Tropical Conservation Biology E-Book

Navjot S. Sodhi

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 697

Veröffentlichungsjahr: 2013

Beschreibung

This introductory textbook examines diminishing terrestrial and aquatic habitats in the tropics, covering a broad range of topics including the fate of the coral reefs; the impact of agriculture, urbanization, and logging on habitat depletion; and the effects of fire on plants and animal survival.

• 
  
• Includes case studies and interviews with prominent conservation scientists to help situate key concepts in a real world context
  
• Covers a broad range of topics including: the fate of the coral reefs; the impact of agriculture, urbanization, and logging on habitat depletion; and the effects of fire on plants and animal survival
  
• Highlights conservation successes in the region, and emphasizes the need to integrate social issues, such as human hunger, into a tangible conservation plan
  
• Documents the current state of the field as it looks for ways to predict future outcomes and lessen human impact

“Sodhi et al. have done a masterful job of compiling a great deal of literature from around the tropical realm, and they have laid out the book in a fruitful and straightforward manner…I plan to use it as a reference and as supplemental reading for several courses and I would encourage others to do the same.” Ecology, 90(4), 2009, pp. 1144–1145

Leseprobe

Contents

Preface

Acknowledgements

1 Diminishing Habitats in Regions of High Biodiversity

1.1 Loss of native habitats

1.2 Drivers of habitat loss

1.3 Biodiversity hotspots

1.4 Summary

1.5 Further reading

2 Invaluable Losses

2.1 Environmental filters

2.2 Precipitation and temperature regulation

2.3 Water purification

2.4 Protecting catchments and soils

2.5 Forests and floods

2.6 Nitrogen flux

2.7 Eutrophication

2.8 Nature’s pharmacy and goods

2.9 Human health and nature

2.10 Ecosystem services from nature

2.11 The direct economic value of nature

2.12 The role of nature in human culture

2.13 Loss of knowledge

2.14 Summary

2.15 Further reading

3 Broken Homes: Tropical Biotas in Fragmented Landscapes

3.1 Theoretical premises of fragmentation

3.2 Abiotic and geometric components of fragmentation

3.3 Biotic effects of fragmentation

3.4 Long-term fate of fragments

3.5 Edge effects

3.6 Vulnerability to fragmentation

3.7 Importance of matrix

3.8 Increasing fragment connectivity

3.9 Summary

3.10 Further reading

4 Burning Down the House

4.1 Forest fires

4.2 Burning savannas

4.3 Tropical fires in the global context

4.4 Fire modelling and mitigation

4.5 Summary

4.6 Further reading

5 Alien Invaders

5.1 What are invasive species?

5.2 Invasive species in tropical realms

5.3 Managing and controlling invasive species

5.4 Summary

5.5 Further reading

6 Human Uses and Abuses of Tropical Biodiversity

6.1 Bush meat crisis

6.2 Captivity trade

6.3 Medicinal and other uses

6.4 Commercial exploitation

6.5 Nuisance control

6.6 Summary

6.7 Further reading

7 Threats in Three Dimensions: Tropical Aquatic Conservation

7.1 Tropical fisheries exploitation

7.2 Coral reefs in peril

7.3 Marine reserves

7.4 Megafauna

7.5 Tropical freshwater ecosystems – water for life

7.6 Where marine and freshwater habitats merge: coasts and estuaries

7.7 Summary

7.8 Further reading

8 Climate Change: Feeling the Tropical Heat

8.1 Overwhelming evidence for human-mediated climate change

8.2 Past evidence for climate change effects on tropical biodiversity

8.3 Effects of recent and projected anthropogenic climate change on tropical biotas

8.4 Fighting climate change

8.5 Summary

8.6 Further reading

9 Lost Without a Trace: the Tropical Extinction Crisis

9.1 Defining ‘extinction’

9.2 Historic extinctions

9.3 Extinction rates

9.4 Case studies of tropical extinctions

9.5 Extinction lags

9.6 Extinction drivers

9.7 Extinction proneness

9.8 Extinction and the perturbation of ecological processes

9.9 Biotic resilience

9.10 The future of tropical biodiversity

9.11 Summary

9.12 Further reading

10 Lights at the End of the Tunnel: Conservation Options and Challenges

10.1 Protected areas are critical for tropical conservation

10.2 Poor governance as a threat to tropical biodiversity

10.3 Improving logging practices

10.4 Livelihoods and conservation

10.5 Conservation education and advocacy

10.6 Better technologies

10.7 Good examples of tropical conservation

10.8 Organizations assisting with tropical conservation

10.9 Restoration, reintroductions and urban management

10.10 Role of sound biological science in tropical conservation

10.11 Summary

10.12 Further reading

References

Index

© 2007 by Navjot S. Sodhi, Barry W. Brook and Corey J. A. Bradshaw

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1   2007

Library of Congress Cataloging-in-Publication Data

Sodhi, Navjot S.Tropical conservation biology / Navjot S. Sodhi, Barry W. Brook, Corey J. A. Bradshaw.

p. cm.Includes bibliographical references and index.ISBN 978-1-4051-5073-6 (pbk. : alk. paper) 1. Conservation biology–Tropics–Textbooks. I. Brook, Barry W. II. Bradshaw, Corey J. A. III. Title.QH77.T78.S63 2007333.95'160913–dc222007009687

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Preface

Habitat loss and fragmentation, overexploitation of species and environmental degradation are operating on a massive scale worldwide, and these are the processes fuelling the current extinction crisis. These human impacts on the biosphere predict a grim future for global biodiversity, especially considering that in many regions the rates of destruction and modification are accelerating. Although the temperate regions of the earth suffered severely from human encroachments in the ancient and recent past, the present-day and future biodiversity crisis loom largest in the tropics. This is especially important in terms of global biodiversity conservation because it is in the tropics that the largest tracts of still-pristine habitat, the greatest species diversity and the richest centres of endemism are found. The mounting threats to tropical biodiversity require conservation practitioners to make urgent conservation decisions. As such, it is critical to document the current state of tropical biodiversity, determine possible ways to protect it and synthesize the vast body of scientific research relevant to tropical regions in a concise, yet comprehensive, format. It was with these aims that we wrote Tropical Conservation Biology – the first book of its kind to focus exclusively on conservation issues in the tropics. A brief summary of the contents by chapter follows:

Chapter 1: Diminishing habitats in regions of high biodiversity. We report on the loss of tropical habitats across the tropics (e.g. deforestation rates). We also highlight the drivers of habitat loss such as human population expansion. Finally, we identify the areas in immediate need of conservation action by elucidating the concept of biodiversity hotspots.

Chapter 2: Invaluable losses. We discuss the utilitarian role of tropical forests in maintaining soil stability, regulation of hydrological processes and climate and carbon sequestration, especially in relation to the importance of ecosystem servicing offered by nature to humanity (e.g. pollination and catchment protection). We also highlight the evolutionary uniqueness, irreplaceability and intrinsic value of nature that is being eroded by habitat and species loss.

Chapter 3: Broken homes: tropical biotas in fragmented landscapes. Owing to massive deforestation and forest degradation, fragmentation is one of the major drivers of species loss in the tropics. We discuss the theoretical premises upon which the importance of habitat fragmentation are based (e.g. negative edge effects and meta-population dynamics). We then exemplify various concepts using empirical information and a wide range of examples.

