Subtle threats could ruin the Amazon rainforest
An interview with Amazon scientist Dr. Carlos Peres
Rhett A. Butler,
November 7, 2007

While the mention of Amazon destruction usually conjures up images of vast stretches of felled and burned rainforest trees, cattle ranches, and vast soybean farms, some of the biggest threats to the Amazon rainforest are barely perceptible from above. Selective logging -- which opens up the forest canopy and allows winds and sunlight to dry leaf litter on the forest floor -- and 6-inch high "surface" fires are turning parts of the Amazon into a tinderbox, putting the world's largest rainforest at risk of ever-more severe forest fires. At the same time, market-driven hunting is impoverishing some areas of seed dispersers and predators, making it more difficult for forests to recover. Climate change -- and its forecast impacts on the Amazon basin -- further looms large over the horizon.

Dr. Carlos Peres in the forest along the Rio Roosevelt in the Brazilian Amazon
Few people understand these threats better than Dr. Carlos Peres of the University of East Anglia, a native Brazilian who grew up in an Amazonian city with the rainforest as his backyard. Through affiliations with a roster of universities, Peres has worked extensively in the Amazon on topics ranging from surface fires to wildlife ecology to sustainable development. He has been honored by Time Magazine as an "Environmentalist Leader for the New Millennium" (2000), published more than 150 papers, and recently co-edited a definitive book on tropical deforestation (Emerging Threats to Tropical Forests).

In a November 2007 interview with, Peres fielded questions about his work, his outlook for the Amazon forest, and the challenges facing rainforest conservation efforts.


Mongabay: What is the focus of your research?

Emerging Threats to Tropical Forests
(University Of Chicago Press, 2006)
Peres: Over the last 25 yrs, I've courted a variety of themes in ecology and conservation in over 80 Neotropical forest sites, but the main unifying focus is to understand the effects of land-use change, large-scale habitat disturbance and game harvest on tropical forest biodiversity. For example, I've worked on the effects of forest fragmentation, selective logging, surface fires, slash-and-burn agriculture, secondary succession, forest conversion to fast-growing tree monocultures, and subsistence hunting on forest wildlife. I'm also interested in more fundamental questions in relation to large-scale spatial patterns of population abundance and species diversity in tropical forests, and how those are governed by baseline environmental gradients like rainfall seasonality, geochemistry, soil fertility and floristic composition.

Mongabay: How did you become interested in this area? What is your background?

Peres: I was fortunate to be born and educated in a major Amazonian city in the 1960s, with the world's largest tropical forest in my backyard, when less than 1% of Brazilian Amazonia had been deforested. I've been interested in animals, both small and large, for as long as I can remember. My mother recalls that I followed columns of harvest ants for hours around our house before I could even walk properly. That interest gradually morphed into several naturalistic hobbies which flourished in my father's ~3,500-hectare landholding (97% of which was primary forest) along the Rio Acará (90 km south of Belém) which was also a spiritual retreat. At the young age of 16, I later became a research intern at Museu Emílio Goeldi in Belém (the premier Amazonian Natural History research institute) and had the fortune of joining many collecting expeditions and working for 4 yrs with the leading zoologists and botanists plowing their trade in the Amazon in the early 1980s. By then I was avid to take my chances and follow a science career in tropical ecology and conservation. So my background is very eclectic and I've worked on the population and community ecology of Neotropical forest trees, seedlings, arthropods, freshwater fishes, herps, birds and mammals, and in both disturbed and undisturbed forests.

Mongabay: Do you have any advice for students hoping to become conservation scientists?

Peres: Perseverance and persistence. In today's severely competitive world, it's not exactly straightforward to conquer a career in tropical conservation, but the opportunities are there for the most obstinate students who are prepared to go to great lengths to earn a place in the sun. But there are many ways one can become useful in conservation, and that includes conservation policy, advocacy and action, so conservation science is not the be-all and end-all for everyone.

Mongabay: What is you favorite place in the tropics?

Peres: That's a really tough choice, but it would have to be a wide swathe of Amazonian seasonally flooded forest (várzea or igapó) at its maximum water-level when you can canoe your way silently through the midstorey early in the morning, at almost eye-level with the subcanopy wildlife, some 12 m above where you'd be walking only 6 months earlier.

Mongabay: What is your outlook for the Amazon in 20 years time? What do you see as the greatest threats to the ecosystem? Do you see climate change as a significant threat to the Amazon's tropical forest ecosystem? What is the impact of wildfires--especially recurrent burning--on plants and wildlife in forests that do not typically experience burning?

