Study: Evidence shows human effects on Asian forests for 11,000 years

Jan. 24, 2014 at 5:11 PM
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BELFAST, Northern Ireland, Jan. 24 (UPI) -- Southeast Asia tropical forests, long thought unaffected by humans in the past, have in fact been shaped by humans for the last 11,000 years, scientists say.

While rainforests in Borneo, Sumatra, Java, Thailand and Vietnam were previously thought to have been largely unaffected by human presence, evidence suggests otherwise, researchers from Queen's University Belfast reported Friday.

A study of pollen samples across the three islands and the Southeast Asian mainland revealed a pattern of repeated disturbance of vegetation since the end of the last ice age, approximately 11,000 years ago, Queen's palaeoecologist Chris Hunt said.

"It has long been believed that the rainforests of the Far East were virgin wildernesses, where human impact has been minimal. Our findings, however, indicate a history of disturbances to vegetation," he said. "While it could be tempting to blame these disturbances on climate change, that is not the case as they do not coincide with any known periods of climate change. Rather, these vegetation changes have been brought about by the actions of people."

Because traditional archaeological methods of locating and excavating sites are extremely difficult in dense forests, evidence of human activity in rainforests is extremely difficult to find, he said, but pollen samples and a major review of existing palaeoecology research suggest human activities.

"There is evidence that humans in the Kelabit Highlands of Borneo burned fires to clear the land for planting food-bearing plants," Hunt said. "Pollen samples from around 6,500 years ago contain abundant charcoal, indicating the occurrence of fire."

While naturally occurring fires would usually be followed by specific weeds and trees that flourish in charred ground, evidence shows many fires were followed by the growth of fruit trees, suggesting people intentionally cleared forest vegetation and planted sources of food in its place, he said.

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