Practical Conservation Biology

By David D. Lindenmayer and Mark M. Burgman

Practical Conservation Biology covers the complete array of topics that are central to conservation biology and natural resource management, thus providing the essential framework for under-graduate and post-graduate courses in these subject areas. Written by two of the world’s leading environment experts, it is a ‘must have’ reference for environment professionals in government, non-government and industry sectors.

The book reflects the latest thinking on key topics such as extinction risks, losses of genetic variability, threatening processes, fire effects, landscape fragmentation, habitat loss and vegetation clearing, reserve design, sustainable harvesting of natural populations, population viability analysis, risk assessment, conservation biology policy, human population growth and its impacts on biodiversity.

Practical Conservation Biology deals primarily with the Australian context but also includes many overseas case studies. The book is the most comprehensive assessment of conservation topics in Australia and one of the most comprehensive worldwide.

Winner of the 2006 Whitley Award for Best Conservation Text.

• Language: English
• Publisher: CSIRO PUBLISHING
• Release date: Oct 26, 2005
• ISBN: 9780643099463

Book preview

PRACTICAL

CONSERVATION

BIOLOGY

DAVID LINDENMAYER & MARK BURGMAN

© David Lindenmayer and Mark Burgman 2005

All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owner. Contact CSIRO PUBLISHING for all permission requests.

National Library of Australia Cataloguing-in-Publication entry

Lindenmayer, David

Practical conservation biology

Bibliography

Includes index

ISBN 0 643 09089 4

1. Conservation biology – Australia. 2. Nature conservation – Australia.

3. Plant conservation – Australia. 4. Biological diversity

conservation – Australia. 5. Environmental management – Australia.

I. Burgman, Mark A. II. CSIRO Publishing. III. Title

333.95160994

Available from

CSIRO PUBLISHING

150 Oxford Street (PO Box 1139)

Collingwood VIC 3066

Australia

Telephone:  [phone]

Local call:  1300 788 000 (Australia only)

Fax:  [phone]

Email:  [e-mail]

Web site:  www.publish.csiro.au

Front cover

Background image: Photo by David Lindenmayer with permission from the people of the Blackstone Community in Western Australia. Other photos from left to right: Mainland Tiger Snake; Remarkable Rocks, Kangaroo Island, South Australia; Sugar Glider (photo by Mike Greer); Market Garden, Dandenong Ranges.

Back cover

Guanacos, Tierra del Fuego, Chile.

All photos by David Lindenmayer unless otherwise noted.

Set in Minion

Cover and text design by James Kelly

Index by Russell Brooks

Typeset by Thomson Press

Printed in Australia by Ligare

Contents

Preface

Acknowledgements

General introduction

A focus on the Australian environment

Structure of the book

Part I: Principles for conservation

The multifaceted nature of conservation biology

Soulé’s conservation biology principles

The tension between ‘pure’ and ‘applied’ conservation biology

1 Why conserve?

1.0   Introduction

Objectives of conservation

Temporal changes in philosophies and opinions

1.1   Utilitarian value

Consumptive use value

Productive use value

Ecosystem service value

Scientific and educational value

Cultural, spiritual, experiential and existence value

Aesthetic, recreational and tourist use

Impacts of tourism on biodiversity

Summary: utilitarian values

1.2   Intrinsic value

Ecocentric ethic

Biocentric ethic

1.3   Anthropocentric bias

1.4   Custodial responsibility and the precautionary principle

1.5   Conclusions

1.6   Practical considerations

1.7   Further reading

2 What should be conserved?

2.0   Introduction

2.1   Units of conservation

Genetic diversity

Populations

The species concept

2.2   Number of species

Total number of species

New habitats and new species

Sampling methods and new species

Rates of description of new species

Summary: number of species

2.3   Species richness

Problems with the uncritical use of species richness

2.4   Endemism

Causes of endemism

Megadiverse nations and endemism

Endemism and global biodiversity hotspots

Endemism within Australia

2.5   Species diversity: alpha, beta and gamma diversity

2.6   Vegetation structure as a target for conservation

Australian rainforest

Old growth forest

2.7   Conclusions

2.8   Practical considerations

2.9   Further reading

3 Conservation status: classification of threat

3.0   Introduction

3.1   Rarity and conservation status

Components of rarity

Rarity and conservation priorities

Relationships between components of rarity

Realised niches and rarity

Species abundance curve

Explanations for the species curve

Quantifying abundance, range and specificity

Ecological correlates of rarity

Rarity, threat and extinction proneness

3.2   Assessing conservation status

Extinct and presumed extinct species

Qualitative procedures for assessing threat

Rule sets

Point-scoring procedures

Uncertainty in conservation status assessment

Summary: assessing threat

3.3   Threatening processes

3.4   Conclusions

3.5   Practical considerations

3.6   Further reading

4 Protected areas, off-reserve conservation and managed populations

4.0   Introduction

Protected areas

4.1   Categories of protected areas

Other types of protected areas

4.2   Protecting communities and ecosystems

Classifying and protecting ecosystem types: the Interim Biogeographic Regionalisation for Australia

Protecting IBRA regions

Classifying and protecting ecological communities

Ecosystem types, vegetation communities and the adequacy of protection

4.3   Off-reserve conservation

Limitations of a reserve-only focus for biodiversity conservation

Impediments to expanding reserve systems

Intensification of exploitation and downgrading the conservation value of unreserved land

