Martini and others 1994, Pinard and others 1999).

2.

In some parts of the world and some types of forest, there should be no logging at all.

Regional guidelines for certification need to be developed and regularly updated to reflect increasing knowledge about

3.

Existing legislation and regulations should be enforced. Where they do not exist, or are weak they should be created or updated to reflect current conservation and sustainable resource management concerns.

7.

4.

Within forests used for logging and other silvicultural activities, biodiversity conservation is enhanced by setting aside a portion of the area for complete protection. Optimally, these reserves should be large, shaped so as to minimize edge effects, cover representative areas of all the ecosystem types present, and include features of special concern for biodiversity maintenance such as water courses, rock outcrops, and salt licks.

retention of nest and den trees as well as species of great importance to biodiversity conservation. 8. Wildfires need to be controlled. Successful lled. Sude e contro fir fire control programs will need to include public awareness building as well as implementation of existing technologies and methods. Research is needed for developing cost-effective fire control measures with minimal biodiversity impacts.

5.

Where logging is to be carried out, reducedimpact logging guidelines (Dykstra and Heinrich 1996) should be fully implemented by well trained crews.

9.

6.

Researchers need to determine the financial and environmental costs and benefits of the


biodiversity so as to assure that certification efforts realize their conservation potential. Measures to protect biodiversity should be included in all forest management plans. Particular attention should be paid to the

While continuing to promote and develop community-based wildlife management prograrns, hunting by loggers and market hunting of slow reproducing species should be prohibited. Enforcing existing laws will in many cases confer substantial protection to species threatened by over-hunting. 33


10. Training is needed for researchers who will develop biodiversity-sensitive silvicultural methods as well as cost-effective methods for monitoring the environmental impacts of silviculture. Training is also needed for the field crews that are responsible for implementing the recommended practices. Perhaps the most critical shortage is of forestry/conservation "research practitioners" who understand both the broad scientific and the more specific technical aspects of tropical forest management.

34

11. The biodiversity impacts of devolution, plantation conversion, certification, 12. forest-based carbon offsets, and global trends in timber markets need to be monitored. 13. Linkages to the policy arena must be pursued. Ecosystems provide important services which typically are not internalized into the decision making process. Legislation and their regulations are an integral part of this process and should be reviewed, updated and enforced.


Appendix I Impacts of Logging (and other silviculture treatments where noted) on the LandscapeComponent of Biodiversity in Tropical Forests

Biodiversity Series

-

Impact Studies

35

Impacts of logging (and other silviculture treatments where noted) on the landscape component of biodiversity in tropical forests

Category

Vegetation, Soil& Water

-

Structure Fragmentation / roads+ greateraccess to

>

humans 4 increased deforestation (Kaimowitz & Argelsen1998) >

Tree populations, biomass, andcommunity compositionaffectedmoreby edgeeffects than by patchsize(Amazonia: Gascon& Lovejoy1998)

LandscaPe attributes Composition 50%forestarealogged+ specieslost

(Eastern Amazon:Nepstadet al. 1992)

>

Increasedspatialheterogeneity of habitatsafter > 140yrs of agroforestry, logging, & charcoal productionfollowedby 50yrs regeneration (PuertoRico:Garcia-Montiel & Scatena1994) >

Ecological degradation of 1°forestfragments from increased edgeeffects& newhabitat matrix(Amazonia: Gascon& Lovejoy1998)

Maintenance & recoveryof species composition in loggedpatchesdependson landscape context(Liu& Ashton1999)

Patches(I - 100ha)of unlogged forestsin heavilyloggedarea(500-1000ha,80-120

areas(Sabah, Malaysia: Pinard& Putz1996) Primates Non-rodent mrommals >

Increased smallmammalrichness in forest fragmentsb/cof increased edgeandnew habitat matrix

Birds

firesdue to canopyopeningand roads (Amazonia:Cochrane& Schulze1999)or fuel accumulation fromfire protection(Miombo woodlands,Africa:Chidumayo1988) >

m3 /ha) on steepslopes(>350) and in rocky

Rodents & Marsupials

>

Increased humancolonizationandfire & decreasedmigrationof animalsandgeneflow in plants(if pollinatorsare restrictedto fragments) Morethan 50yrs requiredfor recoveryof preloggingstructure(Uganda: Plumptre1996) 200yrs necessary for recoveryof spp composi-tion followingloggingdamage (Malaysia, forestgapmodel:Kurpicket al. 1997)

Increase inmixedforest(w/ valuabletimber o Impoundments dueto undersizedor failed spp)& decrease of Cynometraforestpatches culverts& bridgeabutmentskill treesand may afterarboricidetreatmentfrom 1951-90 influencefauna(F.E.Putz,pers.obs.) (Uganda: Plumptre1996) )> Increased likelihoodof largescaleaccidental

;O Complexmosaicof foresttypes& disturbance w/ 85% swampforest& only 15%lowland forestescaping loggingdisturbance (W. Kalimantan, 8 yrs post-logging: Cannonet al. 1994) >

Function >

Gascon & Lovejoy1998)

Harvestgapswarmerthan naturaltreefallgaps (Amazonia: Vitt et al. 1998)

Herps

>

Insects

>

Soilorganisms

Neotropical frogs- see rodents above(Gascon & Lovejoy 1998) Lossof species& genesof butterfly communitiesb/c of conversion of 30% of landscapeto agricultureandforestry (Neotropics: Brown 1997)

Appendix II impacts of Logging (and other silviculture treatments where noted) on the Ecosystem Component of Biodiversity in Tropical Forests

Biodiversity Series

-

Impact Studies

39

Impacts of logging (and other silviculture treatments where noted) on the ecosystem component of biodiversity in tropical forests Category Vegetation, Soil& Water

