Humans have altered tropical forests for 45,000 years

Aug. 4 (UPI) -- A new study reveals that humans have had a global impact on tropical forests for at least 45,000 years, contrary to the belief that those forests are untouched.

The study, published Aug. 3 in Nature Plants, is the first review of the global impact of humans on tropical forests.

Researchers found that humans have been having a dramatic impact on tropical forest ecologies through controlled burns to plant and animal management to clear cutting.

Scientists from the Max Planck Institute for the Science of Human History, Liverpool John Moores University, University College London and École française d'Extrême-Orient examined three phases of human impact on tropical forests, roughly correlating to hunting and gathering, small-scale agricultural activities and large-scale urban settlements.

As early as 45,000 years ago, groups of hunter-gatherers burned areas of tropical forests in Southeast Asia, and researchers found evidence of similar activities in Australia and New Guinea. This clearing of the forest allowed early humans to create forest-edge environments that encouraged the presence of animals and plants as a food source.

Researchers found the earliest evidence of farming in tropical forests in New Guinea 10,000 years ago to supplement hunting and gathering efforts. Groups using indigenous tropical forest agricultural strategies did not have lasting impacts on the tropical forests.

"Indeed, most communities entering these habitats were initially at low population densities and appear to have developed subsistence systems that were tuned to their particular environments," Dr. Chris Hunt of Liverpool John Moores University, said in a news release.

As agricultural intensity increased, the effects on tropical forests had a longer lasting impact.

When agriculturalists bringing pearl millet and cattle moved to the area of tropical forests in western and central Africa about 2,400 years ago, significant soil erosion and forest burning occurred.

"These practices, which induce rampant clearance, reduce biodiversity, provoke soil erosion, and render landscapes more susceptible to the outbreak of wild fires, represent some of the greatest dangers facing tropical forests," Hunt said.

Researchers concluded that the perception of an untouched tropical forest ecosystem does not exist.

"Indigenous and traditional peoples - whose ancestors' systems of production and knowledge are slowly being decoded by archaeologists - should be seen as part of the solution and not one of the problems of sustainable tropical forest development," Dr. Patrick Roberts, of the Max Planck Institute said.