Conservation Scholars: Daniel Simberloff

30 10 2008

This series on ConservationBytes.com takes a page out of our book Tropical Conservation Biology (Sodhi, Brook & Bradshaw) – therein we produced a series of ‘Spotlights’ describing the contributions of great thinkers to conservation science. Each highlight of a Conservation Scholar includes a small biography, a list of major scientific publications and a Q & A on the person’s particular area of expertise.

Our fifth Conservation Scholar is Daniel Simberloff…

Biography

As a child in rural Pennsylvania, I was fascinated by nature, collecting insects from age five and keeping insects, turtles, and fish as pets. This idyll crashed to a halt at age 11 when we moved to an industrial suburb of New York City. I attended Harvard College, where I became excited by maths and majored in it. My junior year, while enjoying a non-majors biology course and realising that I wasn’t so enthusiastic about a maths career, I consulted a biology department advisor about postgraduate work. Frank Carpenter, an insect palaeontologist, astounded me by saying I could go to graduate school in biology with a little coursework in my final year. He also directed me to Ed Wilson as a potential graduate advisor. Ed introduced me to ecology and argued that maths is crucial to the maturation of ecology. He taught me an enormous amount of biology and encouraged me in a great doctoral dissertation project, testing the theory of island biogeography that he had recently propounded with Robert MacArthur. We collaborated in fumigating small Florida mangrove islands and studying their recolonisation by insects. Bill Bossert taught me about computers well before everyone knew about them. Beginning with my doctorate, my main interest has been how different species fit (or do not fit) together in communities, and this interest led to research in conservation issues, most notably on refuge design and impacts and management of introduced species, as well as more academic aspects of ecology, like the role of inter-specific competition. As a faculty member at Florida State University and now the University of Tennessee, I have learnt an enormous amount from excellent colleagues, postgraduate students, and post-doctoral fellows. I also quickly interacted with policy makers and non-governmental organisations on conservation issues, first at the local and state levels, then nationally. My most important advice to prospective conservation biology students is to interact with challenging people doing interesting research and to engage in local conservation issues.

Major Publications

Questions and Answers

1. What are the defining characteristics of an alien organism that make it ‘invasive’?

An invasive introduced species is one that spreads into more or less natural ecosystems and thrives there, affecting native species.

2. Is there merit in the idea that tropical ecosystems are more resistant to invasion due to their species richness and complexity?

I don’t believe either premise, that tropical ecosystems are particularly resistant to invasion or that complex ecosystems with many species are particularly resistant to invasion. There are many invasions into tropical ecosystems, including species-rich ones, and extensive research fails to support Elton’s hypothesis that biological invasions are greatly facilitated by low native species richness. Any ecosystem is invasible by the right invader.

3. How common are ‘invasional meltdowns’, and what are the best tropical examples?

It is too early to know just how common invasional meltdowns are, but every year more cases are suggested, and some are buttressed by careful study. An important tropical example is the near destruction of the forest ecosystems of Christmas Island (Indian Ocean) by the introduced yellow crazy ant, whose population explosion was facilitated by later invasions of scale insects that produced a honeydew fed on by the ants. The ants devastated populations of the keystone species, the famed red land crab, and their impact on the forest was exacerbated by a plant pathogen (a sooty mould). See O’Dowd D. J., Green P. T. & Lake P. S. (2003). Invasional ‘meltdown’ on an oceanic island. Ecology Letters 6, 812-817.