Impacts of external factors on conditions within reserves

Barriers to off-reserve conservation

Summary: off-reserve conservation

4.4   Botanic gardens and zoos

Botanic gardens

Zoos

4.5   Gene banks and storage facilities

Field gene banks

Seed banks

In vitro storage

Ex situ conservation of microbial diversity

4.6   Reintroduction, translocation and captive breeding

Types of relocations

Prevalence of translocation and reintroduction

Translocations, reintroductions and former ranges of species

Effectiveness of reintroduction and translocation strategies

Why reintroductions and translocations fail

Cost and cost-effectiveness of reintroduction strategies

4.7   Conclusions

4.8   Practical considerations

4.9   Further reading

Part II: Impacts

5 Changes in the physical environment

5.0   Introduction

5.1   Land degradation, water resources and salinisation

Land degradation

Water in the Australian environment

Aridity, variability and the Australian biota

Salinisation

5.2   Chemical pollution

Agricultural and other chemicals

Excessive inputs of nutrients into ecosystems

CFC-induced ozone depletion

Other chemical pollutants

Limiting chemical pollution

5.3   Climate change

The human basis for climate change

Predicting future climate change

Impact of climate change on species distribution patterns

Climate change and reserve design

Other impacts of climate change on biodiversity

5.4   Conclusions

5.5   Practical considerations

5.6   Further reading

6 Loss of genetic diversity, populations and species

6.0   Introduction

6.1   Loss of genetic variation

Inbreeding

Outbreeding

Bottlenecks

Hybridisation and swamping

Mutational meltdown

Summary: loss of genetic variation

6.2   Background extinction rates

6.3   Mass extinction events

6.4   Extinction rates in recent history

Extinctions in Australia

6.5   Future extinction rates

6.6   Conclusions

6.7   Practical considerations

6.8   Further reading

7 Changes in species distributions and abundances

7.0   Introduction

7.1   Range contraction and depletion

Mammals

Amphibians

Range contraction and natural distribution and abundance patterns

Migratory species: a special case of range conservation

7.2   Range expansion

7.3   Exotic animals

Exotic vertebrates

Exotic invertebrates

Exotic marine organisms and ballast water

7.4   Exotic plants

Types of weeds

Weeds in Australian plant communities

Rates of naturalisation

Mechanisms of introduction

Weeds and pasture productivity for grazing

Weed dispersal and the impacts of motor vehicles

Environmental impacts of weeds

Weeds and animal populations

Weed control

Prevention

7.5   Australian exports

7.6   Genetically engineered species

Transgenic varieties and genetically modified organisms

Potential benefits of genetically modified organisms

Risks of genetically modified organisms

Assessing the effects of genetically modified organisms

7.7   Pathogens

Cinnamon Fungus

Other diseases

7.8   Conclusions

7.9   Practical considerations

7.10 Further reading

8 Harvesting natural populations

8.0   Introduction

8.1   Native forest harvesting

Definition of forest cover

Early vegetation clearing and the establishment of State forests

Native forest harvesting

Regional Forest Agreement process

Criteria and indicators of sustainability

Forest industry certification

Summary: native forest harvesting

8.2   Plantation forestry

Australian plantations

Why biodiversity conservation within plantations is important

Plantation establishment and biodiversity

8.3   Kangaroo harvesting

History of Kangaroo harvesting in Australia

Data input to guide Kangaroo harvesting

Setting quotas for Kangaroo harvesting

Ethical positions and perspectives on Kangaroo harvesting

8.4   Fisheries

The complexity of fisheries management

Stages of fisheries collapse

By-catch impacts

Cascading impacts of overfishing

Australian fishing industry

Status of Australian fishery stocks

Example of a sustainable fishery

Future issues and approaches to sustainability

8.5   Conclusions

8.6   Practical considerations

8.7   Further reading

9 Vegetation loss and degradation

9.0   Introduction

9.1   Vegetation clearing and habitat loss in Australia

Australia’s contribution to global levels of land clearing and vegetation loss

Past land-clearing patterns in Australia

Clearing by land-use zone

Clearing rates and land tenure

Vegetation types that have been cleared

Land clearing impacts on biodiversity

Dieback

9.2   Mining and urbanisation

Mining

Impacts of urbanisation

9.3   Traditional Aboriginal use and pastoralism

Traditional Aboriginal land use

Pastoralism

9.4   Conclusions

9.5   Practical considerations

9.6   Further reading

10 Landscapes and habitat fragmentation

10.0   Introduction

10.1   Ways that landscapes can be altered

Vegetation cover patterns that arise from habitat loss and habitat fragmentation

Dynamism in the patterns of vegetation cover

10.2   Models of landscape cover

Island model

Nested subset theory

Patch-matrix-corridor model

Habitat-variegation or landscape continuum model

Congruence between the patch-matrix-corridor and continuum landscape models

Limitations in the application of the landscape models

Landscape contour approach

10.3   Ecological processes and species responses to habitat loss and fragmentation

Context for habitat loss and habitat fragmentation

Problems with the term ‘habitat fragmentation’

Five processes associated with landscape change

Habitat loss

Vegetation loss, threshold effects and species loss

Cascading fragmentation effects

Vegetation subdivision, patch isolation and dispersal

Edge effects

10.4   Studying habitat loss and fragmentation

Experiments

‘Natural’ experiments

Observational studies

Modelling

Problems in the way fragmentation is studied

10.5   Forecasting fragmentation effects

Predictive ability, generality and meta-analyses

10.6   Limiting the effects of habitat loss and fragmentation

Limiting and reversing habitat loss

Maintaining habitat quality

Increasing connectivity

Wildlife corridors as a way to maintain connectivity

Other approaches to enhancing connectivity

Reducing edge effects: buffer systems

General principles for landscape management to mitigate habitat loss and fragmentation

10.7   Conclusions

10.8   Practical considerations

10.9   Further reading

11 Fire and biodiversity

11.0   Introduction

11.1   Brief history of fire in Australia

11.2   Types of fire

Wildfire

Prescribed fires

11.3   Response of biodiversity to wildfire

Wildfire and Australian animals

Wildfire and Australian plants

Wildfire and identifying patterns of species responses

11.4   Response of biodiversity to prescribed fire

11.5   Species vulnerability to fire

Animal and plant groups threatened by altered fire regimes

Vegetation communities sensitive to fire

11.6   Spatial variability in fire behaviour: fire refugia, landscape mosaics, and Aboriginal burning patterns

Fine-scale vegetation mosaics and Aboriginal burning

11.7   Fire management and biodiversity conservation

Fire management and conservation of the Eastern Bristlebird and the Ground Parrot

11.8   Studies to examine the effects of fire

Experiments

Observational studies

Modelling

11.9   Ecological theories, fire disturbance and biodiversity conservation

The biological legacies concept and biodiversity

Congruence between human disturbance and natural disturbance: values and limitations