Chapter 4: Burning down the house. Prolonged drought and poor land use decisions have made many tropical landscapes vulnerable to fire, thus creating a negative feedback cycle that is damaging at both local (e.g. habitat loss) and global scales (e.g. atmospheric pollution). We describe the effects of fire on tropical biotas and how it interacts with other drivers to exacerbate threats.

Chapter 5: Alien invaders. We report on the documented impacts of invasive species on tropical biotas. We describe the process of invasion and the factors that affect ‘invasiveness’ (of both the invading organism and the invaded habitat). We then described a range of documented impacts of invasive species in tropical regions.

Chapter 6: Human uses and abuses of tropical biodiversity. Tropical biodiversity is under heavy threat from anthropogenic overexploitation (e.g. harvest for food or live specimens for the pet trade). For example, wild (‘bush’) meat hunting is imperilling many tropical species as expanding human populations in these regions seek new or long-favoured sources of protein and potentially profitable new avenues for trade. Here we highlight the effects of human exploitation on tropical biodiversity and the unsustainability of current practices.

Chapter 7: Threats in three dimensions: tropical aquatic conservation. This chapter expands on the major marine and freshwater conservation issues plaguing tropical regions. We focus on the impacts of overfishing, water pollution and climate change on the astonishing biodiversity supported by marine and freshwater ecosystems.

Chapter 8: Climate change: feeling the tropical heat. We summarize the main lines of evidence for the biotic response to climate change in the tropical realm – past, present and future. Examples are drawn from studies on local populations through to investigations of pantropical ecosystems. Finally, we discuss options for mitigating the worst of climate change’s predicted effects on tropical biodiversity.

Chapter 9: Lost without a trace: the tropical extinction crisis. We first discuss the empirical evidence for and controversies surrounding current and predictive extinction estimates. We then provide case studies of both local population and species extinctions from the tropics and extract generalities of extinction trends in this region. We also discuss the species traits correlated to extinction proneness or vulnerability of species to decline due to human encroachment in mega-diverse tropical ecosystems.

Chapter 10: Lights at the end of the tunnel: conservation options and challenges. We make pragmatic recommendations for the protection of existing biodiversity. We report on the state, adequacy and complementarity of current protected areas, and discuss the minimum preserved areas required to protect adequately biodiversity at national, regional and global scales. We stress the need to consider the social issues (e.g. human hunger) in order to achieve effective conservation objectives by highlighting examples of conservation successes in different regions of the tropics.

We have also provided a short biography of some of the world’s most eminent conservation scientists within a special Spotlight section in each chapter: Norman Myers (Chapter 1), Gretchen Daily (Chapter 2), William Laurance (Chapter 3), Mark Cochrane (Chapter 4), Daniel Simberloff (Chapter 5), Bruce Campbell (Chapter 6), Daniel Pauly (Chapter 7), Stephen Schneider (Chapter 8), Stuart Pimm (Chapter 9) and Peter Raven (Chapter 10). These biographies are followed by a brief set of questions and answers that focus on some of the most pertinent and pressing issues in tropical conservation biology today. It is our intention that readers of Tropical Conservation Biology will benefit from the knowledge and be inspired by the passion of these renowned conservation experts.

In summary, we have chosen to emphasize the biological aspects of biodiversity conservation, rather than the social or political processes that drive human behaviour. Regardless, the book should not be viewed as a resource solely for biologists – it also contains important information on how natural resource managers, politicians and policy makers can mitigate many of the negative effects of an increasingly human-dominated planet. We have strived overall to present the book’s content so that it will appeal to advanced undergraduate and postgraduate students, scientists and managers with an interest in tropical conservation biology. It is with this general objective that we hope you will find Tropical Conservation Biology interesting, useful and instructive.

Acknowledgements

Funding for research for this book was provided by the National University of Singapore (R-154-000-264-112), Charles Darwin University and the Australian Research Council. David Bowman, Bruce Campbell, Robin Chazdon, Richard Corlett, Tony Cunningham, Robert Dunn, Tim Flannery, Lian Pin Koh, Kelvin Peh, Mark Meekan, Hugh Tan and Cagan Sekercioglu reviewed individual chapters and provided helpful and insightful recommendations for improvement. David Bickford read the entire manuscript and made very valuable suggestions. Matthew Lim provided invaluable assistance in collating material and references, and preparing figures and diagrams. Karah Wertz helped in designing the book’s cover. The scientists featured in each chapter’s Spotlight took the time to provide their expert opinions and biographies: Bruce Campbell, Mark Cochrane, Gretchen Daily, William Laurance, Norman Myers, Daniel Pauly, Stuart Pimm, Peter Raven, Stephen Schneider and Daniel Simberloff. Our sincerest thanks to all listed above, and our families for their support.

1

Diminishing Habitats in Regions of High Biodiversity

In this chapter, we review the loss of native habitats across the tropics: the region that lies between the Tropics of Cancer and Capricorn, i.e. 23.5° north and south of the equator (Figure 1.1). The word ‘tropics’ is derived from the Greek word tropos meaning ‘turn’. The average annual temperature of the tropics is higher and the seasonal change in temperature is less pronounced than in other parts of the world because the tropical zone receives the rays of the sun more directly than areas at higher latitudes. The seasons in the tropics are marked not by large temperature fluctuations, but by the combination of winds taking water from the oceans and creating seasonal rains, called monsoons, over the eastern coasts. Several different climatic types can be distinguished within the tropical belt. Distance from the ocean, prevailing wind conditions and elevation are all contributing elements. Tropical highland climates, which have some characteristics of temperate climates, also occur where high mountain ranges are located. The tropics are the world’s largest reservoirs of humid forests (Amazon, Congo Basin and New Guinea); the immense vegetative growth of these lush ‘rain forests’ is attributable to the monsoon rains. Owing to decreasing rainfall towards the northern and southern limits of the tropics, climatic conditions favour low-latitude savanna, steppe and desert biomes. High temperatures and abundant rainfall make rubber (Hevea brasiliensis), tea (Camellia sp.), coffee (Coffea robusta and C. arabica), cocoa (Theobroma cacao), spices, bananas (Musa spp.), pineapples (Ananas sp.), oils and timber the leading agricultural exports of tropical countries.

Ironically, the tropical region where two-thirds of the world’s biodiversity is found is also the backdrop of massive contemporary loss of native habitats, mimicking the historical land conversion witnessed over the past few centuries in Europe and the temperate regions of North America and Australia. As a result of this mega-rich biodiversity and unprecedented loss of habitats, the tropical region has obviously attracted a high level of interest from conservationists. We first present an overview of habitat loss, namely in rain forests, mangroves and tropical savannas and limestone karsts, and then follow with a report on the known and postulated drivers of native habitat loss in the tropics. Finally, we identify the areas in immediate need of conservation action by discussing the concept of biodiversity hotspots.