4. Biological, chemical, mechanical, genetic or ecosystem control: any to recommend?

The best defence against invasive introduced species is to avoid introducing them in the first place, by having more stringent regulations on movement of goods and by better inspections of luggage and cargo. The second line of defence is an effective early warning/rapid response system, which requires both ongoing monitoring and the institutional and legal mechanisms to act quickly when an invasion is discovered. Many introduced species have been eradicated before they spread too far, and many more could have been eradicated if a good early warning/rapid response system was in place. Once a species is established, biological, chemical, and mechanical control, genetic intervention, and ecosystem management all have roles to play in particular cases in maintaining invader populations at low levels. However, ecosystem management and genetic intervention, though widely discussed, have so far rarely been used to deal with introduced species, particularly in natural environments. By contrast, there are many successful uses of biological, chemical, and mechanical control. It is nonetheless important to recognize that the great majority of biological control projects do not control the target pest, that species introduced for biological control can and sometimes do attack non-target native species, and that once a biological control agent is well-established, it is difficult if not impossible to eradicate it, even if it turns out to be problematic. The latter feature contrasts with mechanical and chemical control, which can simply be terminated if they are not working as planned. For this reason, I feel it is important to consider all possible means of dealing with introduced pests, and to take account of the irreversibility and historically low success rate of biological control.

5. Do large-scale, co-ordinated efforts like the United Nations Global Invasive Species Program (GISP) offer the best means of addressing the problems of alien species?

Large international efforts, such as GISP, are important tools in dealing with introduced species. They can particularly aid in slowing down the rate at which non-native species arrive and in publicizing the problem and educating people about how to deal with particular invasions (as GISP has done). However, the most important response to introduced species will always be the efforts that each nation will mount against invaders that breach its borders, in terms of early warning/rapid response, attempted eradication, and effective maintenance management.

CJA Bradshaw

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(with thanks to Navjot Sodhi, Barry Brook, Ward Cooper, Wiley-Blackwell and Daniel Simberloff for permission to reproduce the text – buy your copy of Tropical Conservation Biology here)


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Categories : alien species, conservation, conservation biology, conservation scholars, ecosystem, extinction, impact, invasive species, island biogeography, recovery, threatened species

Classics: Invasion Meltdown

26 10 2008

One for the Classics page…

Daniel Simberloff is probably best known for his work on the implications of invasive (non-indigenous) species for biodiversity, although he has contributed to a wide range of conservation disciplines.

© E. Lecouturier

© E. Lecouturier

A seminal paper that he co-wrote with Betsy Von Holle is one I consider to be a conservation Classic: their 1999 paper in the inaugural issue of Biological Invasions entitled Positive interactions of nonindigenous species: Invasional meltdown?

The establishment of non-indigenous species can have severe negative impacts on ecosystems. Introduced species that become invasive (widespread and locally dominant) transform habitats, degrade ecosystem services, reduce biodiversity and are some of the greatest threats to ecosystems today (perhaps nearly as important as habitat loss and over-exploitation).

The so-called ‘invasion meltdown‘ describes the process by which the negative impacts induced on native ecosystems by one invading non-indigenous species are exacerbated by interactions with another exotic species.

Although there isn’t a lot of information on invasion meltdowns, one good example comes from Christmas Island in tropical Australia. The introduced yellow crazy ant (Anoplolepis gracilipes) exploded in numbers when another exotic species, a scale insect, was introduced about the same time that a native scale insect species also had a local outbreak.  Because ants protect scale insects from predators and parasites in return for scale honeydew, the crazy ant suddenly had a much more abundant food source, leading to the huge increase in the ant population. This large ant population devastated the population of native red crab (Gecarcoidea natalis) and resulted in massive increase in forest undergrowth due to reduced herbivory by crabs (see O’Dowd et al. 2003). The great decline in red crabs may also make the island more vulnerable to other plant invasions.

What did Simberloff & Van Holle’s idea and subsequent examples of invasion meltdowns teach us? I believe their paper really hit home the idea that invasive species were not only a threat to biodiversity, but the self-reinforcing mutualisms of invasive species could rival other forms of human-induced biodiversity decline. Indeed, many of the effects of invasive species will be reinforced by global climate change through increasing temperatures, rising sea levels and changing rainfall patterns that increase the potential range and spread of invading species, so the problem is only going to get worse. This is why the U.N. began the Global Invasive Species Programme (GISP), and world-wide, countries are attempting to restrict the flow of invasive species so that their negative effects are lessened. Identifying the extent of the problem has stimulated a lot of people to act accordingly.

