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A world of trees

Amazon Forest: The tropical Americas may not be the site of the greatest tree diversity

LÉO RAMOSAmazon Forest: The tropical Americas may not be the site of the greatest tree diversityLÉO RAMOS

Amidst the vastness of tropical forests, scientists remain clueless as to how many tree species actually exist. A comprehensive study has compiled data from forest inventories conducted in over 200 locations lying between the tropics of Cancer and Capricorn (a region known as the Neotropics), recording over 11,000 species (PNAS, June 16, 2015). However, statistical analyses suggest that the region is likely home to at least 40,000 and possibly more than 53,000 species of trees, a figure much higher than previous estimates. A surprising discovery was that the Indo-Pacific region is as species-rich as the Neotropics, once considered the undisputed champion of tree diversity. Taking into account the survey’s margin of error, the two regions are likely to be home to between 19,000 and 25,000 species, at least. Continental Africa is much less diverse in arboreal terms, with a minimum of 4,500 to 6,000 tree species. These findings are consistent with the hypothesis that African forests suffered a drastic reduction in the Pleistocene epoch, leaving only a small number of species for the diversification that came later, with the forest expansion. The study involved dozens of researchers, including 29 Brazilians from 17 institutions. A word of warning: most of those species are rare, indicating a high risk of extinction through deforestation.