Half of Amazon’s trees could be lost forever

New roads, agriculture, logging and mining are claiming an increasingly large area of once pristine Amazon forest, observe an international team of researchers.

Writing in the journal Proceedings of the National Academy of Sciences, they assessed how accurate the extinction rate of tree species in the South American biodiversity hotspot.

Using projections in the UN’s Millennium Ecosystems Assessment as the bench mark, the scientists estimated the number, abundance and range of the region’s trees to compile optimistic and non-optimistic scenarios.

Within the Brazilian portion of the Amazon Basin, they calculated that there were 11,210 tree species with a trunk diameter (at breast height) of more than 10cm.

Of these, 3,248 had populations of more than one million specimens. The team said that under both scenarios would persist in the future.

However, at the rare end of the abundance spectrum, the researchers suggested that there were about 5,308 species with fewer than 10,000 trees remaining.

Under the non-optimistic scenario, about half of these species were likely to go extinct.

Even under the optimistic scenario, more than a third faced extinction, with about 37% being lost forever.

The team said that many of the less abundant species had small ranges and were very vulnerable to habitat loss.

Looking at all tree species, the scientists warned that the rate of extinction was forecast to be 33% under the non-optimistic scenario.

Even under the optimistic scenario, they warned that the extinction rate would result in a fifth of the trees in the Brazilian Basin disappearing.

Source: PNAS

Date: 11/08/2008

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