CJA Bradshaw

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Categories : alien species, biodiversity, climate change, conservation biology, disease, ecosystem, extinction, function, impact, invasive species, recovery, research, threatened species

Conservation Scholars: Mark Cochrane

22 10 2008

This series on ConservationBytes.com takes a page out of our book Tropical Conservation Biology (Sodhi, Brook & Bradshaw) – therein we produced a series of ‘Spotlights’ describing the contributions of great thinkers to conservation science. Each highlight of a Conservation Scholar includes a small biography, a list of major scientific publications and a Q & A on the person’s particular area of expertise.

Our fourth Conservation Scholar is Mark Cochrane…

Biography

I am a Professor at the Geographic Information Science Center of Excellence at South Dakota State University and am jointly appointed with the Department of Biology and Microbiology and the Department of Geography. I conduct interdisciplinary work that combines remote sensing, ecology and other fields of study to provide a landscape perspective of the dynamic processes involved in land-cover change. I first became interested in ecology through coursework while I was completing my baccalaureate in Environmental Engineering at the Massachusetts Institute of Technology. I then spent a year working on a variety of research projects in Antarctica, furthering my interest in science. Having had enough of cold-weather environments, I chose to do my postgraduate research in the Brazilian Amazon and, in 1998, received a doctoral degree in Ecology from The Pennsylvania State University. I am among the world’s leading experts on wildfire in tropical ecosystems. I am renowned for documenting wildfire characteristics, behaviour and severe effects in tropical forests, as well as how current systems of human land-use foster wildfires. My research focuses on understanding spatial patterns, interactions and synergisms between the multiple physical and biological factors that affect ecosystems. Recently published work emphasizes human dimensions of land-cover change and the potential for sustainable development. My collaborative research with the Brazilian NGO IMAZON (The Amazon Institute of Man and the Environment) has been instrumental in the Brazilian government’s recent (2003) program to expand its national forest system in the Amazon to 50 million hectares. In my ongoing research programs, I continue to investigate the drivers and effects of disturbance regime changes resulting from various forms of forest degradation, including fire, fragmentation and logging.

Major Publications

Questions and Answers

1. Are fires in tropical landscapes more frequent now than in the past?

Yes. Fires are much more prevalent in the tropics than in the past. The issues with fire in tropical landscapes do not centre on the presence of fire in these landscapes, but with the frequency with which they are burning. In many regions of the tropics, current land-use practices result in surviving forest fragments being subjected to fire so often that they are rapidly being degraded by a fire regime that they cannot withstand. Fire is the primary tool for clearing and maintaining agricultural land. Forests are slashed and allowed to dry before being burned to release their nutrients to the soils. Many lands are subsequently turned into pastures, which also are burnt frequently in order to keep trees from regrowing. Most land use is fire-dependent. Forests are also subjected to selective logging, which removes only the valuable trees and leaves the remaining forests susceptible to escaped fires. Having fire-dependent agriculture embedded in fire-susceptible forests quickly leads to forest fires. Once this occurs, the landscape is quickly converted from one of a few flammable islands (e.g., pastures) within a near fire-immune sea of vegetation (i.e., rain forests), to one where a fire at any location can permeate an entire region, forests and agricultural lands alike.

2. Will global climate change be important in altering future fire regimes?

Yes. Global climate change will likely result in important changes in regional fire regimes. Global climate models (GCMs) do not all agree on what the future climates will be like, but it is fairly certain that temperatures will increase substantially, especially in interior regions such as the upper Amazon. Most models show a concomitant increase in rainfall for these regions, but it is uncertain whether or not these increases will be enough to offset the drought stress from rising temperatures. Rainfall reductions from ongoing deforestation, however, will probably be greater than any projected increases due to global climate change, leading to a net increase in drought stress and fire behaviour, further stressing these important ecosystems.