Fire and logging

Intermediate disturbance hypothesis

11.10   Cumulative effects of fire and other disturbance processes

11.11   Fire and reserve design

11.12   The future

11.13   Conclusions

11.14   Practical considerations

11.15   Further reading

12 Demands of the human population

12.0   Introduction

12.1   The world population

Per capita consumption

Impacts of the human population on the environment

Human populations and biodiversity loss

12.2   Demands of the Australian population

Future size of Australia’s population

Energy demands and greenhouse gas production of Australia’s human population

Future Australian populations and future resource use

Australia’s carrying capacity

Australian population and biodiversity loss

12.3   Coastal zone

Uniqueness of the Australian coastal zone

Coastal zone and the human population

Policy problems and solutions in coastal management

12.4   Murray–Darling Basin

Degradation in the Murray–Darling Basin

Biodiversity in the Murray–Darling Basin

Solutions to problems in the Murray–Darling Basin

12.5   Conclusions

12.6   Practical considerations

12.7   Further reading

Part III: Methods of analysis

13 Measuring, managing and using genetic variation

13.0   Introduction

13.1   Types of data

DNA and electrophoresis

Restriction fragment length polymorphism

DNA sequencing

Single nucleotide polymorphism

Randomly amplified polymorphic DNA

Minisatellite and microsatellite analysis

Ribosomal DNA analysis

Mitochondrial DNA analysis

Chloroplast DNA (cpDNA) analysis

Allozyme analysis

Quantitative characters

13.2   Molecular ecology

Understanding social structure

Estimating effective population size

Detecting migration

Effects of genetic change on demographic parameters

13.3   Gene conservation

Spatial structure

Setting priorities for conservation

Managing captive populations

13.4   Conclusions

13.5   Practical considerations

13.6   Further reading

14 Measuring diversity

14.0   Introduction

14.1   Estimating species richness

Species accumulation indices

Ratio estimation

14.2   Detecting rare species

14.3   Species diversity

Alpha diversity

Beta and gamma diversity

A test for change in community structure

14.4   Landscape diversity

14.5   Conclusions

14.6   Practical considerations

14.7   Further reading

15 Identifying habitat

15.0   Introduction

Defining habitat

15.1   Methods for identifying habitat requirements

15.2   Qualitative habitat models

Potential limitations of the HSI approach

Advantages of the HSI approach

15.3   Statistical habitat models

Logistic regression

Reliability measures for statistical models

Making a spatial prediction of potentially suitable habitat

Poisson regression

Summary: statistical habitat modelling

15.4   Envelopes and bioclimatic modelling

BIOCLIM and bioclimatic modelling

Applications of bioclimatic analyses

15.5   Conclusions

15.6   Practical considerations

15.7   Further reading

16 Reserve design

16.0   Introduction

16.1   Ad hoc developments

16.2   CAR reserve system design principles

16.3   Reserve design and biodiversity surrogate schemes

Types of surrogates

Environmental domains

Vegetation maps

Centres of diversity

Potential limitations of surrogates

The need to test surrogates

16.4   Reserve selection

Potential limitations of reserve selection methods

Reserve adequacy

16.5   Reserve design and selection in the real world

Differences in the land base and competing demands for land

16.6   Island biogeography and the design of nature reserves

Problems with the ‘generic reserve design principles’ derived from the island biogeography theory

Why island biogeography theory has limited applicability to reserve design

Summary: island biogeography theory and reserve design

16.7   Conclusions

16.8   Practical considerations

16.9   Further reading

17 Monitoring, assessment and indicators

17.0   Introduction

17.1   Statistical power and the precautionary principle

Statistical power

Power and the precautionary principle

17.2   Management goals, assessment endpoints and measurement endpoints

17.3   Indicators

Species as indicators

Keystone species and indicator species

Ecological redundancy

Guilds as indicators

Problems with indicator species and related concepts

Summary: indicator species

17.4   Selecting indicators

Examples of the selection of suites of indicators

17.5   Conclusions

17.6   Practical considerations

17.7   Further reading

18 Risk assessment

18.0   Introduction

18.1   Estimating extinction rates

18.2   Estimating the likelihood of extinction from collections

18.3   Population management and risk

Types of uncertainty

18.4   Expert judgement

18.5   Population viability analysis

Models for PVA

A model for Matchstick Banksia

Metapopulations

Metapopulations in a PVA framework

Caveats for metapopulation modelling

Minimum viable populations

The limits of population viability analysis

18.6   Conclusions

18.7   Practical implications

18.8   Further reading

Part IV: Management principles for conservation

19 Sustainability and management

19.0   Introduction

19.1   Sustainability

Maximum sustainable yield

Forests

Fisheries

Maximum sustainable yield and uncertainty

Sustainable development

International conventions on sustainability

Globalisation, sustainability and biodiversity conservation

19.2   Adaptive management

A formalised approach to adaptive management

Adaptive management in a political context

Adaptive management in the real world

19.3   Ecosystem management

19.4   Policy and science in conservation biology

19.5   Conclusions

19.6   Practical considerations

19.7   Further reading

Appendix I: Taxonomic names

Appendix II: Glossary

Bibliography

Index

Preface

The title of this book is Practical Conservation Biology because part of its focus is ‘how to do practical conservation biology’. The inclusion of information on the application of particular methods, we believe, sets this book apart from many other conservation biology texts. Much of the book is aimed at an Australian audience, and this is for good reason - most conservation biology texts are written for the North American market. But students and practitioners of conservation biology in Australia often relate best to examples from this country. Moreover, many aspects of conservation in Australia are different from those elsewhere in the world. Despite the Australian focus, the vast majority of methods and the lessons from the case studies are relevant to conservation elsewhere. We hope that conservation biologists outside Australia will also read this text – the exchange of ideas between scientists in different countries reduces the number of wheels that are reinvented.

Writing this book proved to be a monumental task. There is an enormous body of excellent work on conservation biology. Indeed, the literature is now proliferating so rapidly that it is impossible for any one person or small group of authors to stay up to date with it – any book will be out of date before it is published. More than 120 books published in the last five years have the word ‘conservation’ in the title. Tim New has brought out an excellent book titled Conservation Biology. An Introduction for Southern Australia (2000). There are also updated editions of Northern Hemisphere-focused conservation biology texts by Hunter (2002) and Primack (2002) as well as new books from Europe (Sutherland, 2000; Pullin, 2002). There has been a second round of reporting in the Australian State of the Environment series (published in 2001) as well as the National Land and Water Resources Audit (released in 2001 and 2002). There also have been several major reports on the global environment and the state of biodiversity (e.g. Groombridge and Jenkins, 2002; Millennium Ecosystem Assessment, 2005). Much of the information from those reports has found its way into this book. There is also a profusion of information on the Internet and in several chapters we cite the locations of relevant web sites, although readers need to be aware that the addresses of these can change and that information on web sites is of varying reliability.

We apologise to those people whose excellent work we have overlooked. Inevitably, there had to be a considerable body of material that could not be included – often simply because to include it would have made the book too large and unwieldy.

Based on feedback from reviewers on the first edition of this book (titled Conservation Biology for the Australian Environment), two new chapters have been added to Practical Conservation Biology: one on fire and another on landscapes and habitat fragmentation. The first was added because fire has major impacts on biota and is an integral part of the Australian environment. The second chapter on landscapes and habitat fragmentation has been included because this topic has become a major part of mainstream conservation biology.

We hope to receive feedback on the deficiencies of this book, so that if we have sufficient energy to produce a new book, it will be better than this one. But most importantly, we hope that the information presented in this book will stimulate further interest in conservation biology and encourage more Australians to make a contribution to the conservation of the country’s unique biological resources.

David Lindenmayer and Mark Burgman

May 2005

Acknowledgements

This book would not have been completed without the efficient work of Monica Ruibal and Nikki Munro, who found numerous references and constructed many of the tables and figures. We thank Kate Thompson for making the drawing of the giant insects. We are greatly indebted to Joern Fischer and a number of other students who read parts of the book and made many critical comments that vastly improved earlier versions of the manuscript. We are grateful to Claire Drill, Kuniko Yamada and Rebecca Montague-Drake for their work on the figures and for proof-reading drafts of the document. Catherine Hunt did a magnificent job in editing the text.