Figure 1.1 A map of the world showing the tropics and the distribution of ‘biodiversity hotspots’ outside (grey circles) and within (white circles) the tropics (shaded region): 1, Atlantic forest; 2, California floristic province; 3, Cape Floristic region; 4, Caribbean islands; 5, Caucasus; 6, Cerrado; 7, Chilean winter rainfall – Valdivian forests; 8, coastal forests of eastern Africa; 9, East Melanesian islands; 10, eastern Afromontane; 11, Guinean forests of west Africa; 12, Himalaya; 13, Horn of Africa; 14, Indo-Burma; 15, Irano-Anatolian; 16, Japan; 17, Madagascar and Indian Ocean islands; 18, Madrean pine–oak woodlands; 19, Maputaland–Pondoland–Albany; 20, Mediterranean basin; 21, Mesoamerica; 22, mountains of Central Asia; 23, mountains of southwest China; 24, New Caledonia; 25, New Zealand; 26, Philippines; 27, Polynesia–Micronesia; 28, southwest Australia; 29, Succulent Karoo; 30, Sundaland; 31, tropical Andes; 32, Tumbes–Chocó-Magdalena; 33, Wallacea; 34, western Ghats and Sri Lanka. (After conservation.org. Copyright, Conservation International.)

1.1 Loss of native habitats

If human impact on the natural environment continues unabated at its present rate or increases in severity, then by the turn of the century the resulting changes in land use will have exerted a profound and irreversible effect on tropical biodiversity (Sala et al. 2000). Habitat loss will probably have far greater effects on terrestrial ecosystems in the tropics than other drivers such as climate change, elevated carbon dioxide (CO2) levels and invasive species (Sala et al. 2000). However, among these factors there are likely to be large and complex interactions that exacerbate the foreseen problems. Rain forest loss, degradation and fragmentation are the most widely publicized examples of habitat loss in the tropics; indeed, human activities, such as logging, are degrading and destroying tropical rain forests at a rate that has no historical precedence (Jang et al. 1996; Whitmore 1997; W.F. Laurance 1999). Given that the vast majority of the earth’s terrestrial biodiversity is harboured in these threatened and little-studied biomes (E.O. Wilson 1988; Myers et al. 2000; Sodhi and Liow 2000), they are critical for conservation.

1.1.1 Rain forest depletion

Tropical forests cover 7% of the earth’s land surface, yet they support over 50% of described species, plus a large number of undescribed taxa (W.F. Laurance 1999; Dirzo and Raven 2003). They are also critical for global carbon and energy cycles [Intergovernmental Panel for Climate Change (IPCC) 2002]; therefore, tropical forests are not only crucial for biodiversity conservation, they also play pivotal roles in moderating global climate change. Despite this importance, more than 40% of original tropical forests have been cleared in Asia alone (Wright 2005).

The United Nations Food and Agriculture Organization (FAO) has reported that countries with the largest annual net forest losses between 2000 and 2005 are all situated in the tropics (FAO 2005). These countries include Brazil, Indonesia, Sudan and Myanmar, and they collectively lost 8.2 million hectares (ha) of forest every year between 2000 and 2005 (FAO 2005). W.F. Laurance (1999) used data provided by the FAO (1993) on forest cover change from 1980 to 1990 and estimated that 15.4 million ha of tropical forest is destroyed every year, with an additional 5.6 million ha being degraded through activities such as selective logging. Overall, an average of 1.2% of existing tropical forests is degraded or destroyed every year (Whitmore 1997; W.F. Laurance 1999). In terms of absolute loss of area, forest conversion is the highest in the neotropics (South and Central America: 10 million ha/year), followed by Asia (6 million ha/ year) and Africa (5 million ha/year). However, if we consider forest conversion relative to the existing forest cover in the region, Asia clearly tops the list (W.F. Laurance 1999) (Figure 1.2), with 1.5 million ha of forest removed each year from the four main Indonesian islands of Sumatra, Kalimantan (Indonesian Borneo), Sulawesi and West Papua (Indonesian New Guinea) alone (DeFries et al. 2002). Even the so-called ‘protected forests’ in the tropics are not safe from plunder – of 198 protected areas surveyed, 25% have been losing forests within their administrative boundaries since the 1980s (DeFries et al. 2005).

Figure 1.2 Relative and absolute rates of forest conversion in the major tropical regions throughout the decade of the 1980s. (After W.F. Laurance 1999. Copyright, Elsevier.)

Worryingly high as they are, whether the FAO values are accurate is controversial because they may fail to include catastrophic events (such as the vast 1997–98 forest fires that occurred in Indonesia) and may erroneously include forestry plantations as native forest cover (Matthews 2001; Achard et al. 2002). Deploying remotely sensed satellite imagery, Achard et al. (2002) reported that tropical forest loss may be much lower (5.8 million ha/year) than FAO estimates. Yet even Achard et al.’s estimates have being questioned. It has been argued that their lower estimates of forest loss may be unrepresentative, owing to the fact that they sampled only 6.5% of the humid tropics (Fearnside and Laurance 2003). Nevertheless, despite the different methods used, Achard et al. (2002) also found, as reported earlier by W.F. Laurance (1999), that rates of deforestation and forest degradation are highest in Asia (Figure 1.3).

The expansion of agriculture in the humid tropics is the main culprit in this devastating forest loss, with more than 3 million ha of forest converted annually by this activity (Achard et al. 2002). Although native forest loss in tropical Latin America seems to be decelerating, in a particularly disconcerting trend it continues to accelerate in tropical Asia (Matthews 2001) (Figure 1.4). This trend is further corroborated by a satellite imagery study of Latin America, tropical Africa and Asia by M.C. Hansen and DeFries (2004), who reported that deforestation appears to be accelerating in the last two regions (Figure 1.5). Depending on factors such as soil fertility and proximity to remnant forests (i.e. seed source), forest regeneration can proceed in abandoned areas following disturbance (Chazdon 2003). These secondary forests could be crucial for global carbon cycles and conservation of some forest biota (Wright 2005). However, about a quarter of regenerating forests are also being lost in tropical Asia and Africa (M.C. Hansen and DeFries 2005), with an increase of this forest type found only in Latin America (Figure 1.5).

There has also been controversy as to whether the global deforestation rate is subsiding over time. FAO data show that globally there has been a 31% decrease in the deforestation rate over the past two decades. But a study by M.C. Hansen and DeFries (2004) showed that deforestation has, in reality, accelerated by the same amount during the same period. Wright and Muller-Landau (2006) argue that the deforestation rate will slow down in the future due to a decrease in human population growth and increasing migration to urban centres. They argue that such changes in human demographics will be conducive to forest regeneration. However, Brook et al. (2006a) dispute this scenario because of decoupling between rural and urban human populations (Figure 1.6); even if deceleration does occur, it may be a little too late to stop the mass extinction of biodiversity in the tropics caused by the momentum of past habitat loss (see Chapter 9).

Figure 1.3 Mean annual estimates of deforestation in the humid tropics from 1990 to 1997. (Data derived from Achard et al. 2002.)

Figure 1.4 Worsening deforestation rates in all tropical regions except Latin America. (Data derived from Matthews 2001.)

Figure 1.5 Positive increase in rate of deforestation (filled bars) and decrease in rate of afforestation (blank bars) in tropical Africa and Asia, with only Latin America showing opposite trends. (Data derived from M.C. Hansen and DeFries 2004.)

