The Telegraph reports,
Farmers who used “slash and burn” methods of clearing forests to grow crops thousands of years ago could have increased carbon dioxide levels enough to change the climate, researchers have claimed.
The US scientists believe that small populations released carbon emissions as they cleared large tracts of land to produce relatively meagre amounts of food.
They were much less efficient than farmers using today’s agricultural practices because there were no constraints on land.
A study published online in the journal Quaternary Science Reviews by researchers at the University of Virginia and the University of Maryland-Baltimore County (UMBC) said that early farmers could have cleared five or more times as much land as they used at any one time.
According to the researchers, today’s population of six billion people uses about 90% less land per person for growing food than the early farming societies.
William Ruddiman, the paper’s lead author and emeritus professor of environmental sciences at the University of Virginia, said the early farmers were likely to have cleared land by burning forests, planted crop seeds among the dead stumps and moved on to a new area once the yields declined.
“They used more land for farming because they had little incentive to maximise yield from less land, and because there was plenty of forest to burn. They may have inadvertently altered the climate,” he said.