The authors have made every effort to contact the owners of copyright for figures used in the text. We thank those people who have given us permission to use their work. In some cases, we were not able to find the appropriate person. We apologise for these and any other omissions or oversights in the use of copyrighted material. Any residual mistakes, omissions, and other errors are entirely the work of the authors. DBL is most grateful to all those who kindly provided photographs for this book.

Nick Alexander championed this work and encouraged it to be completed. DBL is greatly indebted to Harvard University (Harvard Forest), who provided a six-month Bullard Fellowship to facilitate the initial stages of book writing.

Finally, we thank our long-suffering partners and families, who have had to deal with the not inconsiderable stresses associated with our book-writing over the years.

General introduction

Since the mid-1980s, conservation biology has become a major research and teaching discipline throughout the world. This book is intended to provide an introduction for advanced undergraduates who are interested in conserving the Australian environment. We introduce methods that are important for detecting and solving conservation problems. We assume familiarity with Mendelian genetics, linear algebra and probability, but not a working knowledge of calculus or computer programming. We expect the reader to have been exposed to the kind of practical statistics that biologists should be taught and are expected to use in a routine way, such as the calculation of confidence intervals and linear regression.

A focus on the Australian environment

We have taken an Australian perspective for several reasons. First, few texts deal adequately with the conservation of the Australian environment. The second reason is that the Australian continent and its biological resources are unique. Australia is the oldest, flattest, and most isolated continent in the world. It supports some of the oldest living life forms on the planet – the 3.5-billion-year-old blue-green algal stromatolites in Shark Bay in Western Australia. Australia’s marine ecosystems support the largest area of coral reef, the longest fringing reef (at Ningaloo in Western Australia), the largest areas of seagrass meadows and the most species-rich marine fish, mangrove and algal assemblages in the world. Australia is the driest inhabited continent, with less than 0.2% of the land surface subject to snowfall, and an even smaller area where snow persists for more than 30 days per year. Australia also has the smallest area of wetland of any continent. The physical environment is also remarkable, because climatic conditions over much of Australia are highly variable over time – more variable than anywhere else (McMahon et al., 1992a). Australia’s soils, and its freshwater and marine systems, are nutrient-depleted. All these factors directly influence the ecology and dynamics of the species that inhabit the continent and the marine systems surrounding it.

Stromatilites at Hamelin Pool in Shark Bay, Western Australia – some of the oldest living life forms on the planet. (Photo by David Lindenmayer.)

The terrestrial flora and fauna of Australia, as well as the continent’s marine and aquatic ecosystems, differ markedly from those elsewhere on the planet. Most taxonomic groups are species-rich and highly endemic (Table A1). Australia is one of only two of the world’s 17 megadiverse countries (i.e. nations that together harbour 60–70% of the earth’s species) that have a developed, industrialised economy. Many terrestrial environments in Australia are dominated by eucalypts (Eucalyptus spp., with between 650 and 820 species depending on taxonomy) and wattles (Acacia spp., with more than 700 species). Many ecosystem processes in Australia are unique; for instance, Australia has a greater proportion of hollow-dependent vertebrates than any other nation, even though the processes of cavity formation in trees are slow because the woodpeckers that promote hollow formation in other parts of the world are absent (Gibbons and Lindenmayer, 2002).

Table A.1. Levels of endemism in Australia and other features of the nations biodiversity. (Data from various sources including Mittermeier et al., 1997; State of the Environment Report, 2001.)

The third reason we have focused on Australia is that it has unique environmental problems. For example, in contrast with other continents, the most pressing threats to the Australian biota are not in tropical rainforests or temperate forests, but in temperate lowland woodlands, grasslands, mallee and heath (Hopper, 1997). The magnitude of salinity problems, with potentially up to 17 million hectares affected by 2050, and the approaches used to counter the problems (see Stirzaker et al., 2002) are rare elsewhere in the world. At a finer scale, within fragmented landscapes, fragment-edge processes such as increased bird nest parasitism by cuckoos, which is common in the Northern Hemisphere, are not apparent in Australia. Similarly, large charismatic carnivorous mammals such as wolves and large cats, which are used as flagship and/or umbrella species in the Northern Hemisphere, are absent from Australia. The largest and most widespread mammalian carnivores are exotic. These and many other differences in conservation biology and management set Australia apart from other continents, regions and nations.

Salt-affected land in South Australia. (Photo by David Lindenmayer.)

The fourth factor contributing to the Australian focus of this book is that unique social and economic factors influence biological conservation here. Australia has the longest-known continuous human culture in existence, with Aboriginal inhabitants being present for at least 40 000 years and possibly 70 000 years. Australia is also one of the most urbanised human societies, with one of the lowest population densities, but one of the highest per capita population growth rates (Smith, 1994; Foran and Poldy, 2002). It has a human population density five times lower than the next least densely populated megadiverse nation, New Guinea (State of the Environment, 2001a). Australia’s per capita energy and resource use is relatively large, even by the standards of developed economies – 200 tonnes of natural resources are moved to support each Australian each year, which is 2½ times the equivalent for a person in the USA and five times that for someone living in Japan (Foran and Poldy, 2002). Thus, Australians have one of the heaviest ‘ecological footprints’ of any people on earth (Wackernagel et al., 1997).

Rock paintings are a key part of indigenous Australia culture – the longest continuous human culture in existence. (Photo by David Lindenmayer with permission from the people of the Blackstone Community in Western Australia.)

High levels of consumption translate into high levels of impact on the environment; in fact, Australia has one of the highest rates of land degradation of any nation (Graetz et al., 1995; Chisholm, 1999; State of the Environment, 2001a). Australia also leads the world in recent recorded mammal extinctions (Short and Smith, 1994; although see Balmford, 1996) and has the highest per capita number of threatened species (Table A2). Similarly, Australia has the highest rate of land clearing of any developed nation (Australian Conservation Foundation, 2001). High levels of land clearing in other megadiverse countries such as Brazil, Mexico, Zaire, Madagascar and Indonesia are associated with rapidly expanding human populations, poverty and migration patterns. Such associations do not hold in Australia’s low-density, affluent society.

Table A.2. Proportion of groups that are nationally extinct, endangered, or vulnerable. (Data from State of the Environment, 2001.)

Structure of the book

This book comprises four broad sections. We anticipate that some people will read the book from beginning to end, whereas others will select sections or methods that interest them. The first two sections deal with general principles and are appropriate for introductory subjects in conservation biology. The third section explores technical issues, and is suitable for advanced students and research workers. The fourth section explores some principles of management for conservation. At the end of each chapter we provide a summary of practical implications, details of scientific papers and books for further reading. Key terms and phrases are highlighted in bold throughout the book and are defined in the glossary (Appendix II). A list of taxonomic names for organisms referred to throughout the book is in Appendix I (note also that the names of taxa are spelled with capitals in this book when they refer to a particular genus or species).