Structure P Reduced biomass, basalarea,andstemdensity > (Uhl et al. 1991,Silvaet al. 1995,Pinard& Putz 1996,Webb1998,Finegan & Camacho1999)

Ecosystem Attributes Composition Function Thin barkedspeciesmostsusceptible to P Increased vulnerabilityto fire: ignitionafter2 logging(andfire) (Amazonia: Uhl & Kaufman weeksw/out rainin gapsvs.monthsin 1990;Pinard& Huffman1997) understory(Amazonia: Cochrane& Schulze

>

Reduction in largetreeswith hollows& holes importantfor wildlife(Australia: Gibbons& Lindenmayer 1996)

>

2/3 basalarea,3/4 numberundamaged trees, > Higherrichness (trees> 20cm dbh)in logged P Decreased evapotranspiration & infiltration; I/5 no of emergents (>30 m), & 1/3 vs.unlogged, butwhenequalnumbersof trees increased surfaceflow 4 nutrientlosses commercial volumeof unlogged forest sampledrichnesswasequal(W. Kalimantan, 8 (Brtower1996, Poels1987,Bruijnzeel 1992), but (Venezuela, 19yrs post-harvest of 10trees/ha: yrs post-logging: Cannonet al. 1998) nutrientbssesdon'trestrictproductivity (Proctor Kammesheidt 1998) > T related to 1992)

>

Forestsurfacefireskill40-95%of alltreesw/ dbh > 10cm(Amazon:Nepstadpersobs)

geography thanwhethera patchwaslogged; > richnesshigherin westof reserveandin logged patches(L.tanda, 60yrspost'sustainable logging': P 36% biomass lossfrom Increased treePkp-e16)yst motlt (Aaoi, IAA fro frgmn Plumptre 1996) mortality(Amazonia, I00 m from fragment ~&Knrzna edge,10-17yrspost-fragmentation: Laurance etal. 1997)

Soilbulkdensity 6 yrspost-logging 60%greater thaninundisturbed forest(Malaysia: Malmer& Grip1990); skidtrailsestimated to require> 50 co'rhdaiccduty(aly: yrsto recoverhydraulic corductvity 96(MaVsia: K& K 1996)

>

Increaseinorganicfuels(56to 180tons/ha)on > forestfloor (easternAmazon,post-logging: Uhl &Kaufman1990,Uhl& Vieira 1989)

Reduced densitiesof timberspp& shiftin dominance & agestructureof canopyspp (PuertoRico,post 140yrs agroforestry,

100-170M tonsof carbon/yremittedfrom 1981-1996 (Asia:Houghton& Hackler1999) 0.5%of totalglobalcarbonemissions (Brazilian

>

Soildisturbance mainfactorlimitingseedling regeneration & establishment (Kalimantan: Gardingen et al. 1998)

logging, charcoalproduction& St yrs regeneration: Garcia-Montiel & Scatena1994)

Amazon,1996-97:Nepstadet al. 1999)

>

5-40%of forestfloor disturbedby roads,skid > trails& tractortracks(Cannonet al. 1994 Johnset al. 1996,Pinard& Putz 1996,Sistet al. 1998a,Holmeset al. 1999)

Epiphytic& stranglerFicussppsufferhighrates > of damage (Malaysia, post-logging: Lambert 1991)

PostCL, streamsuspended solidsandturbidity were 12x& 9x > controland levelspersisted at least5 yrs; RILlevelswere 2x > controlbut recoveredafter2 yrs (Malaysia: Zulkifli& Anhar 1994)

1999,Nepstadet al. 1999)

> >

Vegetation, Soil& > Water Vegetation

Soilproperties(i.e.BD, total porosity,sathydr > conductivity, & resistance to penetration) required12-52yrs (skidtrailslongest)to & recover(Malaysia: Kamaruzaman Kamaruzaman 1996)

Woodyvinesincreased w/in 100m of edges > butdidn't compensate for lost biomass from increased tree mortalityAmazonia forest Laurance> fragments 10-17 yrspcstfragmentation: et al. 1997)

>

Limitingharvestgapsto < 650 m2 (< 2 trees/gap) enhanced dipterocarpregen& Gardingen inhibitedpioneerregen(Kalimantan: et al. 1998)

>

Watershedsedimentloadswere 18x higher5 mospost& 3.6xhigherI yr post-logging (Malaysia: Douglaset al. 1992) 200 yrs necessary for recoveryof sppcomp (Malaysia, forestgap followingloggingdamages model:Kurpicket al. 1997) Runoffas% precipitationrangedfrom58% 94% in plantationsconvertedfrom forest on method(Malaysia: Malmer1992) depending

>

mayincrease Road& skidtrail impoundments methaneemissions (F.E.Putz,pers.obs.)

>

Sedimentloadshavenegativeeffectson dwsra qai ie(utai:Cmbl downstreamaquaticlife (Australia:Campbell& Doeg1989)

Primates

>

Non-rodent mammals Rodents & Marsupials

>

Bats

>

Longdistanceseeddispersal andspecies movements to/from differenthabitatpatches likelyimpeded(nospecificdata) Species movements to/from differenthabitat patcheslikelyimpeded(no specificdata) Speciesmovements to/from differenthabitat patcheslikelyimpeded;seedpredationrates likelyaltered(nospecificdata) Speciesuseof differenthabitatpatches& pollination& seeddispersalrateslikelyaltered (nospecificdata) Speciesuseof differenthabitatpatcheslikely altered;dependingon spp.,pollination, rateslikelyaltered; predation,seeddispersal (nospecificdata)

Birds

Herps

>

Harvestgapsmuchlargerthannaturaltreefall gaps& thushavelesslitter andshade& more Vitt et al. 1998) intenselight(Amazonia:

>

Tree basalareaandcommercial volumes recoveredwithin40yrs postloggingw/ MUS (Malaysia: Manokaran 1998)

