Extinction most likely for rare trees in the Amazon rainforest

August 14th, 2008 - 4:30 pm ICT by ANI  

Washington, August 14 (ANI): Scenarios based on a neutral theory has suggested that rare trees in the Amazon rainforest are more likely to go extinct than common species.

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.

The Amazon basin contains about 40 percent of the worlds 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 Fishers alpha statistic and the other based on Prestons 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 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 Panamas 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.

In this offering, the authors use the neutral theory to predict the number of tree species and to test predictions of the Millenium Ecosystems Assessment that forecasts major tree extinctions in the Amazon over the next several decades.

First, they estimate that the Brazilian Amazon has (or had) 11,210 large tree species, and, of these, 5,308 species are classified as rare.

Based on optimistic and non-optimistic scenarios for road construction in the Amazon published by the Smithsonians William Laurance and colleagues in the journal Science in 2004, they predict that the rare species will suffer between 37 and 50 percent extinction, whereas the extinction rate for all trees could be from 20 to 33 percent overall. (ANI)

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