3. How important are the adverse effects of fire on tropical biotas relative to other drivers such as habitat loss and land use change?

Fire is what integrates tropical landscapes. Habitat loss is primarily seen as a function of deforestation, but forest degradation through logging and fire causes substantial changes in forest structure and composition that affect habitability. The key aspect of wildfire is that once it has damaged a region’s forests, it effectively changes the ‘rules of the game’ for land management. What was once a highly fire-resistant ecosystem becomes a highly fire-susceptible forest. A positive feedback of increasing fire frequency, fire intensity and fire severity can become established. Instead of burning once every thousand years or more, these forests may burn once every 10 years or less. These forests cannot withstand such a fire regime and several fires can effectively deforest an area. As the landscape becomes more permeable to fire, even diligent landowners have difficulty protecting their lands from fires. Uncontrolled fires destroy large-investment, high-return perennial crops such as rubber tree, pepper and fruit plantations, making cattle ranching the most viable land use. Pasture grass is the most flammable land cover possible and only exacerbates a region’s fire problems.

4. Is there a theory in fire ecology, and if yes, what is it?

The short answer is no. To my knowledge there is no accepted theory underlying fire ecology.

CJA Bradshaw

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(with thanks to Navjot Sodhi, Barry Brook, Ward Cooper, Wiley-Blackwell and Mark Cochrane for permission to reproduce the text – buy your copy of Tropical Conservation Biology here)


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Categories : South America, climate change, conservation biology, conservation scholars, ecosystem, fire, habitat loss, research, tropical

Remove, Flog and Dump: The Story of Stuff

18 10 2008
© Tides Foundation & Funders Workgroup for Sustainable Production and Consumption

© Tides Foundation & Funders Workgroup for Sustainable Production and Consumption

Related to a recent post on the idiocy of anthropogenically induced climate change, the lunacy of our current economic system and the complete lack of valuing undervaluing of ecosystem services on which our lives depend, I invite you to watch the highly entertaining Story of Stuff. Although terribly American (well, I guess that’s excusable given it is made by an American and targets other Americans, the greatest per capita resource consumers in the world), it applies to everyone, everywhere.

From its extraction through sale, use and disposal, all the stuff in our lives affects communities at home and abroad, yet most of this is hidden from view. The Story of Stuff is a 20-minute, fast-paced, fact-filled look at the underside of our production and consumption patterns. The Story of Stuff exposes the connections between a huge number of environmental and social issues, and calls us together to create a more sustainable and just world. It’ll teach you something, it’ll make you laugh, and it just may change the way you look at all the stuff in your life forever.


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Categories : conservation, ecosystem services, environmental policy

Moving forward with extinction risk predictions from climate change

15 10 2008

A little belated, but I thought this was worth mentioning for the Potential list…

–

One from Keith and colleagues in Biology Letters entitled Predicting extinction risks under climate change: coupling stochastic population models with dynamic bioclimatic habitat models is a nice example of a way forward to predict the extremely complex array of ecological processes and patterns that may arise from rapid climate change.

One of the major problems with predicting how biodiversity might respond to climate change is the typical simplicity of single-species ‘envelope’ models – these models basically use tolerance limits (generally, physiological) or optimum conditions to predict how a species’ distribution might change. Unfortunately, this usually negates the complex dynamics of populations, the dispersal capacity of individuals, and interactions with other species that may all dominate possible responses. In other words, climatic envelope models may be way, way off (and probably vastly optimistic).

Keith and colleagues have brought us a step closer to better predictions of (and hopefully, better responses to) climate change effects on species. They linked a time series of habitat suitability models with spatially explicit stochastic population models to explore factors that influence the viability of plant species populations in South African fynbos, a global biodiversity hotspot. They discovered that complex interactions between life history, disturbance regimes and distribution patterns mediate species extinction risks under climate change.