>

>

Birdsppdeclinew/ increasing disturbance (Lawtonet al. 1998)

>

Category Insects

Soilorganisms

CommunityAttributes Composition

Structure >

)

25%-75% reductionin soil mycorrhizae > (Malaysia,post-logging:Alexanderet al. 1992)

Arthropod diversity decreaseswhen structural > complexity decreases(Holloway et al. 1992; Gardner et al. 1995)and/or b/c of changesin understory,litter, & soil microclimate (Blau 1980,Kremen 1992,Spitzer et al. 1997, Camilo & Zou in press) Termite richnesslower in clear-cuts, but higherin regeneratingplots than I' forest (Cameroon),but overall richnesswas similar in 1°, 3 yr and 17yr secondarysites (Malaysia: Eggletonet al. 1995);changesin termite comp maybe delayedafter disturbance(Eggletonet al. 1997)

>

Nematodesdeclined alongdisturbance gradient & were 40% lower in clearcut vs. 1' forest (Bloemerset al. 1997)

>

Soilfungi increasedfrom 17 spp in 7-yr regrowth to 27 in 16-yr regrowth; soil microbial popin'spositivelycorrelated w/ tree density & basalarea(India:Arunachalamet al. 1997)

>

Ectomycorrhizaldiversity greater under open & regeneratingcanopiesthan in undisturbed forest (Kalimantan,9 months post clear-cut or partial logging,trees > 50 cm dbh: Inglebyet al. 1998)

>

Termite populationsincreaseafter conventionalloggingmore than after RIL (Sabah,Malaysia,80-120 m3/ha harvested:F.E. Putz, pers.obs.)

(MUS = MalayanUniform System,a monocyclic approachto timberstandmanagement)

Function Various ecosystemprocesseswill be relatively unaffected(Vitousek 1990)

Appendix III Impacts of Logging (and other silviculture treatments where noted) on the Community Component of Biodiversity in Tropical Forests

Biodiversity Series -

Impact Studies

43

Impactsof logging(and other silviculturetreatments where noted) on the community componentof biodiversityin tropical forests Category Vegetation

>

>

Structure proportion of open > Increased canopy(Uhl&Vieira1989, Thiollay1992, Cannon et al. 1994,Mason1996); upto 50%ingapsvs.5-10% D (Hartshor 1978, Denslow

Attributes Community Composition Increased speciesrichness(esp.light-demanding pioneertrees,shrubs i andlianas)> 10yrs post-logging (Brazil:Verissimoet al. 1995, Magnusson et al. 1999;Salicket al. 1995,Silvaet al. 1995,Delgadoet al. 1997,CostaRica:Webb 1998) > Aggressive shade-intolerant sppdominateandcompetitivelyexclude otherplants(Uganda: Struhsaker1997)

Function Decreasedseeddispersalof 6 timber speciesin logged+ huntedforestvs. logged+ protectedforest(CostaRica: Guariguata et al. in press) Fruit productionof treeslower IOyrs post-logging (Amazonia: Johns1992)

Greaterdensityof > Multipletree fellinggapsmostdiverse,butdominatedby pioneertree spp(CostaRica:Webb 1998) understoryvegetation5-6 yrs postharvest(Venezuela: Mason1996)

>

Highdegreeof outcrossing and low density of matureindividuals(neotropics: Murawski1995,Stacyet al. 1996)

Remaining largetrees o Highdominanceof few sppin heavilydisturbedhabitats(e.g.,roads) inadequate to sustainfuture (CostaRica:Guariguata & Dupuy1997)

>

Seedproductionlower inseveraltimber species(Uganda:Plumptre1995)

harvests(Philippines, I 5 yrs post-SLS: Tombec& Mendoza1998)

Large-scale, long-termshift insppcomposition afterlogging,augmented spp(Uganda: Plumptre by arboricidetreatmentof non-commercial 1996) >

Reduced tree density& > canopyclosure,denser cover < 2 m aboveground, & equalgroundcover (Indonesia, 5 yrs postselective:Hill et al. 1995)

Reduced leafbiomass but increased leafquality;

& compositioninloggedvs.logged+ No changein overallrichness thinned(Nicaragua; Salicket al. 1995) irradiance4 moreearlysuccessional spp(Swaine1996, Increased Mulkeyet al. 1996,Whitmore1998)especially vines& pioneers(Lowe & Walker 1977,Cannonet al. 1994) flli (Peters Post-logging is differentthano ostg

>

dominanceof fastgrowingtimberproducingtree spp.after Increased silviculturalrefinement(Malaysia, MUS:Chua1998)

>

Vinespp.richness anddensitiesrecoverto pre-MUSloggingand treatmentby 40 yrs (Malaysia: Gardette1998)

reduced log distribution,

Lich

d

ir

d mo

d

d

40

-

>

-

d

Increasedself-pollination attributedto low (Murawski densityof floweringindividuals & Hamrick 1991,1992)4 lessseed

seedsfallin higher Wind-dispersed numbersingapsthan in understory (Augspurger & Franson1988,Loiselleet al. 1996)4 highercolonizationlevelsfrom spp. seedfor wind-dispersed

Reduceddispersal of seedscarriedby large-bodied, gap-shyfrugivores(Gorchov et al. 1993,Forget & Sabatier 1997)or that

regenerating stems, and siMcultural treatirent(Maoas div MUS:Wolseley et al01998) overall trsieeutualteamnt(Mlysa,MSsWize e

arescatterhoarded by caviomorphrodents

(Madagascar, RIL,

Palmspp.richnesslowerinloggedandMUStreatedforestthanin 1°forest (Malaysia NurSupardi et al. 1998)

& Milleron 199I; Forget 1990,

Vegetation

>

Fewerlargediametervines40 yrspostMUSthanin II forest Gardette1998) (Malaysia:

>

Mortality rates 4x higher for spp w/ dbh > 40 cm (S. India, 10-I5 yrs postselective logging:Pelissieret al. 1998)

>

for Denningtreeslessavailable arborealrodents& marsupols afterselectiveloggng & Laurance (Auistralia: .A (autra Laurance1996;Invchoa & ) Sorianoin

>

Tree mortality increasedafter liberation/refinement treatments (Costa Rica:Finegan& Camacho 1999)

>

Vine cutting promotes tree growth &

>

Primates

>

reduces loggingdamagebut removes important intercrown pathwaysfor wildlife (reviewed in Putz 1991)

selectivelogging Repeated of large abundance reduces treesandshiftscomposition species to earliersuccessional (Australia:Home& Hickey 1991 > Increasedinfantmortality for variousspp. immediatelyafter logging, but some spp recovered 612yrs post logging > (Malaysia:Johns& Johns

eta]. 1996) >

Frugivore/folivoredensities (asabove)- 3 spp decreased,2 increased,4 spp showed no change;again,severalspp responded differently in different sites/studies(Uganda:Plumptre & Grieser Johnsin press)

susceptibilityto predators for non-volant arboreal animals(reviewed in Putz et al. 2000)

>

Lemursin dry forest (< 10% affectedby logging)- increasedsightingsof > all spp attributed to increasedfruit & higherfoliage quality on remaining trees (Madagascar:Ganzhorn 1995)

Predation of smallprimates by raptors may increasein responseto vine removal (Suriname:S. Boinski, pers comm.)

>

Monkeysin Zaire - 4 spp preferred secondaryforest: 3 others preferred primary forest (Zaire: Thomas 1991) Folivores- hunting hasgreater negativeimpact than logging(Africa: Oates et al. 1996)

>

CA1

Herbivory & frugivory - enhancedby low intensity (< 10% affected) logging disturbance (Madagascar:Ganzhorn 1995); data lackingfor higher intensities, but presumed asvariable as changesin spp densities Seeddispersal& predation - no specific data; probably varieswith animaldensities Vine cutting and liberation thinning increasedlocomotory costs and

1995)

vp~

> yrs post-logging, Omnivore densities(1-25 trees harvested/ha,I-SO Africa, Asia,Amazon)- 8 spp decreased,13spp increased,5 spp showed no change;severalspp showed opposite results in different studiesand/or different sites (reviewed in Plumptre & GrieserJohnsin press) Folivore/frugivoredensities (asabove)- 6 spp decreased,5 spp > increased,3 spp showed no change;as above,severalspp showed opposite responsesin different studies/sites(Plumptre & GrieserJohns in press);huntingaffects folivores more than loggingitself (Africa: Oates >

>

Primatedensitiesdecreasedin responseto logging& MUS (Malaysia: Laidlaw 1998)

Category Non-rodent mcmnmds

Community Attributes Composition

Structure >

Function

Browsers/grazers (e.g.,Asianelephant,Africanbuffalo,gaur,banteng,& > sambardeer)increase(if no hunting)b/c of increased food quality (Oateset al. 1990,Waterman& Kool 1994)& quantityJohns1992);the onlysensitivesppin thisguildwasthegiantforesthog(Hylochoerus meinertzhageni) (reviewedin Davieset al. inpress)

If no hunting,increased herbivory;if huntingdecreased herbivory

Carnivores - mixedresponses & few data;sppwith restricteddiets mostsensitive(reviewedin Davieset al. inpress) > Species favoredby hunters(e.g.,duikers,pigs,peccaries), for special trade(e.g.,elephants) androadsidefeeders(e.g.,Synceroscaffer,Bos spp)decline(Davieset al. inpress) >

Large,slow(moving& reproducing) speciesdecline(huntinga confounding factor)(Lahm1994,Grieserjohns 1997) > Species dependenton fruits/seeds of timberspecies(e.g.Susbarbatus, Caldecott1991)onclosedcanopy(e.g.,Muntiocus atherodes, Heydon 1994;Giaoet al. 1998),or with limiteddietaryflexibilitydueto energeticrequirements (e.g.,Tragulus spp.Heydon& Bulloh1997) decline. > Arboreal marsupials - I spdeclined & 4 sppunaffected after8-10trees(50-55> m3) harvested/ha (Australia: Laurance & Laurance 1996) > Smallmammalpopulations mostsensitive- according to models:(a) > Sciuridae, Echimyidae & othercanopydependentfrugivores/granivores; and(b) sppw/ low RAandrestrictedgeogrange(Ochoaet al. 1993, 1995;Utrera 1996;Ochoa1997;reviewinOchoa& Sorianoin press) >

Rodents and

Marsupials

'

Smallmammal populations leastsensitive - according to models: Didephidae & Muridae; semi-arboreal omnivores/predators increase (e.g.,Didelphis spp.& Philander opossum; seeaboverefs) > Rodentspprichnessincreased soonafterlogging(Uganda, 9 trees/ha, 62% canopyopen:lsabirye-Basuta & Kasenene 1987,Muganga1989), butdecreased by 16yrs post(Lwanga1994) > Rodentspp.richnessincreased, 2 dominantspp.decreased inabundance butincreased in bodymassafterlogging(China:Wu et al. 1996)

Increased seedpredationrates(espif hunting)(e.g.,Terborgh& Wright 1994) Decreased predationon largeseedsif large seedpredatorsextirpated(Putzet al. 1990) Increasein Muridaemayincrease colonizationof smallseededtree spp. (Hammond& Thomasin press)