Part I deals with the principles of conservation biology. In it, we outline some of the general areas that underpin the discipline of conservation biology, including the basis for conservation, an exploration of what should be conserved, methods for classifying threats, types of protected areas, and ex situ conservation.

Part II examines human impacts on the natural world. It encompasses changes in the physical environment, threatening processes, loss of genetic variability, loss of species and populations, range changes, the effects of exotic plants and animals, harvesting of natural populations, habitat loss, habitat fragmentation, and fire. Part II concludes with a review of the demands of the human population.

Part III focuses on a small subset of the many methods of analysis for conservation biology. It is relevant to those using analytical methods to solve problems in conservation. The topics covered include measuring genetic variation, habitat analysis, reserve design, bioclimatic modelling, measuring diversity, monitoring, statistical power, indicators, and risk assessment.

Part IV of this book examines some general themes in conservation biology, particularly as they relate to ecologically sustainable development. In it, we build general arguments for conservation and provide a rationale for the focus on sound scientific practices in conservation biology.

Even in a textbook such as this, it is possible to provide only a cursory treatment of topics associated with conservation biology. We are also acutely aware that a number of important topics, relating both directly and indirectly to conservation biology, have not been tackled. We have omitted (among many other topics) geographic information systems, environmental law, national and international legislation, trade, environmental pollution, epidemiology and toxicology.

Part I: Principles for conservation

The multifaceted nature of conservation biology

Conservation biology is the applied science concerned with the management of biological diversity (or bio-diversity). Although biological information is needed to inform decision-making about conservation and natural resource management (Clark, 2002), conservation biology is more than just ecology – much of ecology has no conservation implications. Rather, conservation biology draws on methods and problem-solving skills from many disciplines, including animal behaviour, chemistry, ecology, education, genetics, geography, mathematical demography, medicine, philosophy, policy, political science, sociology and statistics (see Ludwig et al., 2001; Aguirre et al., 2002). In fact, conservation biology could be thought of as a meta-discipline (Brewer, 2001; see Begg and Leung, 2000; Pullin and Knight, 2001; Fazey et al., 2005a).

Soulé’s conservation biology principles

Two decades ago, Soulé (1985) outlined the broad principles that underpin a multidisciplinary approach to modern conservation biology (Figure B1). In essence, the principles state that biodiversity and potential for evolutionary development are intrinsically valuable, and that conservation biology seeks to reduce rates of species extinction and biodiversity loss. Soulé’s (1985) principles influence much of the discussion in this text.

The tension between ‘pure’ and ‘applied’ conservation biology

Conservation biology goes beyond the traditional boundaries of the life and physical sciences to include such things as advocacy (New, 2000; Ludwig et al., 2001). It shares this attribute with epidemiology, in which practitioners believe there is an obligation to influence public policy and decision-making, for the sake of public good. There can be tension between the results of ‘pure’ conservation research and the ‘real-world’, practical applications of conservation biology. This tension is embodied in the trade-offs between generality, precision and realism illustrated in Figure B2. Whelan et al. (2002) describe this as the ‘fire triangle’, with reference to fire ecology research. The fire triangle is based on earlier ecological work by Harper (1982) and Hairston (1989), and is equally relevant to applied conservation biology.

Figure B1. Soulé’s (1985) vision of conservation biology as a multidisciplinary field. Some contributing areas are arguably no longer appropriate, such as island biogeography (see Chapter 10). (Redrawn from Soulé, 1985.)

The philosophy in Figure B2 is important because, although there are some broad generalities in conservation biology, application details are nearly always specific to a species, a group of species, a site, a landscape or a region. Such complexity is the reality of conservation biology. Krebs (1999) highlighted the disappointment of numerous ecologists who have found that their supposed ‘generalities’ did not apply to other systems.

Figure B2. The conservation biology triangle, adapted from fire research (see Whelan et al., 2002) and syntheses of ecological work by Harper (1982) and Hairston (1989).

At the outset of a book on conservation biology, it is important to establish the boundaries of the discipline and to set the framework within which problems are identified and solved. Part I of this book explores, in general terms, why we wish to conserve biodiversity (Chapter 1), what it is we wish to conserve (Chapters 2 and 3), and some of the mechanisms by which conservation can be achieved (Chapter 4).

Box B1

Real world conservation biology: dealing with ‘wicked environmental problems’

At the end of almost all sections of this book there are important caveats about the uncritical application of concepts, methods, equations and general conservation tools. Whether the topic is simple rules for reserve design, ratio estimation for species diversity, indicator taxa, species-loss equations, or habitat suitability indices, we outline the reasons why these approaches are often not ‘magic bullets’ and why their uncritical application could actually deliver poor biodiversity conservation outcomes. If anything, these sentiments highlight the challenges posed by practical conservation biology, and emphasise that the science of conservation biology is inexact, young, and still evolving. Much of what is in this book will be found to be wrong in 20 years; but making mistakes and learning how to better manage ecosystems and conserve biodiversity is a natural part of the scientific process and the evolution of conservation biology as a meta-discipline (Redford and Taber, 2000; Berger et al., 2004).

An additional issue associated with the multidisciplinary nature of conservation biology is that the field often deals with what have been termed ‘wicked environmental problems’. Ludwig et al. (2001) noted that such problems are truly complex in that they have: (1) no definitive formulation, (2) no stopping rules to determine when a problem has been appropriately addressed, (3) multiple legitimate human perspectives, (4) radical uncertainty, and (5) no test for a solution – in part because the solution will be unique in each case and it will not represent the final resolution of a problem. The outcome will often depend on how the problem is framed and by whom (Maddox, 2000). Lindenmayer and Franklin (2002) quoted Bunnell et al. (2003) as stating that ‘forest management is not rocket science – it is much harder’. This sentiment is perhaps even more true of conservation biology.

Chapter 1

Why conserve?

This chapter provides a framework for explaining how different attitudes to environmental management develop and coexist. It explores the different values people hold for biodiversity and the natural environment, such as utilitarian, consumptive, productive use, service, cultural, spiritual, experiential, existence, aesthetic, recreational, and tourist values. The chapter also explores the ethical basis for conservation. The topics discussed in this chapter are central to effective conservation practices because species and communities can be viewed either as objects used to serve human welfare, or as entities possessing value per se.

1.0 Introduction

Conservation biology attempts to conserve the diversity of living things (often termed biological diversity or biodiversity). There are many definitions of biodiversity (Bunnell, 1998; see Box 2.1 in Chapter 2). For the purposes of this book we define it as encompassing genes, individuals, demes, populations, metapopulations, species, communities, ecosystems, and the interactions between these entities.

This definition stresses both the numbers of entities (genes, species, etc.) and the differences within and between those entities (see Gaston and Spicer, 1998). It is similar to the definition of biodiversity proposed by the United Nations Environment Programme (UNCED, 1992):

the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic systems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems.

