London: Man-made global warming may have little effect on some common species of trees in the Amazon rainforest as they date back more than 8 million years and have survived through massive temperature fluctuations, scientists claim.
Some of the Amazonian species are more than 5 million years older than previously thought, and have survived warm periods similar to the worst case scenarios forecast for 2100, according to a new study.
"In the absence of other major environmental changes, near-term high temperature-induced mass species extinction is unlikely," said researcher Christopher Dick, of the University of Michigan.
The new study is at odds with earlier papers, which were based on ecological niche-modeling scenarios, that predicted tree species extinctions in response to relatively small increases in global average air temperatures, the `Daily Mail` reported.
Dick and colleagues used a molecular clock approach by studying mutations in DNA to determine the ages of 12 widespread Amazonian tree species, including the kapok and the balsa.
They looked at climatic events that have occurred since those tree species emerged and inferred that in general, the older the age of the tree species, the warmer the climate it has previously survived.
Nine of the tree species have been around for at least 2.6 million years, seven have been present for at least 5.6 million years, and three have existed in the Amazon for more than 8 million years.
"These are surprisingly old ages. Previous studies have suggested that a majority of Amazon tree species may have originated during the Quaternary Period, from 2.6 million years ago to the present," Dick said.
Air temperatures across Amazonia in the early Pliocene Epoch (3.6 million to 5 million years ago) were similar to Intergovernmental Panel on Climate Change projections for the region in 2100 with moderate carbon emissions.
Air temperatures in the late Miocene Epoch - 5.3 million to 11.5 million years ago - were about the same as IPCC projections for the region in 2100 using the highest carbon-emission scenarios.
"Our paper provides evidence that common Neotropical tree species endured climates warmer than the present, implying they can tolerate near-term future warming under climate change," Dick added.
Co-author Simon Lewis, of University College London, said that while the findings were good news it did not lessen the problems posed by global warming and the threats posed to the Amazon by deforestation.
The study was published in the journal Ecology and Evolution.