ATBC 2008 - Laurance

Symposium

Are We Developing a Distorted View of Tropical Biology

Organizer : William Laurance (laurancew -at- si.edu)

Many of the world’s leading tropical research centers, such as Barro Colorado Island in Panama, La Selva in Costa Rica, Los Tuxtlas in Mexico, and Pasoh in Peninsular Malaysia, are now fragments or man-made islands surrounded by drastically modified landscapes. Even some of the historically most-remote research centers, such as the Biological Dynamics of Forest Fragments Project in central Amazonia, and Lambir in Malaysian Borneo, suffer from moderate to severe hunting and other forms of human encroachment. The pervasiveness of such threats across the tropics raises a crucial question: because so much research in based in these key areas, are we developing a distorted view of tropical biology?

Available evidence suggests that fundamental changes in ecological and ecosystem processes could be occurring in many areas. Many fragmented research sites have an absence or abnormally low abundances of megafauna and large predators, such as tigers, jaguars, pumas, harpy eagles, elephants, and tapirs. The loss of large, regulating predators may have important effects on their prey species and food webs. For example, in Pasoh and La Selva, bearded pigs and peccaries have at times become hyperabundant, possibly because of predator declines and also possibly because they favor mosaics of forest and agriculture. At La Selva and possibly elsewhere, survival and regeneration of large-seeded tree species has declined relative to areas outside the reserve, possibly because of high peccary numbers. Many isolated reserves, such as Barro Colorado Island and La Selva, have lost significant numbers of understory bird species, which typically favor forest interiors and are sensitive to forest fragmentation and edge effects. Alterations of the surrounding landscape can have major effects on forest ecosystems; for example, recurring wind damage may be altering forest dynamics and composition on Barro Colorado Island. If such changes are ubiquitous, we may be experiencing a “shifting baseline,” such that our perception of the characteristics and functioning of intact ecosystems is becoming increasingly biased and different from true “natural” conditions.

However, the nature and generality of such changes, and their impacts on tropical ecology, are controversial and poorly understood. In this symposium I propose to bring together leading scientists studying ecological characteristics and changes in leading tropical research sites. I will balance the program to some extent by inviting individuals who maintain that the ecological characteristics of tropical reserves have either been little impacted or at least still provide a reasonably unbaised view of tropical forest ecology.