Globally, 0.8% of native tropical forests (primary and secondary forests, excluding plantations) are likely to be lost each year (Matthews 2001), and in countries plagued by civil war, such as Burundi and Rwanda, the rates of loss can be much higher (Table 1.1). Perhaps most dramatically, it has been estimated that, by 2010, human actions will have caused almost complete destruction of native lowland (< 1000 m elevation) forests from the hyper-biodiverse regions of Sumatra and Kalimantan (Jepson et al. 2001). Such a massive loss of habitat will almost certainly have profound incidental effects on the region’s spectacular megafauna, such as the Sumatran rhinoceros (Dicerorhinus sumatrensis), Sumatran tiger (Panthera tigris sumatrae) and Asian elephant (Elephas maximus). Tropical countries with the highest deforestation rates (> 0.4% deforestation annually) usually have a large percentage of the remaining dense forests (> 80% canopy cover) near deforestation activities, thus indicating that these areas also remain highly vulnerable to deforestation (M.C. Hansen and DeFries 2004) (Figure 1.7).

Figure 1.6 Trends in rural and urban human population growth in the world’s developing countries. Vertical dashed line separates past and projected figures. (After Brook et al. 2006a. Copyright, Blackwell Publishing Limited.)

The lowland tropical rain forests are particularly imperilled owing to their ready accessibility to an expanding human population and their increasing conversion to logging concessions, agricultural land and urban areas (Kummer and Turner 1994). In addition to this widespread forest type, other forest types also existing in the tropics are being destroyed (Whitmore 1997; Figure 1.8). For example, montane/submontane (usually > 1000 m elevation) rain (cloud) forests provide timber, fuel wood, soil and catchment protection. This forest type makes up 12% of the existing tropical forests worldwide, and it is currently being cleared at a rate twice that of the global average [Long 1994; Whitmore 1997; IUCN (The World Conservation Union) 2000]. In fact, montane forests are lost at a relatively higher annual rate than lowland tropical forests (Figure 1.9; Whitmore 1997). Montane forests, because of their unique environmental conditions (e.g. cooler temperatures), support a high degree of endemism. For example, the proportion of endemic moths is at least twice as high in montane forests than in their lowland counterparts in Malaysian Borneo (Chey 2000). Montane forests have a low recovery potential following disturbance (Ohsawa 1995; Soh et al. 2006). However, despite their fragility and high endemism, human activities continue to threaten these vulnerable forests (Ohsawa 1995; IUCN 2000).

Eighty-five per cent of global forest loss occurs in tropical rain forests (Whitmore 1997). However, the tropics also contain seasonal, dry or monsoonal deciduous forests. These generally lie below 1000 m elevation in regions such as Central America, Madagascar and Asia (Thailand) (Ruangpanit 1995; W.F. Laurance 1999), and constitute 33% of the existing tropical forests in the world (Whitmore 1997). Owing to their proximity to human habitation, seasonal forests also suffer a similar fate as lowland rain forests. In fact, seasonal forests are often grouped, for convenience, with rain forests, and are thus included in some of the regional deforestation calculations (e.g. Achard et al. 2002). Indeed, it is estimated that seasonal forests are being lost at the highest rate of any forest type (Figure 1.9) (Whitmore 1997). In some regions, such as Central America and Madagascar, more than 96% of these forests have already been destroyed (Krammer 1997; A. P. Smith 1997; W.F. Laurance 1999).

Table 1.1 Summary information on forests in tropical countries that have lost most of their original forests, showing land area, original and current natural forest area and change in forest area. Data derived from the United Nations Food and Agriculture Organization (FAO), United Nations Environment Programme, World Conservation Monitoring Centre (WCMC) and World Resources Institute (WRI). Countries are arranged (alphabetically) according to positive or negative annual percentage change in forest area (‘total forest’).

Figure 1.7 Deforestation rates and remaining forest area for countries with a clearing rate of greater than 0.4% per year. Country codes: BO, Bolivia; BR, Brazil; CN, People’s Republic of China; ID, Indonesia; MG, Madagascar; PY, Paraguay. (Data derived from M.C. Hansen and DeFries 2004.)

Figure 1.8 Percentage occurrence of different forest types across different regions. (Data derived from Whitmore 1997.)

Figure 1.9 Average annual deforestation rates of different forest types at regional (a) and global scales (b), with lowland seasonal forests being lost at the highest rate globally. (Data derived from Whitmore 1997.)

1.1.2 Mangrove loss

Mangrove forests (growing in saline coastal environments) represent another unique tropical ecosystem. Mangroves are juxtaposed between land and sea and found within 25° north and south of the equator, covering approximately 8% of the world’s coastline in 112 countries (Figures 1.10 and 1.11) (Adeel and Pomeroy 2002). In addition to direct overharvesting of trees, mangroves face threats from pollution, siltation, coastal development, aquaculture development and boating and shipping (Adeel and Pomeroy 2002). Traditionally, mangroves have been undervalued and largely considered to be useless swamps or wasteland (Liow 2000; Adeel and Pomeroy 2002). However, as with other forest types, mangroves support extensive biodiversity and contribute to varied ecosystem functions. For example, the presence of mangroves may enhance fish, shrimp and prawn catches (Baran and Hambrey 1998), producing an estimated US$66 to almost US$3000 of fisheries-related annual income from 1 ha of mangrove (Baran and Hambrey 1998). Although this estimate may be inflated because it does not include fisheries yield exclusively reliant on mangroves, it does show that human livelihoods can depend on this habitat type. Because of these indirect benefits to human well-being, conversion of mangroves for aquaculture may generate around 70% less revenue from the overall system than the pristine state (Balmford et al. 2002). Despite their environmental and economic benefits, mangroves are currently being lost at a rate of 2–8% per year. Between 4% and over 60% of the original mangrove cover has been lost in different tropical regions (Figure 1.12) (Valiela et al. 2001; Adeel and Pomeroy 2002).

Figure 1.10 A tropical mangrove swamp in Singapore. (Photo by Hugh Tan.)

Figure 1.11 Global distribution of mangroves (black) and tropical savannas and grassland (dark grey). [After United Nations Environment Programme – World Conservation Monitoring Centre (UNEP-WCMC) online 2007. With permission.]

In Southeast Asia, Singapore epitomizes mangrove destruction and conversion: mangrove forest cover amounted to 6334 ha (63% of original) in 1953, but by 1993 this had declined to only 6.5% (Hilton and Manning 1995), with a further reduction to 4% projected by 2030 (Figure 1.13). The primary driver of this massive destruction of mangrove forests in Singapore has been coastal development associated with urban expansion and industrialization (Hilton and Manning 1995). The mangrove loss in Singapore has also resulted in biotic losses. For example, at least four mangrove plant species (e.g. Barringtonia conoidea) have been extirpated from the island (Liow 2000). On a positive note, mangrove cover in the Central American nation of Costa Rica increased by 6% between 1983 and 1990 as a result of regeneration and plantations (Adeel and Pomeroy 2002).

Figure 1.12 Percentage of original mangrove forest loss in different regions. Error bars represent standard error and are missing from Oceania because it is represented only by Papua New Guinea. (Data derived from Adeel and Pomeroy 2002.)

Figure 1.13 Decrease in area of mangrove forest in Singapore, with projected estimates up to 2030. (After Hilton and Manning 1995. Copyright, Cambridge University Press.)

