PRISTINE PARTS of the Amazon rainforest that were thought to have escaped the effects of human encroachment have changed dramatically over the past 20 years, scientists have determined.
The delicate balance of tree species growing in some of the most remote regions of the Amazon has been altered significantly and the scientists believe it is a direct result of increases in carbon dioxide emissions caused by humans. Small, slower-growing trees that thrived beneath the forest canopy are losing out to faster-growing varieties because the Amazon is in effect being artificially "fertilised" with increased levels of carbon dioxide in the atmosphere.
The result is a change in the composition of the major groups of trees, which could have a long-term impact in the vital role played by the Amazon in soaking up excess carbon dioxide, the scientists said. Amazonian rainforests are renowned for their rich diversity of trees. But some areas appear to be doing better at the expense of others, as atmospheric levels of carbon dioxide continue to rise, said William Laurance of the Smithsonian Tropical Research Institute. For the past two decades, the scientists, whose study is published in the journal Nature, tracked the growth of nearly 14,000 trees in 18 plots of land which were scattered throughout 120 square miles.
Dr Laurance said the researchers deliberately chose the plots because they were remote and well away from any human activity, such as logging and deforestation, but the changes they saw were nevertheless dramatic. He added: "The changes in Amazonian forests really jump out at you. It's a little scary to realise that seemingly pristine forests can change so quickly and dramatically.
"Sadly, this could be a signal that the forest's ecology is changing in fundamental ways. Tropical rainforests are renowned for having lots of high specialised species. If you change the tree communities then other species - especially the animals …