Most definitions of biodiversity in the literature consider genetic variation within species, the number of species and their relative abundances, variation in the composition of communities at the level of species and at other taxonomic levels, and the diversity of ecosystems and the processes that drive them (Harper and Hawksworth, 1995; Bunnell, 1998). Further discussion of the concept of biodiversity and its definition can be found in Chapter 2.

Objectives of conservation

The objectives of the United Nations Convention on Biological Diversity (1992, cited in CCST, 1994) include:

the conservation of biological diversity, the sustainable use of its components, and the fair and equitable sharing of the benefits arising out of the utilisation of genetic resources.

Conservation is defined by the World Conservation Strategy (IUCN, 1980) as:

The management of human use of the biosphere so that it may yield the greatest sustainable benefit to present generations while maintaining its potential to meet the needs and aspirations of future generations.

The reasons for conserving biodiversity are influenced by underlying human values and philosophies (see Table 1.1). Philosophies differ markedly between individuals and organisations, even those dedicated to conservation (Redford et al., 2002).

Table 1.1. Summary of values and ethical positions underpinning the conservation of biodiversity. (Each of the values is discussed in subsequent parts of Chapter 1.)

Utilitarian value

Consumptive value

Productive use value

Service value

Scientific and educational value

Cultural, spiritual, experiential and existence value

Aesthetic, recreational and tourist use

Intrinsic value

Ecocentric ethic

Biocentric ethic

Future option value

Future discoveries of utilitarian and/or intrinsic value

Precautionary principle

Temporal changes in philosophies and opinions

Dominant philosophies on the use and conservation of biological resources are not static. For example, the Royal Commission (1931) into resource use and human settlement in northern Queensland reported that:

Queensland needs no forestry science for present requirements. There is an abundance and enough of timber for all. Business or common sense management, and not science, is the first requisite. The productive wealth of the country at present suffers from the fact that there are too many, rather than too few trees. That is why ringbarking campaigns are being organised (p. 22).

This sentiment contrasts with that of Gould (1870), who wrote more than a half a century before the Royal Commission:

Australia – a part of the world’s surface in maiden dress, but the charms of which will ‘ere long be ruffled and their true character no longer be seen! Those charms will not long survive the intrusion of the stockholds, the farmer and the miner, each vying with each other to obliterate that which is pleasing to every naturalist; and fortunate do I consider the circumstances which induce me to visit the country while so much of it remained in its primitive state’.

Similarly, Aldo Leopold (1949), recommended that we should:

Quit thinking about decent land-use as solely an economic problem. Examine each question in terms of what is ethically and aesthetically right as well as what is economically expedient. A thing is right when it tends to preserve the integrity, beauty, and stability of the biotic community. It is wrong when it tends otherwise (p. 262).

Leopold was a forester, and one of the leading advocates for environmental protection in the USA. Environmental management practices reflect social and ethical attitudes, and in many instances, practices applied in the past would not be acceptable today. For example, in 1963, the Tallangatta District Conservation Officer in the Upper Murray region of Victoria noted in an unpublished report on grazing conditions in the Tatonga Timber Reserve, under the heading of ‘vermin’, that 55 wombats were killed in one section of the reserve towards the end of 1962, and that the rest of the area would be trapped in 1963. Today, wombats are a protected species.

In the following sections, we outline some current attitudes that motivate conservation. They range from rationalisations of benefits to people, through opportunity costs and ethical considerations of equity, to arguments about the intrinsic worth and moral status of non-human species.

1.1 Utilitarian value

Much of the biodiversity in many countries, including Australia, is on public land or aquatic areas that are subject to government controls. The question of the immediate and long-term use of this land (and its associated biodiversity) is a political and ethical issue. This is evident in the following provocative quote by Jensen (1984):

But I am decidedly and emphatically anti-preservationist, in that I do not condone or support the tying up of vast tracts of useful land (agricultural, grazing and others) in wilderness and parks to become nothing more than breeding grounds for all sorts of pests and vermin, into which people are not permitted to enter, except on foot, and which, unmistakably, create a wasteland of underdevelopment, leaving Australia open to criticism, even invasion, from land-hungry, food-starved people outside these shores.

Given opinions like that of Jensen (1984), there is an imperative to determine the economic and utilitarian (and numerous other) values of biological resources (Redford et al., 2002; Table 1.2). Calculating the economic value of the products and processes of nature is not a simple task (Chee, 2004), and many attempts have been made (Norton, 1987; McNeely, 1988; Bergstrom, 1990; McNeely et al., 1990; State of the Environment, 2001a; Zedler, 2003).

Box 1.1

Valuing ecosystems

Among economists, contingent valuation is perhaps the most popular method for valuing ecosystems and their services (e.g. Tisdell et al., 2005). It uses questionnaires and interviews to elicit preferences and demand functions for environmental goods and services (Garrod and Willis, 1999). It has been applied to a range of environmental issues, including wilderness protection, water quality, and soil erosion. The approach can take into account ownership, access, social context, and perceptual biases (Slovic, 1999). However, the method has several unresolved technical and theoretical problems (Chee, 2004), including the influences of context and framing, and free-riding (in which an individual attains the value of something without outlaying resources or experiencing risk; Garrod and Willis, 1999).

‘Market price’ and ‘productivity’ methods estimate the economic values of ecosystem products or services that are bought and sold in commercial markets, or that contribute to the production of commercially marketed goods (e.g. ‘clean’ water contributes to agricultural productivity). Other approaches include ‘replacement cost’ and ‘substitute cost’ methods. Hedonic pricing means that the economic value of something is determined by how it influences market transactions. A valuer uses market valuations such as house prices to establish values for environmental attributes (e.g. what is a view ‘worth’). Stated preference techniques use direct consumer valuations of environmental values. Most methods rely on converting environmental preferences to monetary preferences, and each method has its own peculiarities (Chee, 2004). Approaches such as multicriteria decision analysis can assist diverse stakeholders to reach consensus on preferences and relative values. There is no easy solution to the problem of valuing ecosystems when values have inherently different scales.

In the first part of the following section, we outline a classification of the utilitarian value of the natural world. It represents one of several ethical perspectives on the environment, and serves to outline the usefulness of conservation practices from a human perspective. We explore some issues associated with utilitarian values, including tourist impacts and the equitable use of genetic resources.

Box 1.2

The value of biodiversity

The environment returns an estimated A$44 trillion in goods and services to human society each year (BirdLife International, 2000). Wood products contribute A$530 billion annually to the world market economy (or about 2% of the world’s total gross domestic product; World Commission on Forests and Sustainable Development, 1999). Losses of biodiversity and flow-on impacts on ecosystem processes could have substantial social and economic costs (Costanza et al., 1997; Pimentel et al., 1997). For example, in 1992 it was estimated that populations of natural parasites and predators accomplished the equivalent of A$130–265 billion worth of pest control in the USA, compared with the A$25 billion expended on artificial control measures such as spraying (Pimentel et al., 1992).