Well done! Our next challenge is to incorporate multiple species’ interactions into such models (just to make them as mind-bogglingly complex as possible) to give us better approaches for managing our depauperate future.

CJA Bradshaw

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Categories : Africa, bioclimatic envelope, biodiversity, climate change, conservation biology, extinction, fire, niche model, population viability analysis

Loss of nature’s value makes bank crisis look ridiculous

13 10 2008

Thanks for pointing this one out, Tim (see ConsBlog.org). In the theme of demonstrating (how many different ways do we need to show this before it bloody well sinks in?) the value of ecosystem services currently being degraded by habitat loss, invasive species, over-exploitation and climate change, some people in power are starting to take notice.

All you investors, bankers, share brokers and buyers – beware! Without a large upheaval of the current economic system that promotes absolute consumption and growth in a finite and dwindling resource base, you will lose a lot more that the value of a few shares.

The global economy is losing more money from the disappearance of forests than through the current banking crisis, according to an EU-commissioned study.

It puts the annual cost of forest loss at between $2 trillion and $5 trillion… (read on)



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Categories : conservation, ecosystem services, environmental economics, environmental policy, investment

Poor media coverage promotes environmental apathy and untruths

11 10 2008

I just came across this excellent opinion piece by James Fahn on how climate change is covered by the media.

Poor countries’ media must tackle climate change

Paraphrasing briefly, the article laments the ill-equipped, uninformed and lowly stature of reporters covering climate change issues. The corollary is that simple junk, badly researched stances and plain untruths are rife throughout the media. For many, many examples of such plainly misinformed ‘journalism’ on climate change issues, just visit BraveNewClimate.com for a taste of the worst.

My comments on Fahn’s piece touch on several issues. First, it’s not just the ‘poor’ country that has problems with respect to ill-equipped reporters – the developed world (and Australia could easily be one of the leaders here) has some particulary terrible coverage of climate change impacts. Second, this problem extends to all environmental issues, not just climate change. Indeed, for some of the most important issues facing humanity today (loss of biodiversity and the ecosystem services they provide), should not the best people be put onto the job? Finally, whatever happened to journalism? Isn’t this supposed to be well-researched, cross-examining, hard-hitting and plain investigation into the affairs affecting everyday life? Instead, too many so-called ‘journalists’ are nothing more than blindly parrotting reporters who wouldn’t know what research was if it came up and bit them on the arse.

Addendum 16 October: I’ve added a little poll below directed toward Australian blog readers:

CJA Bradshaw

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Categories : climate change, ecosystem services, environmental policy, extremism, journalism, media

Wake Up, Freak Out

9 10 2008
© Leo Murray

© Leo Murray

An excellent, short animated film about the perils of climate change and its implications for biodiversity (including humans). Highly recommended.

This really isn’t about polar bears any more. At this very moment, the fate of civilization itself hangs in the balance.

It turns out that the way we have been calculating the future impacts of climate change up to now has been missing a really important piece of the picture. It seems we are now dangerously close to the tipping point in the world’s climate system; this is the point of no return, after which truly catastrophic changes become inevitable.

Wake Up, Freak Out – then Get a Grip is a short, animated film about climate change by Leo Murray.


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Categories : biodiversity, carbon, climate change, climate shift, corruption, ecosystem services, environmental policy, governance, human overpopulation

Conservation Scholars: William Laurance

7 10 2008

This series on ConservationBytes.com takes a page out of our book Tropical Conservation Biology (Sodhi, Brook & Bradshaw) – therein we produced a series of ‘Spotlights’ describing the contributions of great thinkers to conservation science. Each highlight of a Conservation Scholar includes a small biography, a list of major scientific publications and a Q & A on the person’s particular area of expertise.