1.1.3 Loss of tropical savannas

Tropical savannas or grasslands are associated with a highly seasonal climate of a prolonged dry and a shorter wet season (Figures 1.11 and 1.14). This type of extreme climate is expected to produce some form of forest or woodland, but soil conditions (e.g. low soil fertility) or disturbance prevent the establishment of dominant tree cover in these areas. Indeed, savannas are shaped (and now managed) by fire and grazing pressures of mega-herbivores. The African savannas are the best known, covering much of central and southern Africa. However, savannas also cover large areas of Central and South America (pampas), western India and northern Australia (Figure 1.11). Savannas are characterized by continuous cover of perennial (a plant persisting for several years) grasses, often reaching 3 m at maturity. Savannas may have an open canopy of drought-, fire- or browse-resistant trees. The dominant layer of these trees distinguishes the type of savanna, for example acacia savanna and pine savanna. Both tree and grass species in savannas have underground root systems that allow them to survive prolonged periods of drought and/or fire. There are other adaptations to resist the stress imposed by droughts, e.g. baobab trees (Adansonia digitata;Figure 1.15) in Africa have evolved huge trunks to draw out and store moisture during drought, perennial grasses die back and trees lose their leaves to reduce water loss through transpiration during dry seasons.

The world’s greatest diversity (> 40 species) of ungulates (hoofed mammals) is found in the savannas of Africa and includes wildebeest (Connochaetes taurinus), oryx (Oryx gazella) and zebra (Equus spp.). These species-rich communities of large-bodied mammals attract a diverse set of carnivores such as lions (Panthera leo), cheetahs (Acinonyx jubatus), jackals (Canis adustus) and hyenas (Crocuta crocuta). Termites are also abundant in tropical savannas; they feed on decomposing animal and plant remains and thus are important for maintaining soil fertility. In fact, trees growing nearer to termite mounds in western Zimbabwe have higher nutrients and are preferred as browse by elephants (Loxodonta africana) (Holdo and McDowell 2004). Additionally, termite nesting mounds provide shelter for other animals and food for anteaters (Myrmecophaga spp.) and pangolins (Manis spp.).

Figure 1.14 A tropical savanna in Kenya. (Photo by Chuck Bargeron, University of Georgia, www.forestryimages.org.)

Figure 1.15 Baobab trees (Adansonia digitata) in Kenya. [Photo by Robert L. Anderson, United States Department of Agriculture (USDA) Forest Service, forestryimages.org.]

The Cerrado region of Brazil exemplifies the importance of, and threats to, the savannas. These savannas cover 21% of Brazil and are exceptionally rich in endemic species (Figure 1.16) (Klink and Machado 2005). Despite this richness, 55% of the 2 million km2 of forest cover in the Cerrado has been transformed or cleared for human use, with the main threats being soil erosion, uncontrolled fire and the spread of exotic grasses (Klink and Machado 2005). An issue of particular conservation concern is that 20% of threatened endemic species do not occur in any of the region’s protected areas (Klink and Machado 2005). A similar predicament is unfolding in the savannas of the Serengeti National Park in Tanzania (Sinclair et al. 2002). Some 5% of the grasslands in this region are each year converted for human use, such as agriculture. Compared with native savannas, only 28% of all bird species, and 50% of insectivorous and granivorous species, are found in agricultural areas (Sinclair et al. 2002). That study suggested that continuing human encroachment in this ecosystem would negatively affect bird species and perhaps some larger vertebrate species, such as lions and cheetahs. Worldwide, 50% of the tropical and subtropical savannas have already been sequestered for use by humans, with further projected losses of about 20% by the year 2050 (Figure 1.17) (Millennium Ecosystem Assessment 2005).

1.1.4 Loss of limestone karsts

Limestone karsts are sedimentary rock outcrops composed primarily of calcium carbonate (Figure 1.18). They were formed millions of years ago by calcium-secreting marine organisms (e.g. corals) and were subsequently lifted above the sea level by tectonic movements. The complex terrain of karsts translates into high species diversity because many of the species can be site-endemic owing to a high degree of isolation among the karsts. For example, 21% of 1216 karst-associated plant species are endemic to Peninsular Malaysia, with 11% of these being site endemics (Chin 1977). Similarly, 80% of Malaysian landsnails live on karsts, with many of them occurring only on individual karsts (Clements et al. 2006). Karsts should have high conservation priority because they are home to 143 globally threatened species, and 18 karst-dominated species have already been lost from Peninsular Malaysia due to habitat loss (Kiew 1991; Clements et al. 2006). In addition, karsts are valuable to humanity because of their rainwater storage abilities and thus play a role in maintaining the hydrological integrity of catchments. They also are magnets for tourists – karsts in Sarawak (Malaysia) generate at least US$80 000 annually in tourism-related revenues. Despite this, tropical karsts are currently being quarried heavily for limestone to be used in over 100 commercial products such as cement. More than 400 million tonnes of limestone were quarried from karsts in the tropics over a period of 5 years (Figure 1.18). Clearly, there is a need for more conservation attention to this imperilled ecosystem.

Figure 1.16 Number of species with per cent endemism and proportion of estimated species richness in the savannas of Brazil. (Data derived from Klink and Machado 2005.)

Figure 1.17 Loss of savannas over the past century and projected conversion by 2050. Bars represent medium certainty, and the error bar represents a range of values from four different Millennium Ecosystem Assessment scenarios. (After Millennium Ecosystem Assessment 2005. With permission.)

In addition to loss, fragmentation and degradation of once pristine areas, tropical habitats are affected by drivers such as climate change, invasive species, overexploitation (e.g. hunting) and pollution (Figure 1.19; Millennium Ecosystem Assessment 2005). These elements will be covered in later sections and chapters.

Figure 1.18 (a) Pristine tower karsts in Sarawak, East Malaysia, and (b) the mean (± standard error) annual limestone quarrying rates of four major tropical areas (1999–2003). (After Clements et al. 2006, Copyright, American Institute of Biological Sciences. Photo by Reuben Clements.)

1.2 Drivers of habitat loss

Direct causes of deforestation (and loss of other habitats) are multifarious, and include slash-and-burn clearing associated with swidden agriculture, selective logging, cattle ranching, plantations, permanent agriculture, fuel wood collection and transmigration. These drivers can act individually or in concert. In the tropics, the main proximate drivers of deforestation are agriculture, followed by timber extraction and infrastructure (urban) expansion (Geist and Lambin 2002). However, the precise causes of deforestation are underpinned by complex and geographically variable factors. For instance, some governments have little choice but to sell forests as logging concessions to alleviate foreign debt (Bawa and Dayanandan 1997). Below we discuss in some detail the various drivers of habitat loss in the tropics.