Bats

>

>

>

>

> Birds

Birds

dispersalof pioneerplantspp; > Increased (e.g.,Carollia.Artibeus& Sturnira)increase Pioneerplantdispersers decreasedpredation 1986,Fleming1988,Fentonet al. 1992,Kikkawa& (Charles-Dominique Dwyer 1992,Brossetet al. 1996,Utrera1996,reviewin Soriano& Ochoain press) could in insectivorepopulations & vert predators)- decline(e.g.,Artibeus > Reductions (insectivores Phyllostominae with rates herbivory increased in result Tonatia elongatus, Phyllostomus bidens, Vampyressa obscurus, deleteriouseffectson forestresource sauropila)or disappear(e.g.,Vampyrumspectrum,Tonatiasylvicola, productivity(Soriano& Ochoain press) (Fenton Chrotopterusauritus,& Peropterixkoppleri,Emballonuridae) et al. 1992,Brossetet al. 1996,Utrera1996,reviewin Soriano& Ochoa in press) (5.8m3/ha,trees> afterlogging & kcalextinctions guildcomplexity Reduced Brosset Guiana: strips(French byenrichment 40cmdbh);effectsexacerbated inSoriano reviewed Ochoain press; inVenezuela: similarfindirngs et al. 1996; & Ochoainpress) fast-flyingsppw/ long,narrowwingsdo bestb/cof Open-forest, gaparea;dominated6-yr postsitew/ 6-7 trees/haharvested increased Crome& Richards1988) (Australia: afterbrushing Spppreferringmediumto denseunderstorydisappeared in foreststructure(Millerin press) to changes highsensitivity indicating

>

- nc or increasein most ) frugivore/insectivores Nectarivore& generalist spp(ohns 1989a,1992b;Lambert1991;Thiollay1992;Zakaria1994, 1996;Mason1996;reviewsin Mason& Thiollayin press,Zakaria& Francisin press,& Plumptrein press)

Herbivory& frugivory- reducedfor figeatingsppb/c of lower post-harvest densityof Ficusspp(Lambert1991)

>

> & otherspp (e.g.,Tyrannidae) Terrestrial& sallyinginsectivores on forestinterior (e.g.,thoseinmixed-sppflocks)decrease depending w/ logging(ohns 1989a,1991a, 1992a;Lambertet al. 1992;Thiollay 1995;Grieser 1992;Zakaria1994;Bennet& Dahaban1995;Fanshawe inMason& reviews 1998; Plumptre & Johns1996;Mason1996;Owiunji Thiollayin press,Zakaria& Francisin press,& Plumptrein press)

b/c of Predation- expectedto decrease (b/c of reducedinsectpreyabundance hotter/drierconditions)(Mason1995)

>

in > Seeddispersal- reducedb/c of avoidance responses & largefrugivores- inconsistent foliagegleaners Predators, of largeopeningsin forestcanopy(Stouffer a; Lambertet al. 1992;Thiollay1992; aohns1991 differentsites/studies & Bierregaard1995a,b) Grieserjohns1996;Zakaria& Nordin 1998;reviewsin Mason& Thiollayin press,Zakaria& Francisin press,& Plumptrein press) decreased; > Colonizationrates-expectedto increase insectivorous increased; Understoryspp.- nectarivorous whenrefugesprovidedw/in loggedareas Mason1996) (Venezuela: planting enrichment latter trendworsenedby -(ohns1996)

>

CommunityAttributes

_____________________________

Composition

Structure

Category

>

Interiorunderstorysppdeclinedby 37-98%;generalists & spp associated w/ densesecondgrowth,edges& largegapsincreased; overallrichness andabundance down27-34%(FrenchGuiana,1-17yrs post,38%undergrowth& 63% canopyloss:Thiollay1997);(other study:3 trees/ha,10yrs post)- lowerdiversityb/c of moreuniform habitat(Thiollay1992)

>

Flycatchers, wren-warblers, trogons& woodpeckersdeclined; nectarivores & somefrugivoresincreased (Malaysia, 8 yrs post-logging: Lambertet al. 1992)

9

Spp.richnesslowerthanunlogged(Indonesia: Marsden1998) 1/3sppexpectedto disappear(Liberia,loggedfragment:Kofron& Chapman1995)

>

Herps

_._____________

Function

in Competition& Predation- increases generalistspp(Vittet al. 1998)

>

densityof largelizards& alteredcomm > Heliothermiclizards- increased structure(Amazonian treefallgaps:Vitt et al. 1998)

>

No changein reptilecommunitycompor abundance (< 10%damage,2- > Colonization- generalistspp(e.g,Hyla geographica) increase(Caldwell1989) 12yrs post-logging: Bloxamet al. 1996)

>

Loweramphibian diversity(Amazonia, highintensityloggingor logging& & roads:Pearman1997,Vitt et al. 1998) fragmentation

>

afterhigh Sppthat livein leaflitter mostseverelyaffectedespecially intensitylogging(e.g.,monocyclicharvests); w/ lessintenseloggingmost of 2° forestby largepredatory spppersistin shortterm,but invasion lizardsmayextirpatesmallfrogs& lizards;somefrogsppincreaseafter loggingb/c of pondinginskidtrail rutsor in streamimpoundments (reviewedinVitt & Caldwellin press)

Insects

>

Heteroptera,Homoptera,> Communitycompof Araneae,Hymenoptera, differedin 1°forest,logged Coleoptera,Orthoptera& Lepidoptera Nummelin1996) (Uganda: forest& plantations Spp.restrictedto understory,leaflitter & soilmostvulnerable(reviewed in Ghazoul& Hill in press) Geometridmothdiversitylowestin abandoned clearcut,highestin > Intachatet al. 1997;Ghazoul& Hill in forestloggedw/ MUS(Malaysia:

>

Press) mothdiversityafterlogging+ conversionto Lowerlepidopteran dung& carrionbeetleslessaffected(Malaysia: plantation;Coleopteran Hollowayet al. 1992;Ghazoul& Hill in press)

>

Dungbeetlespp.compositionin RILarearesembles10forestmorethan Daviesinpress) loggedarea(Malaysia: conventionally