Our third Conservation Scholar is William Laurance…

Biography

I am a conservation biologist, and am especially interested in assessing the impacts of intensive land uses such as habitat fragmentation, fires, and logging on tropical ecosystems. My team also studies global-change phenomena, such as the effects of global warming on tropical biotas, and I’m broadly interested in conservation policy. Over the past two decades I’ve worked in the Amazon, Central Africa, tropical Australia, and Central America. Why do I work and live in the tropics? I have long been interested in nature conservation, and tropical forests are among the most biologically diverse and imperilled ecosystems on Earth. I was raised far from any rain forest – in the western USA – but I worked in several zoos in my youth and in that way became intrigued by tropical species and communities. When it came time to do my PhD at the University of California, Berkeley, I decided to study the impacts of forest fragmentation on tropical mammals. Later, I started working on tropical trees, and also used remote sensing and geographic information systems to study deforestation and land-use change. Today, I pretty much work on anything – trees, vines, mammals, birds, amphibians – but the one common theme is that my research has a strong conservation focus. I am very much a believer that conservation biologists have to be active conservationists as well. This is especially so in the tropics, where biologists have led international efforts for nature conservation. As president of the Association for Tropical Biology and Conservation, the world’s largest scientific society devoted to the study and protection of tropical ecosystems, I’ve tried to ensure that our organisation plays a leading role in promoting conservation. Our main weapon is our scientific credibility, and the fact that we have a lot of expertise among our members. We’ve fought a number of important conservation battles, and won some of them. Sometimes we feel like the little Dutch boy with his finger in the dike, but if we biologists don’t strive to slow rampant forest destruction, who will?

Major Publications

Questions and Answers

1. Is fragmentation always bad for tropical biodiversity?

It depends what you mean by biodiversity. Whenever there is an environmental change, there are winners and losers. If you fragment a forest, edge-adapted, generalist and exotic species proliferate, whereas old-growth specialists and area-demanding species (such as predators and large-bodied species that are vulnerable to hunting) decline. The reason we worry so much about habitat fragmentation is that the world has plenty of generalist and exotic species; we don’t need to conserve them. The old-growth and area-demanding species, however, are a different story. In a fragmented landscape, their populations often collapse and vanish. So if our goal is to maximise the long-term survival of species – especially those that are most vulnerable to extinction – then habitat fragmentation is almost universally a bad thing. A final consideration is that fragmented landscapes tend to be far more vulnerable to fires, logging, and over-hunting than are intact forests. In the Amazon, for example, fire frequency increases drastically within a few kilometres of forest edges relative to forest interiors. In times-series imagery from satellites, you can see the fragments imploding over time, because rain forests just can’t survive this withering recurrence of destructive fires. Thus, fragmentation is bad from lots of different perspectives.

2. Do you think it is timber logging, agricultural expansion, or global change phenomena that poses the biggest threat to Amazonia this century?

I’d have to say agricultural expansion is the biggest threat, especially for cattle ranching and industrial soy farming, simply because it’s so apparent that it’s devastating vast expanses of forest. Cattle ranching has exploded – the number of cattle in Brazilian Amazonia rose from about 20 million to 60 million head over the last decade – while soy farms have also grown exponentially. Soy farmers not only clear forest themselves, they also buy up a lot of recently cleared land, thereby force ranchers and slash-and-burn farmers to push ever further into the frontier and destroy even more forest. The soy farmers are also a powerful political lobby that is pushing for a massive expansion of highways, roads, and other transportation infrastructure in the Amazon. These new projects are criss-crossing the Amazon and are greatly increasing the pace of forest loss and fragmentation. It’s far harder to predict the effects of global-change phenomena. Some models suggest that increasing deforestation (which reduces evapo-transpiration and hence rainfall) and global warming could both have major impacts on the Amazonian climate. But the different models vary a lot, and the bottom line is that there is still much we don’t understand. The threat from global change might be relatively limited, or it might be massive.

3. Has the Biological Dynamics of Forest Fragment Project (BDFFP) delivered practical conservation outcomes, and can its principles be applied to other tropical regions?