Surface fire burning in the Brazilian Amazon. Photo by Jos Barlow
Peres: At current rates of deforestation and forest degradation by logging, wildfires and forest fragmentation, two decades is a very long time for the Amazon, so the most robust projections of future forest cover and forest intactness scenarios look pretty bleak. The pace of government-sponsored agricultural resettlement programs, road-building, other infrastructure expansion and ensuing forest conversion is not exactly slowing down, and we're yet to be able to show that market-integrated forest dwellers, whether they are indigenous, 19th-20th Century immigrants, or neocolonists, can make a decent living in the long-term while coexisting with a reasonably intact forest cover. But the most extensive threat to the very viability of vast tracts of closed-canopy Amazonian forest ecosystems is logging, because timber extraction changes the forest microclimate primarily by opening up the canopy and drying down the understorey, thereby eroding the natural immunity of the forest against recurrent surface fires. Because this was never part of the evolutionary history of rainforests, most of the Amazonian biota is extremely sensitive to even low-intensity fires, which can trigger mass delayed die-offs of trees and woody lianas, thereby adding to the fuel load and paving the way to even more severe recurrent fires. And under current scenarios of climate change, the unusual seasonal droughts that we have seen in the last decade will become even more severe and more frequent, exacerbating the spread of the onset of a fire-dominated disturbance regime that, as we have shown in our work, will dramatically impoverish the structure and species composition of Amazonian forests, in many cases irreversibly. As a result of recurrent fires and wholesale mortality of old-growth canopy trees, high-biomass closed-canopy primary forests can gradually slip into a system dominated by low-biomass trees and shrubs with fast life histories that is more akin to a scrubby secondary forests, and this has huge implications to both biodiversity retention, water cycling and carbon storage.

Mongabay: How important, in terms of scale and impact on biodiversity, is hunting in tropical forests?

Three White-lipped peccaries entering a village on the way to the pot. Photo by Luke Parry
Peres: Game harvest is arguably the most widespread form of tropical forest disturbance, and amounts to profound consequences to the structure of large vertebrate communities. Yet hunting is a diffuse and relatively invisible activity that takes place underneath the canopy and is virtually undetectable at large spatial scales so this cannot be easily mapped using any conventional remote sensing approach from the comfort of your armchair. Admittedly, hunting only affects a very small proportion of all vertebrate species in a tropical forest because in most cases both subsistence and commercial hunters cannot afford to be unselective, and most species are too small and simply not worth pursuing. However, the large-bodied vertebrate fauna that is frequently decimated by overhunting has a disproportionately large contribution to the structure and functioning of these ecosystems in terms of their high crude biomass, their trophic roles, as agents of physical disturbance, and their direct or indirect ecological interactions with other species which often govern plant reproductive fitness. The bottom-line is that a tropical deciduous or a tropical evergreen forest without the large mammals, large birds and large reptiles with which they have evolved can never be defined as an intact, healthy ecosystem — complete with all its constituent parts — no matter how undisturbed the physical structure of the forest appears to be. And seeing the wood for the trees in a tropical forest means that you have to consider the full complement of species in what were once pristine forest systems, replete with all creatures great and small.

Mongabay: What is the best way to address hunting?

Peres: Game harvest in itself is not a bad thing. Subsistence hunters one way or the other can help justify maintaining forest wildlife habitat in millions of hectares in the form of extractive and indigenous reserves, just like recreational game hunting can be a huge boost to wildlife conservation in many temperate countries. The problem is that local game populations need to be managed carefully, and in tropical forests worldwide we're still a long ways off from being able to do that — not least because we still lack the basic information, implementation tools and know-how that is grounded in applied ecological research. As a consequence, many game species are often severely overhunted or driven to local extinction. For a start, the safest way to protect many harvest-sensitive game species is to make sure that sufficiently large populations are effectively protected from any kind of harvest in different categories of forest reserves. But these reserves will unavoidably account for but a relatively small proportion of the ecological distribution of these species, so we also need to work with local [tribal and nontribal] communities who depend on wildlife resources both within legally occupied protected areas and outside formal reserves. In some cases these resources can be co-managed by local communities and there are a number of measures that can help spread the burden of hunting pressure both spatially and across game species of varying desirability and resilience to hunting, thereby prevent overharvesting of any given stock. The issue of both small and large domestic livestock substitution remains controversial, but in some cases that, too, can help relieve the pressure on those species that are most susceptible to population declines where hunting can and should take place. But some low-fecundity species are just too sensitive to even low-intensity offtakes, and although those could also be managed in theory, it is extremely difficult to be able to achieve truly sustainable harvests in practice, so in many cases those populations will be safest if they are not harvested at all at any given site, either temporarily or permanently. Finally, in many tropical forest countries we still lack the basic institutional framework, rural extension mechanisms and a technical advisory protocol that can ensure the link between what we already know now about natural resource management and the implementation of management policies at local, regional or national scales.