>

Butterflies,flyingbeetles,canopybeetles,canopyants,leafeaterants, all declinedalongdisturbancegradient termitesandsoilnematodes (Lawtonet al. 1998)

>

(Indonesia, 5 yrs & evenness alldecreased abundance Butterflyrichness, Hill et al. 1995) post-logging:

>

vs. 1° greaterin loggedforestandplantations Cassidinae beetlerichness forestandloggedforestcommunitycomppositionmorelikeplantations Nummelin& Borowiec1991) (Uganda:

>

afterinvasionof pioneerplantsat Opportunisticspeciesincrease expenseof closedforestspp(Hollowayet al. 1992)

>

Ant spp.richness similarin Ioforestand MUSforest40 yrs after treatment(Malaysia: Bolton1998)

Shortgenerationtimes& highfecundity allowrapidrecoveryof effected populations(temperatezone studies: Huhta 1976,Heliovaara& Vaisanen1984; tropics:Ghazoul& Hill in press) Negativecascading effectson insectnutrientcycling)are likely decomposition, (Ghazoul& Hill in press)

Category

Soilorganisms >

Fruitingbody(sporome) ) densityof mycorrhizal fungi higher40 yrs.After MUS treatmentthanin I' forest (Malaysia: Watlinget al. 1998)

Aquatic systems

CommunityAttributes Composition

Structure

>

Function

Mycorrhizalfungispp.richness higherin MUStreatedareathanin 1° forest(Malaysia: Watlinget al. 1998);wood-rottingorganisms maybe better impactindicatorsfor logging& othersilviculturaltreatments Changes to soilpropertiesdirectlyinfluences soilfaunadiversity(review in Camilo& Zou in press)

>

Endogeic & anecicearthwormcommunities littleaffectedby smallscale clearcuts& low frequency(>50 yr intervals)largescale(reviewedin Camilo& Zou in press).

>

Lossof instream& riparianzonediversity;decreased abundance of fishes& benthicinvertebrates intolerantof (a)highsedimentation, (b) shiftsin photosynthesis/respiration ratios,(c) invasive spp(reviewin Pringle& Benstead in press)

>

Alterationsin light& temperatureregimes, streamsedimentloads,turbidity,stream chemistry,hydrology& fluvial geomorphologymaycausecascading effectson aquaticfoodwebs(Pringle& Benstead in press)

Appendix IVBird Responses (densitybased on inter-site comparisons) to Logging in Tropical Forests, Organized by Feeding Guild


51

01

Bird responses(density' basedon inter-site comparisons)to loggingin tropical forests,organized by feeding guild Ulu

Site Logging intensity Recovery (yearssinceharvest) Hunting

Budongo, Uganda 20-80m3 /ha 25-50 no

Ulu

Kibale, Tekam, Segama, Segama, Imatoca, Uganda Malaysia Sabah Sabah Venezuela 2! m3lha 18trees/ha 79m3 lha 90m3 lha 5-8 m3lha 9-10 1-6 25 6-7 3-4 unknown no no no no

PistedeSt -Elie, FrenchGuiana 1Om3lha 10m3/ha 10 1 yes yes

Guild Frugivore

+

nc

+

-

nc

nc

-

Frugivore/insectivore (arboreal)

nc

+

+

+

+

+

nc

nc

-

Frugivore/insectivore(terrestrial)

nc

+

-

-

nc

nc

na

na

Frugivore/granivore Granivore Granivore/insectivore

nc nc nc

nc + +

na na na

na na na

na na na

na + na

na na na

na na na

Insectivore(sallying) Insectivore(terrestrial) Insectivore(arboreal foliagegleaner) Insectivore(understory foliagegleaner)

-

-

-

nc

nc

nc nc nc

nc nc +

-

nc

nc

-

na nc

Insectivore (bark gleaning)

nc

-

-

nc

Insectivore/nectarivore

nc

nc

nc

+

+

+

Predator

nc

+

nc

+

-

na

Predator/frugivore

na

na

-

nc

nc

na

Source

Owiunjiand Plumptre 1998

Dranzoa Johns1989a Nordinand 1995 Zakaria 1997

Lambert et al. 1992

Mason1996

Thiollay Thiollay 1992,1997 1992,1997

Notes: Density(calculated by samemethodwithina study,but differedbetweenstudies).+ = higherfollowinglogging,- = lower followinglogging,nc = no change, PB 0.05. (Adaptedfrom MasonandThiollay,in press;Plumptreet al.,in press;andZakariaand Francis,in press). na= informationnot available;

Appendix V Impacts of Logging (and other silviculture treatments where noted) on the Species Component of Biodiversity in Tropical Forests


53

Impacts of logging (and other silviculture treatments where noted) of the speciescomponent of biodiversity in tropical forests Species Attributes Taxa Vegetation

Structure > Smallersizeclasses mostaffected> by felling,skidding,androad construction > 62% seedling& 59%sapling mortality(Malaysia: Borhanet al. 1987) > S I1I%of treesuprooted(Brazil: Uhl & Guimaraes1989)

17treesdamaged for everytree cut (E.Kalimantan: Abdulhadiet al. 1981) 0 >50% of youngtreeskilled(N. Queensland, Australia:Cromeet al. 1992)

Composition Highgradinglargecommercial trees causedlocalextirpationof Caesalpinia echincata, Ceibapentandra, andAniba duckei;Amazonia(Gentry& Vasquez 1988,GrieserJohns1997) Harvesting figspromotestheir regeneration & maynot havewildlife

)

impactsdue to scarcity of well-formed

>

) )

Largeandsmalltreeskilledwith equalprobabilityJohns1988; Cromeet al. 1992)

>

>

Species w/ type IIl population structuremaybeeasily eliminated(C. Peterspers. comm.)

