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…
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?
- Laurance W. F. & Bierregaard R. O. J. (1997) Tropical Forest Remnants: Ecology, Management and Conservation of Fragmented Communities. University of Chicago Press, Chicago
- Laurance W. F., Cochrane M. A., Bergen S., Fearnside P. M., Delamonica P., Barber C., D’Angelo S. & Fernandes T. (2001) The future of the Brazilian Amazon. Science 291, 438-439
- Laurance W. F., Laurance S. G., Ferreira L. V., Rankinde Merona J. M., Gascon C. & Lovejoy T. E. (1997) Biomass collapse in Amazonian forest fragments. Science 278, 1117-1118
- Laurance W. F., Lovejoy T. E., Vasconcelos H. L., Bruna E. M., Didham R. K., Stouffer P. C., Gascon C., Bierregaard R. O., Laurance S. G. & Sampaio E. (2002) Ecosystem decay of Amazonian forest fragments: A 22-year investigation. Conservation Biology 16, 605-618
- Laurance W. F. & Peres C. A. (2006) Emerging Threats to Tropical Forests. University of Chicago Press, Chicago
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.
(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)