Yes, I think so. We’ve demonstrated, for example, that even remarkably small clearings, such as a powerline corridor or highway, can dramatically inhibit the movements of many rain forest species. We’ve shown that smaller (< 100-hectare) forest fragments rapidly lose many species and exhibit striking changes in their ecology. We’ve also found that edge effects drive many changes in fragmented rain forests, and this has implications for reserve and buffer-zone management, and for the design of wildlife corridors. These are all quite practical conservation outcomes. In general, I think that many of these principles can be applied to other tropical regions, though of course that’s not to suggest that all forests behave similarly. For example, the importance of edge effects may vary quite a lot among different tropical regions.

CJA Bradshaw

(with thanks to Navjot Sodhi, Barry Brook, Ward Cooper, Wiley-Blackwell and Bill Laurance for permission to reproduce the text – buy your copy of Tropical Conservation Biology here)

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Categories : Australia, South America, biodiversity, carbon trading, climate change, conservation, conservation scholars, deforestation, environmental policy, fragmentation, habitat loss, research, tropical

Classics: Fragmentation

3 10 2008
Synergies among threatening processes relative to habitat loss and fragmentation. a) A large population within unmodified, contiguous habitat occupies all available niches so that long-term abundance fluctuates near full carrying capacity (K). b) When habitat is reduced (e.g. 50 % area loss), total abundance declines accordingly. c) However, this simple habitat-abundance relationship is complicated by the spatial configuration of habitat loss. In this example, all remaining fragmented subpopulations might fall below their minimum viable population (MVP) sizes even though total abundance is the same proportion of K as in panel B. As such, limited connectivity between subpopulations implies much greater extinction risk than that predicted for the same habitat loss in less fragmented landscapes. Further synergies (positive feedbacks among threatening processes; black arrows) might accompany high fragmentation, such as enhanced penetration of predators, invasive species or wildfire, micro-habitat edge effects, and reduced resistance to drought with climate change.

Figure 2 from Brook et al. (2008): Synergies among threatening processes relative to habitat loss and fragmentation. a) A large population within unmodified, contiguous habitat occupies all available niches so that long-term abundance fluctuates near full carrying capacity (K). b) When habitat is reduced (e.g. 50 % area loss), total abundance declines accordingly. c) However, this simple habitat-abundance relationship is complicated by the spatial configuration of habitat loss. In this example, all remaining fragmented subpopulations might fall below their minimum viable population (MVP) sizes even though total abundance is the same proportion of K as in panel B. As such, limited connectivity between subpopulations implies much greater extinction risk than that predicted for the same habitat loss in less fragmented landscapes. Further synergies (positive feedbacks among threatening processes; black arrows) might accompany high fragmentation, such as enhanced penetration of predators, invasive species or wildfire, micro-habitat edge effects, and reduced resistance to drought with climate change.

This is, perhaps, one of the most important concepts that the field of conservation biology has identified as a major driver of extinction. It may appear on the surface a rather simple notion that the more ‘habitat’ you remove, the fewer species (and individuals) there will be (see MacArthur & Wilson’s Classic contribution: The Theory of Island Biogeography), but it took us decades (yes, embarrassingly – decades) to work out that fragmentation is bad (very, very bad).

Habitat fragmentation occurs when a large expanse of a particular, broadly defined habitat ‘type’ is reduced to smaller patches that are isolated by surrounding, but different habitats. The surrounding habitat is typically defined a ‘matrix’, and in the case of forest fragmentation, generally means ‘degraded’ habitat (fewer native species, urban/rural/agricultural development, etc.).

Fragmentation is bad for many reasons: it (1) reduces patch area, (2) increases isolation among populations associated with fragments, and (3) creates ‘edges’ where unmodified habitat abuts matrix habitat. Each of these has dire implications for species, for we now know that (1) the smaller an area, the fewer individuals and species in can contain, (2) the more isolated a population, the less chance immigrants will ‘rescue’ it from catastrophes, and (3) edges allow the invasion of alien species, make the microclimate intolerable, increase access to bad humans and lead to cascading ecological events (e.g., fire penetration). Make no mistake, the more fragmented an environment, the worse will be the extinction rates of species therein.