1.2.1 Human population pressure

The increasing demand for, and consumption of, natural resources by humans show no sign of abating. Rapid economic development, population expansion and poverty are key drivers of land conversion (Giri et al. 2003; Jha and Bawa 2006). Demographic growth is particularly steep in tropical countries, where the size of the human population has increased by 3.1 billion between 1950 and 2000, and is projected to grow by another 2 billion before 2030 (United Nations 2004). Within the next 100 years, as many as 11 billion people may inhabit the planet, a number that will be difficult to sustain (Palmer et al. 2004). Urbanization will greatly expand in the future, with expectations that more than half of the world’s total human population will be living in cities by 2030 (see Figure 1.6) (Palmer et al. 2004). Expanding human populations, and their specific actions (e.g. land conversion), exert substantial pressure on natural resources and native biodiversity (Cardillo et al. 2004). Poor policy choices can also exacerbate environmental destruction (Jha and Bawa 2006).

Figure 1.19 Factors that affect tropical habitats and their current trends. (After Millennium Ecosystem Assessment 2005. With permission.)

It would be immeasurably informative, from both a scientific and management perspective, if we could hypothetically excise a representative tropical country, allow it to fulfil its economic potential, and document the consequent loss of natural habitats and biodiversity, all within a greatly accelerated time frame. It is both depressing and fortunate that the Southeast Asian island nation of Singapore provides exactly such an ecological worst-case scenario for the tropics. Singapore has experienced an exponential population growth from around 150 subsistence-economy villagers around 1819 to 4 million people in 2001 (Corlett 1992; World Bank 2003). In particular, within the past few decades, Singapore has transformed itself from a Third World country of squatters and slums to a developed metropolis of economic prosperity and thus has been widely regarded, by the regional developing countries, as the ideal economic model. However, the success of Singapore came at a hefty price, one that was unfortunately paid for most particularly with its biodiversity (Brook et al. 2003a). The island has suffered massive deforestation, initially from the cultivation of short-term cash crops (e.g. gambier: Uncaria gambir, rubber), and subsequently from urbanization and industrialization (Corlett 1992). With this destruction of habitats (rain forest, swamp forest and mangroves) has come the extirpation of at least a third of the island’s known biodiversity. Similar environmental scenarios are now unfolding in other tropical countries, often at much greater geographic scales (Jepson et al. 2001).

As the human population of tropical countries continues to grow, enormous pressures will be placed on their natural resources (World Bank 2003). The current trend in the tropics suggests that forest loss will likely increase in tandem with human population density, and in some cases due to economic expansion as well (Figure 1.20 for all tropical countries). The point to note, however, is that the pressure of dense human populations represents only one of the factors in habitat loss because, even in areas with relatively few human residents in the tropics, there can be widespread loss of natural forests (Whitmore 1997).

A burgeoning human population, even with an increasing concentration of people in urban areas, means more mouths to feed, and agriculture is the main factor in land conversion in the tropics (Figure 1.21), with its estimated contribution to annual tropical forest losses being as high as 90% (Hardter et al. 1997; Achard et al. 2002). In Asia, 100 million ha of land was converted to cropland between 1880 and 1980. Over these 100 years, the area of land converted to agriculture expanded by 86% in this region (Flint 1994; Richards and Flint 1994), largely at the expense of its forests (Flint 1994; Bawa and Dayanandan 1997) (Figure 1.22). Production of soya bean (Glycine max) has increased 100-fold since 1961 in Argentina and Brazil, largely for export to China (Donald 2004). This has resulted in a severe shrinking of Cerrado grasslands (Donald 2004).

Figure 1.20 Socioeconomic correlates of percentage forest loss. The proportion of forest area remaining in tropical countries did not correlate with (a) gross national income (GNI) but correlated negatively with (b) population density. Percentage of forest area remaining is defined as the proportion of current total forest area over estimated forest cover about 8000 years ago assuming current climatic conditions. PPP, purchasing power parity. (Data derived from www.earthtrends.wri.org.)

Globally, over the last three decades, agricultural areas have doubled from 50 million ha to 100 million ha (Niesten et al. 2004), and now cover a quarter of earth’s land surface (Millennium Ecosystem Assessment 2005). By 2030, it is predicted that an additional 120 million ha of agricultural land will be needed by developing countries to support their increased populations (M. Jenkins 2003); therefore, land clearing for agriculture is almost certain to continue at a rapid pace. In addition, in many areas of the tropics, factors such as low soil fertility and high levels of erosion mean that land conditions are not particularly conducive to sustainable agriculture, thus promoting a cycle of forest destruction. Farmers have to burn forest vegetation to release nutrients that enhance soil fertility and, as a result of the region’s characteristically high rainfall, these nutrients are usually washed away rapidly, making the soil less fertile; in as little as 3 years, the ground is no longer capable of supporting crops (Härdter et al. 1997). Farmers are then forced, because of the reduced soil fertility, to look for new forested areas to clear and burn.

Figure 1.21 Agriculture in the tropics. (Photo by Cagan Sekercioglu, naturalphotos.com.)

Figure 1.22 Change in cultivated area and forest cover of South and Southeast Asian countries (filled symbols: forest cover; unfilled symbols: cultivated areas). (After Flint 1994. Copyright, Elsevier.)

Agricultural plantations (large-scale, export-oriented monocropping) are also on the rise in the tropics. Areas under plantation doubled from 4% to 8% between the 1970s and 1984 (Hartemink 2005) – a trend that has most likely continued since. For instance, the area under oil palm (Elaeis guineenis) cultivation increased from 150 000 ha in the 1970s to over 3 million ha in 1998 (Hartemink 2005). Similar trends have been found for cocoa plantations in the Ivory Coast and for sugar cane (Saccharum officinarum) plantations in India and Brazil. In Brazil, soya bean (Glycine spp.) cultivation has increased by 13 million ha in the past 30 years, mostly at the expense of its wooded savannas (Niesten et al. 2004); these agricultural plantations contribute substantially to the gross national product (GNP). Forest conversion to cropland in the Brazilian Amazon is directly correlated with soya bean prices, indicating that high crop prices in the international market can promote deforestation (D.C. Morton et al. 2006). In the 1980s, exports from plantations contributed 22% to the GNP of the Ivory Coast, and rubber accounted for 10% of GNP exports in Malaysia (Hartemink 2005). However, these plantations can release pollutants, cause soil erosion and declining soil fertility and can be poor in sequestering carbon and promoting biodiversity values (Hartemink 2005).

Cultivation of coca and poppies for the illicit drug trade may be the cause of almost half of the deforestation in neotropical countries (Aldhous 2006). Biologists and governmental officials trying to prevent deforestation as a result of illicit drug demand (mostly in the USA) are threatened with violence (Aldhous 2006).

Massive resettlement programmes, such as those in Indonesia, Thailand, the Philippines, Burundi and Rwanda, also facilitate deforestation (R.L. Bryant et al. 1993; www.fao.org). Fuel wood is thought to constitute 85% of total energy consumption in West Africa, and this has resulted in heavy deforestation and occasional shortages of such wood, particularly in Niger, Nigeria and Togo (www.fao.org). Civil war in tropical countries has compromised conservation because illegal logging money has been used to fund conflict (Talbott and Brown 1998; Draulans and van Krunkelsven 2002), although war can sometimes facilitate forest regeneration, for instance by deterring commercial operations (Hecht et al. 2006). Last, but not least, the liberal granting of forestry concessions, largely though cronyism and corruption, does not bode well for the remaining tropical forests (Geist and Lambin 2002; see Chapter 10).

