Extinction most likely for rare trees in the Amazon ...( Common tree species in the Amazon wi...)

Common tree species in the Amazon will survive even grim scenarios of deforestation and road-building, but rare trees could suffer extinction rates of up to 50 percent, predict Smithsonian scientists and colleagues in the Aug. 12 issue of the journal Proceedings of the National Academy of Science.

How resilient will natural systems prove to be as they weather the next several decades of severe, human-induced global change? The debate is on between proponents of models that maximize and minimize extinction rates.

The Amazon basin contains about 40 percent of the world's remaining rainforest. One of the fundamental characteristics of tropical forests is the presence of very rare tree species. Competing models of relative species abundance, one based on Fisher's alpha statistic and the other based on Preston's lognormal curve, yield different proportions of rare trees in the forest.

Thirty years ago Stephen P. Hubbell, senior scientist at the Center for Tropical Forest Science of the Smithsonian Tropical Research Institute and distinguished professor in the Department of Ecology and Evolution at the University of California, Los Angeles, and his colleague Robin Foster, now at the Field Museum in Chicago, set up a unique experiment to monitor the growth, birth and death of more than 250,000 tropical trees on Panama's Barro Colorado Island. This large "forest dynamics plot" would generate the data needed to build good models that include rare species.

Today the Center for Tropical Forest Science coordinates a Global Earth Observatorya network of 20 such forest study sites in 17 countries, which maintains "actuarial tables" for more than 3 million trees.

Hubbell works with data from the network to develop and test his neutral theory of biodiversityan attempt to find a unified explanation of large, complex biological systems that accurately predicts the outcome of major ecological and evolutionary forces of change.

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