>

>

Spatiallyclumpedpattern of

>

>

Function Reduced seedavailability & reducedseeddispersalby rodentsof largeseededcommercialspeciesafterlogging(Guyana: Forget& Hammondin press,Hammond& Thomasin press) Fordioeciousspecies,seedcrop decreases with increasing distanceof malesto females(Mack1997) Higherseedlingmortality(esp.invery disturbedareas)in Sabah (Pinardet al. 1996) (iade

l

96

Lowerseedling growth rates(Nussbaum et al. 1995) Reduced densityof adults(i.e. breedingindividuals) 4 fewer flowersper unitarea(C. Peters,pers.comm.) 1% increasein tree mortality3-4 yr post-logging (Silvaet al. 1995, F1 & Camacho1999) Fegan 4-fold increaseintree mortality2 yrs post-logging (Thiollay1992) Moreresourcesavailableto residualtreesb/c of reductionin canopycoverandstem density(Maitre1991);but damaged trees mayneedto useresourcesto healw/ netresultof increasein abortedfruits(Stephenson1981) Potentiallyhigherseedpredationlevels(Schupp1990,C. Peters, pers.comm.)

Temporaryincreaseingrowthratesdependingon extentof canopyopening(WanRazali1989) > Meandbh increment2-3x higherin loggedvs.unloggedJonkers 1987)

conspecifics shiftsto dispersed or randompatterns4 reproductive biologyandlogisticsof future silviculture Primates

>

trees(Bolivia;Fredericksen et al. 1999) > Populations of wild fruit treesare often ) decimatedby destructiveharvesting (Peru: Vazquez& Gentry1989) >

)0- - 60-70%of residual trees damaged by logging(Fox1968; Nicholson1979) >

>

>

Lower growth rates after thinning + selective loggingin (E.

Malaysia: Primacket al. 1989) >

SeeAppendixVI

Lowergrowthratefor Araucaria cunninghmamii (Australia:Enright 1978)

>

Civetdensitiesin loggedforestwere only 2-12yrs post 20%of 1°(Malaysia, selectivelogging,no hunting:Heydon& when

Tree shrewdensititesgreater40 yrs post MUStreatmentthan 10 forest(Malaysia: Laidlaw1998)

>

declineafter Giantforesthogpopulations logging(Davieset a].in press)

>

increasein response Elephantpopulations to logging(Africa& Asia:GrieserJohns 1997)

>

reduced populations (Tragulus) Mousedeer afterlogging(80-100m3/ha,Malaysia: Heydon& Bulloh1997)

& Rodents Marsupials

>

showedvariable Squirrel& rat populations to MUS responses & species-specific Laidlaw 40 yrs post-treatment: (Malaysia, 1998)

Bats

>

Vampirebatdensitiesincreaseif cattle introducedto loggedareasaohns et al. 1985,Wilkinson1985,Johns1988,1992a, Fentonet al. 1992)

Birds

>

SeeAppendixIV

Non-rodent mammals

Herps Insects Soilorganisms

Appendix VI Primate Responses (by feeding guild) to Logging in Tropical Forests

Biodiversity Series

-

Impact Studies

57

Primate responses(by feedingguild) to loggingin tropicalforests;O=no change;- = decreaseafter logging;+ = increaseafter logging UluSegamaNangaGaat

GUILD/ SPECIES Logging Intensity(trees/ha)

Kibabe

Pta da Castanha

Kemasul

Budongo

Lope

Kirindy

Kalinzu

Tekam

Sg.Lalang > 20

>20

5.1 or 7.4

6-25

?

38

55

60

25or 50%

>50

?

II

20-30

20-30

11

12-28

1-50

4-20

1-15

20

10

18

Damagelevels(% tree loss)

32-58

54

5

Years since logging

6-12

0-4

0-12

I

.

Omnivores

+ +

apella Cebus albifrons Cebus Lophocebus albigena CercopithecusIhoesti Cercopithecusascanius cephus Cercopithecus Cercopithecusmedius

mitus Cercopithecus

0

0/-

+1-

+

O_0 + I

0 +

0/-

_

+

0

0

Cercopithecuspogonias nictitans Cercopithecus

Ga/ago Gorilla

s_p

Macaca

spp SPP

Macaca

Macaco MacOca Mandrillus Microcebus Pan Perodicticus Phaner Pongo Saguinus Saimiri

0

. .

0

gorila _

fascicularis nemestrina sphinx

_

0

+

0

0

. +

0

0

spP

trogtodytes potto furcifer pygmaeus mystax

0/.

0

+

+

+

_

+ +

sPP

+

_

Folivores/frugivores

seniculus Alouatto paniscus Ateles Callicebus moloch torguatus Callicebus Procolobus badius guereza Colobus satanus Colobus hosei Presbytis melalophos Presbytis obscura Presbytis rubicunda Presbytis

0 __

+ +

__

0/+

. +

_

+

+

0

0 . _

+ .

.

Frugivores/folivores tars Hylobates muelleri Hylobates lagotricha _ Lagothrix albicans Pithecia References

I

l_l

0

Johns 1989a,b

Dahaban 1996

* Modified from Plumptre and Grieserjohns (in press)

u-

I

+

Johns 1989a,b

+ Laidlaw 1994 Laidlaw 1994Johns 1991b Skorupa 1986, Plumptre & 1988;Weisenrseel Reynolds 1994 et al. 1993; Chapman et al.