1.2.2 Perverse subsidies

Some government actions inadvertently promote poor land use practices. Subsidies designed to promote agricultural production also facilitate land clearing (Barbier 1993; A.N. James et al. 1999). These subsidies are called ‘perverse’ because, over the long term, they adversely affect the economy and the environment (Myers 1998). For example, worldwide, citizens pay US$950–1450 billion annually to subsidise fisheries and the timber and oil palm industries (Myers 1998; van Beers and de Moor 1999). The largest amount of money (US$345 billion/year) goes to agriculture and fisheries (van Beers and van den Bergh 2001). Global ocean fisheries cost US$100 billion a year, of which only US$80 billion is recovered through sales – the shortfall is made up by government subsidies (Myers 1998). This has resulted in the depletion of fisheries stocks to unsustainable levels, bankruptcy of fishing businesses and a high unemployment rate in fisheries communities. Despite this problem, the European Union (EU) has been increasing subsidies to its fishing fleets in West Africa, thus artificially inflating profitability against the backdrop of declining fishing stocks (Brashares et al. 2004). In Brazil, the depletion of soils, forests and fisheries as a result of perverse subsidies to agriculture has depressed its economic growth potential by up to 30% (Myers 1998).

Coffee cultivation provides a useful illustration of the nature of perverse subsidies in agriculture. During the 1990s, Asian governments with the support of the International Development Bank promoted intensive coffee cultivation in countries such as Indonesia and Vietnam, hence elevating Indonesia to the world’s fourth largest coffee exporter and the second largest producer of coffee after Vietnam. Unfortunately, this short-term economic gain resulted in massive forest conversion, and eventually proved to be economically unsustainable due to overproduction and the subsequent collapse of world prices (O’Brien and Kinnaird 2003). Despite it being clear that coffee production is not economically attractive in many situations and is detrimental to biodiversity, the Indonesian government plans to expand coffee production further. O’Brien and Kinnaird (2003) recommended that the adoption of coffee cultivation be strongly discouraged in protected areas and that strident attempts should be made to curtail deforestation for this type of cultivation. Certainly, organizations such as the International Coffee Organization need to play a bigger role in promoting a balance between coffee production and biodiversity needs.

In addition to agriculture, governmental financing of road construction can act as an indirect subsidy by facilitating logging (Flint 1994; van Beers and van den Bergh 2001) and can lead to an increase in the hunting of wild animals by providing easier access to the forests (see Chapter 6). Further, underpricing of timber and subsidies of private harvesting (e.g. low logging fees and taxes) promote deforestation (Barbier 1993). For example, in the Philippines, timber revenues collected by the government during the late 1980s were six times lower than the prevailing market value (US$39 versus US$250 million; Barbier 1993). More than 46% of the money generated by timber concessions in Malaysia and Indonesia since the early 1990s remains uncollected (www.fao.org), suggesting that logging does not benefit the local people economically.

1.2.3 Commercial logging

Commercial logging is also another common direct driver of deforestation, especially in the tropics (Geist and Lambin 2002). Trees are felled for sale as timber, timber products (e.g. woodchips), or pulp. Between 1981 and 1990, 5.6 million ha of tropical forest was logged for timber (Whitmore 1997). Such logging activities predominantly occur in the primary forests (Figure 1.23; Whitmore 1997). Forestry industries account for 3% of the world’s gross economic output, or approximately US$330 billion annually (Sizer and Plouvier 2000). The annual total worldwide consumption of wood is around 3 billion cubic metres, with about half of that consumed as firewood. The Asia-Pacific region now drives log exports in the tropics, encompassing 67% of the total volume (Sizer and Plouvier 2000; Figure 1.24).

Over the past few decades, Indonesia, Brazil and Malaysia have logged more than half of the world’s commercially viable tropical timber, with Thailand and India also in the top five producers [ITTO (International Tropical Timber Organization) 2003; Figure 1.25]. The high level of commercial logging is also of concern in countries with currently vast intact tropical forests, such as Gabon, Cameroon and Papua New Guinea (Figure 1.26), as there is little possibility of further protection of forests in these countries. In many of these countries, timber harvesting occurs in the absence of any management plan that might seek sustainability [Centre for International Forestry Research (CIFOR) 2004].

Figure 1.23 Proportion of remaining natural forest areas and percentage of primary forests area logged for the first time in those forests. (Data derived from Whitmore 1997.)

Figure 1.24 Log exports of round wood from different regions from 1996 to 1998. (Data derived from Sizer and Plouvier 2000.)

Japan, South Korea and the People’s Republic of China are the main importers of tropical timber products (Sizer and Plouvier 2000). Forest products exported by developing countries are usually subject to low export duties, particularly on unprocessed logs (Barbier 1993). Trade liberation, through the removal of export restrictions, may increase log exports (up to fourfold in the Philippines) and thus cause a further acceleration in deforestation (Barbier 1993). In addition, current bans on commercial logging within India and the People’s Republic of China promote higher demand for the supply of tropical wood from other countries (www.birdlife.net). Between 1997 and 2002, China’s forest product imports soared by 75%, from US$6 to 11 billion (Sun et al. 2004). Over 70% of China’s forest products are supplied by countries in the Asia-Pacific region (Katsigris et al. 2004). Many supplying countries are rife with unsustainable harvesting, illegal logging and concomitant negative impacts on human livelihoods. Greater attention by governments, market leaders and international organizations is needed to address the problems that tropical timber export creates in the source countries (Katsigris et al. 2004).

Figure 1.25 Tropical timber producers from 1999 to 2003. (Data derived from International Tropical Timber Organisation 2003.)

Figure 1.26 Production of various commercial logging materials from the top nine countries and their remaining natural forest area. (Data derived from Sizer and Plouvier 2000.)

Moreover, deforestation is actually encouraged by governments in the tropics because of high international demand for tropical wood and wood products (Kummer and Turner 1994), and examples of sustainable natural forest use in the tropics are difficult to find (Bowles et al. 1998; Putz et al. 2000; W.F. Laurance et al. 2001a). Unsustainable logging remains 20–450% more profitable, at least over the short term, than sustainable practices such as fruit collection and meat production (Bowles et al. 1998; but see Balmford et al. 2002). Logging in many tropical countries is still done by clear-felling (Barbier 1993), yet even ‘selective logging’ can be very wasteful, resulting in the felling of an average of 25 non-commercial trees for every commercial-quality tree extracted (Myers 1991) and 40–50% of the canopy cover being destroyed (Cochrane 2003). Further, logging concessions are typically awarded for short durations (5–25 years) that tend to promote logging in new areas (Barbier 1993).

Old-growth forests are also being targeted and depleted across the tropics (Whitmore 1997). The highest percentage of logging in neotropical old-growth forests occurred from 1981 to 1990 (see Figure 1.23; Whitmore 1997), and in many areas of Southeast Asia old-growth forests are being logged to oblivion (Barbier 1993; Whitmore 1997). Clearly, stiffer guidelines are needed to regulate, and perhaps curtail, mass tropical timber production and export. These might include mandatory timber certifications, better economic incentives to encourage sustainable harvesting, substantial reviews of export duties and laws and a more widespread promotion and education of environmental issues (see Chapter 10). Furthermore, because they are often the only institutions in remote areas, logging companies can themselves assist in environmental protection, although there are instances of officials wanting to stop illegal logging being intimidated by arson, attempts at bribery and murder (Jepson et al. 2001; Aldhous 2006).