What’s particularly sad about all this is that fragmentation was actually seen as a potentially GOOD thing by conservation biologists for many long years. The so-called SLOSS (Single Large or Several Small) debate pervaded the early days of conservation literature. The debate was basically the argument that several small reserves would provide more types of habitat juxtapositions and more different species complexes, making overall diversity (species richness) higher, than one large reserve. It was an interesting, if not deluded, intellectual debate because both sides presented some rather clever theoretical and empirical arguments. Part of the attraction of the ‘Several Small’ idea was that it was generally easier to find series of small habitat fragments to preserve than one giant no-go area.

However, we now know that the ‘Several Small’ idea is completely inferior because of the myriad synergistic effects of fragmentation. It actually took Bruce Wilcox and Dennis Murphy until 1985 to bring this to everyone’s attention in their classic paper The effects of fragmentation on extinction to show how silly the SLOSS debate really was. It wasn’t, however, until the mid- to late 1990s that people finally started to accept the idea that fragmentation really was one of the biggest conservation evils. Subsequent work (that I’ll showcase soon on ConservationBytes.com) finally put the nail in the SLOSS debate coffin, and indeed, we haven’t heard a whisper of it for over a decade.

For more general information, I invite you to read the third chapter in our book Tropical Conservation Biology entitled Broken homes: tropical biotas in fragmented landscapes, and our recent paper in Trends in Ecology and Evolution entitled Synergies among extinction drivers under global change.

CJA Bradshaw

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Categories : conservation, deforestation, extinction debt, fragmentation, invasive species, island biogeography, living dead, protected area, reserve

Potsdam Initiative: Economics of Ecosystems and Biodiversity

1 10 2008

A recent report from the European Union with which I was marginally involved has been published online.

The meeting of the environment ministers of the G8 countries and upcoming industrialising countries took part in what has been dubbed the ‘Potsdam Initiative‘ have commissioned a series of reports on the ‘Economic significance of the global loss of biological diversity’.

I quote:

‘In a global study we will initiate the process of analysing the global economic benefit of biological diversity, the costs of the loss of biodiversity and the failure to take protective measures versus the costs of effective conservation.’

The first stage was the report was entitled ‘The Economics of Ecosystems & Biodiversity (TEEB)’. Mr Pavan Sukhdev, Managing Director and Head of Deutsche Bank’s Global Markets business in India, and a Founder-Director of the ‘Green Accounting for Indian States Project’, an initiative of the Green Indian States Trust (GIST) to set up an economic valuation and national accounting framework to measure sustainability for India, was recently appointed as the independent Study Leader.

The overall aims of the study are to evaluate the costs of the loss of biodiversity and the associated decline in ecosystem services, and to compare them with the costs of effective conservation and ‘sustainable’ use. The overall aim is to increase awareness of the value of biodiversity and ecosystem services to facilitate the development of cost-effective policy responses to the problem.

The interim report is available here, and the final report will be published shortly on the dedicated website here. The title of the final report of the first phase is THE ECONOMICS OF ECOSYSTEMS AND BIODIVERSITY: SCOPING THE SCIENCE.

I was involved specifically in Section 4.13 ‘Regulation of Natural Hazards’ which are defined ‘as infrequent natural phenomena that – during a relatively short period of time – pose a high level of threat to [human] life, health or property. These include seismic events (volcanic eruptions, earthquakes, tsunamis), extreme weather events (hurricanes, floods), avalanches and land slides. My contribution was mainly with respect to the role of deforestation on flood risk.

The report was jointly prepared by Ana Rodrigues and Andrew Balmford.

CJA Bradshaw

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Categories : conservation, deforestation, ecosystem services, environmental policy, flood, governance, habitat loss