_ Ganzhorn White 1992, Howard 1994 1995; 1991; Hashimoto Ganzhorn et al. 1990 1995

Appendix VII Impacts of Logging (and other silviculture treatments where noted) on the Genetic Component of Biodiversity in Tropical Forests

Biodiversity Series

-

Impact Stutdies

61

Impactsof logging(and other silviculturetreatments where noted) on the geneticcomponentof biodiversityin tropical forests Taxa Vegetation

Primates Non-rodentmammals Rodents& Marsupials Bats Birds Herps Insects Soilorganisms

Structure P

_s_

_

GeneticAttributes Composition Geneticdiversity decreasedby ' 5.0-23.4% (logged I yr prior; regeneratedstandsshowed no

Function Outcrossingrates unchangedin Shorealeprosula(Chan 1981, Lee et al. 1996,Wickneswari et al. 1997)& Dryobalanops aromatica(Kitamura et al. 1994)

significantloss);effect on dioecious speciesperhapsunderestimated (Wickneswariet al. 1997)

Outcrossingrates decreasedin Shoreamegistophylla(Murawski et al. 1994a,b);density of mature individualslikely an important factor >

Reducedcross-pollinationrates in Shoreasiamensisafter logging (Ghazoulet al. 1998)and reduced pollination successof Dipterocarpusobtusifoliusafter loggingS. siamensis(Ghazoul 1999)

P

Outcrossing ratesof Carapaspp. were lower after controlled experiments in loggedvs. unloggedforests in FrenchGuiana (Doligez& Joly 1997) but were not significantlydifferent in Carapastands in Costa Rica(Hall et al. 1994)possiblybecause of very high stand densitiesin Costa Rica.

P

Studiesciting genetic erosion of Swieteniamahoganiifrom logginghave not been substantiatedin follow-up studies (reviewed in Lugo 1999)

Glossary' Advanced regeneration: seedlings or saplings present in the understory prior to logging or other silvicultural treatment Aerial logging: a timber yarding system using suspended cables, helicopters, or balloons to lift logs Afforestation: establishment of forests in areas that did not historically support them (e.g., in savannas or drained marshes) Bole: trunk or main stem of a tree Buffer zone: vegetation maintained on the borders of roads, wetlands, or other ecologically sensitive areas to mitigate the impacts of management activities Bulk density: the weight per unit volume of a material (often soil) Carbon sequestration: carbon storage Coppice: sprouting of trees from stumps or roots

compound) interest rate; used to calculate the "net present value" Edaphic: related to or caused by particular conditions in the soil Enrichment planting: increasing the density of desirable species by interplanting, planting in gaps, or planting along cleared lines Fragmentation: the process of breaking once continuous expanses of an ecosystem type (typically forest) into island-like patches in a matrix of other land uses Gap: generally refers to a hole in the canopy created by the death of a canopy tree, but there are also understory gaps and belowground gaps Girdle: to make an incision around a tree trunk at least as deep as the cambium with the intention of killing the tree; if combined with arboricide application then referred to as "poison girdling"

Cutting cycle: the time (years) between stand entries for timber extraction; there can be more than one cutting cycle in a "rotation"

Group selection: harvesting of trees in clusters generally no wider than twice the height of the mature trees to promote regeneration of moderately light-demanding species (a "polycylic" system)

Dendrology: the study of trees including their identification

Hauling: carrying logs by truck (lorrie) from the forest to processing or exporting facilities

Discounting: adjusting a future value by dividing by a function of the (generally

Heartrot: decomposition of the central stemwood of living trees typically due to fungal

BiodiversitySeries- ImpactStudies

63

Biodiversity Conservation in the Context of Tropical Forest Management

infection after mechanical or fire-related damage Heterozygous: having two different alleles at the same locus on homologous chromosomes; an index of genetic diversity High-grading: removal of the best trees often leaving a residual stand dominated by trees of poor form and non-commercial species; "creaming" Highlead yarding: a yarding system in which logs are skidded along the ground to a central point by a cable passing through a block at the top of a tower or spar tree (not to be confused with "skyline yarding") Liana: woody vine Liberation thinning: a silvicultural treatment in which future crop trees are released from competition typically by girdling near neighbors (note: term used differently by many North American foresters) Logging intensity: can refer to either the timber volume or number of trees harvested per unit area Natural forest management: management of forests for timber, non-timber forest products, and environmental services by relying principally on natural regeneration (compare to plantation

forestry)

Reduced-impact logging: a set of techniques designed to avoid excessive damage to soil or to the residual stand during and after timber harvesting; typical components include preplanned skid trails, directional felling, and engineering specifications for stream crossings Reforestation: the recovery of forests in areas that were deforested; compare to "afforestation" Regeneration method: a timber harvesting method that promotes development of a new age class; the principal methods include clearcutting, seed tree, shelterwood, selection, and coppicing Riparian: a terrestrial area bordering a water body Rotation: the period between establishment of regeneration and final harvesting in even-aged stands Shelterwood method: a stand regeneration method that occurs in two phases, a first phase in which enough timber is harvested to promote development of a new age class in partial shade, and a final felling of the remaining mature timber after regeneration is established Silviculture: the art and science of controlling the establishment, growth, composition, and health of forests and woodlands Skidding: yarding logs with a rubber-tired selfpropelled

machine

or bulldozer

("snigging"

in

Australia) Neotropics: American tropics Net present value: the current value of some future cost or benefit Paleotropics: tropical areas in Africa, Asia, Australia, and the Pacific Islands Plantation: a stand of trees established by planting; tree farm 64

Skyline yarding: a log yarding system in which logs are partially or entirely suspended from a taut cable (not to be confused with "high-lead yarding") Stand: a contiguous group of trees with a moreor-less similar history of disturbance, species composition, size-class distribution, and structure Environment Department Papers

Glossary

Succession: the gradual change in structure and composition as an area recovers from disturbance or on previously un-vegetated areas

Yarding: the process of extracting logs from the stump to the roadside, river edge, or other site from which they are hauled

Thinning: a silvicultural treatment designed to reduce stand density

Note

Tractor: can refer to a bulldozer (=powered vehicle with crawler tracks) or a farm tractor


Impact Studies

1.

Based heavily on Helms (1998).

65

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