In an Australian context, crude estimates by Jones and Pittock (1997) valued Australian terrestrial ecosystems at A$325 billion per year. The State of the Environment Report (2001) estimated the annual value of some biodiversity-based industries to the nation’s economy. These included: commercial fisheries (A$2.3 billion), woodchips from native forests (A$590 million), honey production (A$300 million), kangaroo harvesting (A$245 million), bushfood production (A$100 million) and wild-flower exports (A$30 million). Biodiversity-related tourism, which depends on the nation’s unique animals, plants and ecosystems is worth several billion dollars.

Consumptive use value

Consumptive use refers to the products of nature that do not pass through a market. The most important direct uses of biodiversity by humans are as food, medicine, fuel and building materials, even though only a very small proportion of the plants and animals that are potentially nutritious are used as food. Consumptive use is usually more diverse, and depends on a much wider spectrum of the available biota than does market-based use. Many people, particularly those who live in traditional ways, for example some Australian Aboriginal and Torres Strait Islander populations, depend directly on the natural environment for live game, firewood, edible plants, medicines, building materials, weapons, transport, cultural and spiritual items, raw materials for other technology, and trade goods.

Table 1.2. Total estimated economic benefits of biodiversity worldwide (from Pimentel et al., 1997).

Consumptive fishing by local Burmese people on Inle Lake in Myanmar. (Photo by David Lindenmayer.)

Consumptive use is a significant part of the livelihood of people in many nations. In Ghana, approximately 75% of the human population depends largely on traditional, natural sources of protein, including fish, insects and snails. Firewood and dung provide more than 90% of the total primary energy needs of Nepal, Tanzania and Malawi (McNeely et al., 1990). As many as 80% of people in developing countries rely on traditional medicines derived from wild plant and animal populations (WCMC, 1992; Population Action International, 2000). Despite their importance, especially to people in developing countries, consumptive use values rarely appear in national income accounts (McNeely et al., 1990; Population Action International, 2000).

Productive use value

Productive use values refer to commercially harvested biological resources. That is, products that pass through the marketplace. Some examples are firewood, timber, fish, animal skins, musk, medicinal plants, honey, beeswax, fibres, gums, resins, oils, construction materials, ornamental plants, animals harvested for game meat, animal fodder, mushrooms, fruits and dyes (Beattie and Ehrlich, 2001; AFFA, 2003a). Biological resources can be taken from natural ecosystems in commercial quantities, and are important in many national economies. For example, drugs derived from rainforest plants had an accumulated net worth of approximately US$150 billion per year in 2000 (Beattie and Ehrlich, 2001). Prescott-Allen and Prescott-Allen (1986, cited in McNeely et al., 1990) estimate that wild species contribute 4.5% to the gross domestic product of the USA. The percentage contribution of wild species to the economies of developing countries is usually higher (Groombridge and Jenkins, 2002).

Wild biological resources also contribute to domesticated production systems (Vavilov, 1949). In particular, native species contribute to pasture, and wild species, especially plants, serve as sources of new domesticates and provide a pool of genetic variation from which new material can be introduced into existing gene pools (Myers, 1990a; Population Action International, 2000). Variety in plant and animal species insures against climate change and catastrophic disease (Myers, 1990a). For example, Wild Rice is the source of resistance to viruses in commercial rice varieties (McNeely et al., 1990), and resistance to rust, a fungal disease common in Wheat, was discovered in the wild relatives of domestic Wheat (Myers, 1993). However, there has been a major loss in the diversity of agricultural genetic resources over the past 50–100 years. Groombridge and Jenkins (2002) reported that only 10% of the Wheat varieties used in 1949 remained 20 years later. Similarly, 80% of the varieties of Apple, Cabbage, Corn, Pea and Tomato were lost between 1804 and 1904.

Figure 1.1. Origins of crops and livestock on a global basis. (Redrawn from Myers, 1990a; Population Action International, 2000.)

Just a few species currently provide most of the food for most people on earth. The productivity of natural resources in most countries is dominated by plant and animal species from other countries and regions (Vavilov, 1949; see Figure 1.1). Of the 20 most important food crops and the 20 most important industrial plant species globally, more than 90% of the germ plasm originates from developing countries (Kloppenburg and Kleinman, 1987; Population Action International, 2000). Wild genetic resources from Central America and Mexico serve the needs of maize growers and consumers globally (Myers, 1990a; Population Action International, 2000). Many of the principal Cocoa-growing nations are in West Africa, whereas the genetic resources on which they depend are found in the forests of western Amazonia. More than 98% of the agricultural produce of the USA and Australia is derived from non-native species. Half the crop production of North America is derived from species originating in Asia or Africa, and 30% of Asia’s crop production involves species from the Americas or Africa (WCMC, 1992; Population Action International, 2000). Statistics such as these raise issues about the ownership of genetic resources, the rights of access to these resources, and mechanisms for the distribution of wealth that are derived from these resources.

Making use of biodiversity depends on knowledge about available resources. Our knowledge of invertebrates is poor (Chapter 6), and yet their potential economic benefit is substantial. Beattie (1994) and Beattie and Ehrlich (2001) provide examples of products developed from invertebrates, ranging from new adhesives to anticoagulants and antibiotics in human medicine (Table 1.3). Some species of spiders produce a type of web that is adapted to capturing fast-flying insects. These webs have many useful properties: they are light, have considerable mechanical strength, and have an ability to absorb large quantities of kinetic energy, thus they have many applications in industry. One of their uses is in the construction of bullet-proof vests, which are packed with spider web (Beattie, 1994; Lewis, 1996; Beattie and Ehrlich, 2001). Invertebrates such as grasshoppers are increasingly being used for food in many countries, particularly in Asia.

Table 1.3. Some economic applications of invertebrates (after Beattie and Oliver, 1994; Beattie and Ehrlich, 2001).

Although only a tiny proportion of invertebrate biodiversity is ever likely to have major, direct economic benefits for humans (Lawton, 1991), conserving them will ensure future opportunities to develop such resources (Beattie and Ehrlich, 2001).