Mongabay: What have you learned from indigenous use of forest resources in the Amazon?

A young Kaxinawa hunter with a howler and a white-faced capuchin monkey. Photo courtesy of Dr. Peres
Peres: Indigenous peoples are not necessarily wise guardians of the forest and forest resources. For centuries and millennia they were able to coexist harmoniously with relatively intact systems because these populations in almost all cases were very sparsely settled, and there were many density-dependent mechanisms, such as diseases, warfare, and mutual avoidance, to keep their numbers and distribution in the landscape in check. Unlike many parts of the Old World, they also lacked the technology to impart rapid wholesale changes in the structure of the ecosystem. Having said that, I am a profound admirer of the way Indians live and have worked with three indigenous groups in different poles of the Amazon who have taught me a great deal about the forest. In many cases, many generations of trial and error experimenting with the flora have molded a body of ethnobotanical knowledge that is unrivalled anywhere else. Yet, slowly but surely, these populations are still losing out to outside conquistadores, so we must make sure that we can ensure indigenous territorial rights, and most importantly be able to work with them as the logging, mining and agricultural frontiers inevitably close in on them.

Mongabay: What do you see as the best way to protect tropical ecosystems and conserve biodiversity for future generations?

The Amazon forest going up in flames. Photo courtesy of Dr. Carlos Peres

Slash-and-burn plot after a deforestation fire in Alta Floresta in the Brazilian Amazon. Photo by Alex Lees
Peres: The backbone of any national scale strategy to ensure the persistence of all species in any native biota well into the future has to be a robust, representative network of sufficiently large protected areas that are created and implemented by the state or federal government. In the case of tropical forests, these preserves should always ensure largely intact forest cover but to some degree they could vary in the form in which they can be used, all the way from strictly protected areas that exclude all consumptive uses to those that are occupied by manageable numbers of legal residents harvesting sustainable quotas of nontimber forest products. This basic strategy should also be complemented by other approaches such as forest reserves inside private landholdings, benign extractive and forestry activities in the wider unprotected forest matrix, and appropriate design of landscapes dominated by agro-forestry or conventional agriculture. But given the socioeconomic realities of different countries, the opportunities and financial viability of creating sizeable protected areas of old-growth forest are rapidly diminishing, so it is crucial that we act sooner rather than later. And there is also the issue of permanence in that most protected areas, or the legislation ensuring their status continuity, will come under mounting pressure as the world's last tropical forest regions are developed and rural populations grow, so it is crucial that protected areas are designed and created to endure the test of time. This may require continuous vigilance on the part of national and international conservation organizations, and field and/or remote-sensing based monitoring programs so that we can be sure that these conservation units are performing well and delivering their original biodiversity conservation objectives.

Mongabay: What can the general public do at home to help?

Dr. Peres's PhD study area in the Urucu (700 km southwest of Manaus) showing a vast landscape of completely undisturbed forest. Photo courtesy of Dr. Peres
Peres: Ordinary well-meaning people can support conservation organizations that strive to minimize trickle-down administrative inefficiencies by plowing most, if not all, of their conservation dollars or euros directly into sound biodiversity conservation projects on the ground. But there's also a policy arena that anyone can influence by lobbying politicians and decision-makers, and becoming involved in the main conservation debates of our times. But to do that, concerned citizens will have to think globally and beyond local constituencies because the most decisive conservation problems of our times may be happening in far-flung places that we may never have a chance to see.

About Dr. Carlos A. Peres

Carlos Peres, born in Belém, Brazil (1963); Tropical forest ecologist and Conservation Biologist; originally trained as a tropical field biologist and tropical agronomist. Education: University of Pará (Brasil), University of Florida (USA), University of Cambridge (UK), and Duke University (USA); later a Professor of Ecology at University of São Paulo (Brasil), and currently a Reader in Conservation Biology at the University of East Anglia (UK).

  • Dr Carlos A Peres
  • Bay Biodiversity Awards -- Carlos Peres

    Carlos is a member of the Association for Tropical Biology and Conservation (ATBC), the largest association of tropical scientists in the world. The 2008 meeting will take place in Suriname:

    Rhett A. Butler, (November 07, 2007).

    Subtle threats could ruin the Amazon rainforest.