Agriculture and commercial logging may have differing impacts on deforestation rates in the tropics; however, in many areas, both logging and agriculture act in concert to exacerbate deforestation (Kummer and Turner 1994). As described earlier, by creating roads, logging operations enhance physical access to forests. This greater access increases the likelihood of invasion by humans (e.g. hunters, farmers and miners) and exotic organisms associated with humans (e.g. rats, dogs, cats), and is a cause of considerable concern for the long-term prospects of tropical biodiversity (W.F. Laurance et al. 2001a).

1.2.4 Weak governance

Anaemic national institutions and poor enforcement of legislation remain a major hindrance to curtailing tropical deforestation (W.F. Laurance 1999). Liberal granting of forest concessions, non-existent or poor forestry practices, weak governance structures and political corruption all work to maintain high deforestation rates in developing countries (R.L. Bryant et al. 1993; Geist and Lambin 2002; R. J. Smith et al. 2003). Illegal logging (timber harvesting, transportation and trade in violation of national laws) and encroachment into nature reserves remain a problem across the tropics (www.fao.org/forestry; T. Whitten et al. 2001; DeFries et al. 2005). For example, it is reported that illegal and possibly unsustainable logging remains rampant in Indonesia with the implicit backing of politicians, businesses and the military (Kinnaird and O’Brien 2001; T. Whitten et al. 2001; Stibig and Malingreau 2003; see Chapter 10). Certain people implicated in illegal logging continue to retain prominent political positions (T. Whitten et al. 2001). Forest policies are not sufficiently well developed to protect the remaining forests adequately and to stem the growth of industries based on forest exploitation. For instance, Indonesia’s paper and pulp industry has grown sevenfold since the 1980s, with a similar expansion in the production of plywood. Further, the oil palm plantation areas and resettlement plans for some native people have placed even greater pressure on these forests (Stibig and Malingreau 2003).

Sadly, the events occurring in Indonesia are not anomalous – they in fact epitomize disturbing actions across most of the tropics. Illegal logging costs the timber industry up to US$15 billion annually (S. Johnson 2003). Seneca Creek Associates and Wood Resources International (2004) estimate that up to 10% of forestry trade worldwide is based on illicit timber products. This rampant illegal activity in the tropics makes up between 20% and 90% of forest production and trade in some tropical countries (Figure 1.27; Seneca Creek Associates and Wood Resources International 2004), with corruption seeming to facilitate logging (Figure 1.28). The construction of roads in many tropical areas further enables illegal logging (Barbier 1993).

In many tropical nations, forests are managed by government departments, whose main interest seems to be to increase commercial logging and the export of timber products without any consideration for the conservation of biodiversity (Byron and Waugh 1988). Furthermore, these departments remain understaffed and heavily politically influenced (Barbier 1993), so that logging companies identified as having poor environmental practices (e.g. promoting forest fires) can continue to conduct unscrutinized ‘business as usual’ (T. Whitten et al. 2001). Rampant corruption and illegal activities hinder proper management of forests in many parts of the tropics (Kummer and Turner 1994; see Chapter 10). For example, corruption has been a major contributing factor to the heavy deforestation of the Philippines (Kummer and Turner 1994), and this is very likely to be also a major factor in furthering deforestation in other tropical countries. The few but well-publicized struggles by some native groups (e.g. Penan of Sarawak) to halt logging have generally been in vain (R.L. Bryant et al. 1993).

Figure 1.27 Proportion of illegal production of wood products and/or imports of different countries across various tropical regions. (Data derived from Seneca Creek Associates and Wood Resources International 2004.)

Figure 1.28 Relationship of estimates of suspicious log supply and the corruption index of selected countries. Size of bubbles represents volume of suspect roundwood, including imports. (After Seneca Creek Associates and Wood Resources International 2004. With permission.)

1.3 Biodiversity hotspots

Because there are finite economic and logistical resources available for conservation, wisdom dictates that their value in retaining biodiversity must be maximized. Therefore, it is critical to identify priority areas where conservation needs are the greatest, in order to achieve the most significant payoffs in terms of the global preservation of species and communities. On this basis, Myers (1988) identified 10 terrestrial ‘hotspots’ where levels of vascular plant endemism were exceptional but which were marred by massive habitat loss and thus should be accorded the highest conservation priority. To these, Myers later added another eight hotspots – these 18 hotspots support 20% of the earth’s plant species within just 0.5% of its land surface (Myers 1990).

Critics of the hotspots approach to identifying conservation priorities have argued that there are poor complementarities among taxonomic groups, e.g. hotspots for plants may not be hotspots for butterflies (Reid 1998). In 2000, Myers et al. (see Spotlight 1: Norman Myers) expanded this paradigm of conservation planning by including, in addition to vascular plants, key vertebrate groups (amphibians, reptiles, birds and mammals) in their analyses. Vascular plants and vertebrate groups were the best candidates for such analyses because the available data on the distribution and conservation status were sufficient to make robust assessments. Myers et al.’s (2000) now famous analyses identified 25 terrestrial biodiversity hotspots globally – defined as regions that harbour a high diversity of endemic species from plant and animal taxa and, simultaneously, have been heavily impacted and altered by human activities. The criteria for designating a hotspot were that, out of the 300 000 known vascular plant species in the world, at least 0.5% or 1500 vascular plant species should be endemic to it, and that it should have lost at least 70% of its primary vegetation (habitats rich in endemic species). Collectively, these 25 biodiversity hotspots have exceptionally high endemism and harbour some 44% of world’s plant species and 35% of its vertebrate species. These hotspot areas collectively have lost 88% of their primary vegetation, thus restricting these endemic species to only 1.4% of the earth’s land surface. Sixteen (64%) of these hotspots are in the tropics. The five ‘hottest’ hotspots (highest levels of endemicity coupled with the greatest threats) are all in the tropics – the tropical Andes, Sundaland, Madagascar, Brazil’s Atlantic Forest and the Caribbean. These five together contain 20% of all vascular plant and 16% of vertebrate species, yet cover a mere 0.4% of the earth’s land surface.

Myers et al. (2000) argued that conservation in these 25 biodiversity hotspots is imperative if we are to counteract the mass extinction crisis that is now unfolding (see Chapter 9). The threat to biodiversity hotspots from humans is imminent – 20% of 1.1 billion people inhabit these areas (Cincotta et al. 2000). More worryingly, between 1995 and 2000, the human population expanded by 1.8% annually in these hotspots, which is a much higher rate than the average annual expansion for the whole world of 1.3% (Cincotta et al. 2000). This trend suggests that, in these hotspots, human-induced environmental changes are likely to proceed more rapidly than in other parts of the world (Cincotta et al. 2000; Shi et al. 2005). Conservation intervention is, therefore, absolutely necessary in these areas. Myers et al. (2000) calculated that, on average, US$20 million per year is needed to safeguard each hotspot – which amounts to a total of about US$500 million annually – a value many orders of magnitude lower than the US$1.4 trillion that global citizens spend in subsidies to degrade environments and economies alike (Myers 1999).

Spotlight 1: Norman Myers

Biography