Ecosystem service value

Ecosystem services are the processes by which natural ecosystems sustain human life. They include producing goods such as food, fuels and pharmaceuticals, and services such as biodiversity maintenance and waste assimilation (Daily, 1997b, 2000; Hooper et al., 2005). In general, management goals are developed with ecosystem processes or services in mind. Biodiversity has important service values because it supports ecological functions and ecosystem processes (e.g. see Naeem et al., 1994; McGrady-Steed et al., 1997; Naeem, 1998, 2002; Duffy, 2003; Naeem and Wright, 2003) on which consumptive and productive values depend (Commonwealth of Australia, 2002a). Service values include pollination; gene flow; predation; competition; maintenance of water cycles (see Box 1.3); provision of nurseries for commercial fish species (in mangroves and coral reefs in particular); regulation of climate; soil production and protection; storage and cycling of essential nutrients; and the absorption, breakdown and dispersal of wastes, pesticides and pollutants (Kremen, 2005). Daily (1999) classified these and other ecosystem services into several broad categories:

production of goods such as food, pharmaceuticals, durable materials, energy, industrial products and genetic resources

regenerative process such as cycling and filtration processes

stabilisation processes such as coastal and river bank stability and the control of pest species

life-fulfilling processes such as aesthetic beauty and serenity

preservation of future options such as new goods and services awaiting discovery.

Successful crop cultivation requires several other species in addition to the crop, such as soil micro-organisms and pollinators, and the virtual absence of many others, particularly insect and vertebrate herbivores. The economic value of pollinators can be significant and they can significantly boost agricultural production (De Marco and Coelho, 2004). Coffee production is a useful example: forest-based native pollinators from 1 kilometre or closer can boost yields by as much as 20% (Ricketts et al., 2004). In another example, in the early 1980s, Greathead (1983) estimated that the value of insect-based pollination of commercial palms in Malaysia exceeded US$115 million per year. Nabhan and Buchmann (1997) estimated that the value of native pollinators to the economy of the USA is US$4-6 billion per year.

Box 1.3

Ecosystem services: New York’s water supply

On average, a 0.06-hectare area of clean uninhabited water catchment is needed to supply each person living in an urban environment with good-quality water (Foran and Poldy, 2002). The more modified a catchment (by roads, for agriculture etc.), the greater the area that is needed to produce a fixed volume of water, the lower the quality of the water, and the higher the treatment costs.

The economic values of ecosystem services are illustrated by the costs of water treatment versus well maintained water catchments for the city of New York. Water treatment plants to supply the city have been estimated to cost A$8–10.5 billion, with annual costs of A$400 million for upkeep and maintenance. In contrast, the 20 000 hectares of land purchased to produce the same amount of water and improve water catchment coverage in the Catskill/Delaware and Croton catchments in north-eastern USA cost much less than a quarter of this – less than A$3 billion (Chichilnisky and Heal, 1998). Notably, similar approaches to set aside forest areas to maintain water quality (and reduce the need for major water treatment works) were taken for the water supply of Boston and neighbouring cities many decades earlier. Entire towns were relocated as part of closing the Quabbin Water Catchment in western Massachusetts to urban and agricultural development.

Large areas of former urban settlements were purchased in the Quabbin Reservoir region to ensure the quality of water catchments that provide water to Boston and surrounding areas. Water production from the forested catchments is an important ecosystem service for many people in the region. (Photo courtesy of Les Campbell and Alfredo’s Photographic Gallery, Amherst, Massachusetts.)

The growth of trees for timber production often depends on the presence of symbiotic fungi (Eldridge et al., 1994). The control of the majority of potential crop pests and disease carriers depends on ecological processes such as predation. Extensive stands of natural vegetation are central components of systems that regulate ozone, oxygen, carbon dioxide and other gases in the atmosphere.

Wetlands have major ecosystem service value. Zedler (2003) estimated that although wetlands cover less than 1.5% of the planet’s surface, they generate as much as 40% of the world’s renewable ecosystem services. Some of the key services they provide and the associated monetary values of these are presented in Table 1.4. There are equivalent estimates for Australian aquatic ecosystems. For example, the rivers, wetlands and floodplains of the Murray–Darling Basin in Queensland, the Australian Capital Territory, New South Wales, Victoria and South Australia have been estimated to provide A$187 billion in ecosystem services (Thoms and Seddon, 2000).

Table 1.4. Estimated values of ecosystem services from wetlands*. (Modified from Zedler, 2003, and based on Costanza et al., 1997.)

*All shallow-water habitats (tidal marshes and mangroves, swamps and floodplains, estuaries, seagrass/algal beds, and coral reefs) are included in the calculations.

The net worth of a proposal for resource development is determined in part by the environmental consequences of the action to undertake the development (Morton et al., 2002). Ecosystem service values are highlighted when ecosystems become degraded to the point that the economics of restoration is measured in dollar terms. Highly degraded ecosystems are not effective providers of goods or services, and they can be very costly to rehabilitate (State of the Environment, 2001a). One of the problems of the ecosystem services concept is that values are often not recognised until they become impaired (McIntyre et al., 2002). The treatment of land degradation in Australia, for example, has current direct costs of hundreds of millions of Australian dollars annually, possibly even billions of dollars (Madden et al., 2000). The annual costs of secondary salinity (in terms of lost agricultural production and remedial treatments) within eight subcatchments in the Murray–Darling Basin is up to A$300 million (Wilson, 2000; see Chapter 5).

Ecosystem service arguments are not, on their own, a sufficient reason to conserve all forms of biodiversity: only a small proportion of species actually provide useful services (Hooper et al., 2005). The degree to which a species that provides ecosystem functions can be substituted by different species is related to the concept of ecological redundancy (Walker, 1992; see Chapter 17). In fact, a relatively small number of species may be necessary for ecosystems to function successfully. However, given our current limited understanding of ecological processes, it is very difficult to say which species are necessary and which are superfluous (see Ellsworth and McComb, 2003, for a study of the hypothesised impacts resulting from the loss of the Passenger Pigeon in North America). The Thylacine in Tasmania is an example of possible ecological redundancy: to the best of our knowledge, the loss of this charismatic large carnivore has not compromised any ecosystem service. This is not to say this species had no ecological role or that, if it still persisted, attempts to conserve it would be unimportant; rather, no particular service value is apparent, and arguments for its conservation would need to consider other values. For instance, Beattie and Ehrlich (2001) contend that so-called redundant species insure ecosystem services against the loss of important species.

Box 1.4

Ecosystem services and option values (after FAO, 2003b).

Endod, also commonly known as the African Soap Berry, is a perennial plant that has been cultivated for centuries in many parts of Africa, where its berries are traditionally used for laundry soap and shampoo. In 1964, the Ethiopian biologist Aklilu Lemma observed that downstream from where people were washing clothes with Endod berries, dead snails were found floating in the water. Further research revealed that sun-dried and crushed Endod berries are lethal to all major species of snails, but do not harm other animals or people, and are completely biodegradable.

For Africa, where one of the most serious human diseases, schistosomiasis, is transmitted by freshwater snails, discovery of a low-cost and biodegradable lumicide (a chemical that kills snails) represented a major breakthrough. According to the World Health Organization, more than 200 million people are infected with schistosomiasis, and it kills an estimated 200 000 people every year. With support from international donors, Endod is undergoing further toxicological studies to ensure its safety. Dr Lemma views Endod as a product of traditional knowledge that can be developed by and for African communities.

Scientific and