Washington, August 17 (ANI): A new study has determined that massive burning of forests for agriculture thousands of years ago may have increased atmospheric carbon dioxide (CO2) enough to alter global climate and usher in a warming trend that continues today.
The study was carried out by researchers at the University of Virginia and the University of Maryland-Baltimore County (UMBC) in the US.
Researchers said that today's 6 billion people use about 90 percent less land per person for growing food than was used by far smaller populations early in the development of civilization.
Those early societies likely relied on slash-and-burn techniques to clear large tracts of land for relatively small levels of food production.
"They used more land for farming because they had little incentive to maximize yield from less land, and because there was plenty of forest to burn," said William Ruddiman, the lead researcher and a professor emeritus of environmental sciences at the University of Virginia.
"They may have inadvertently altered the climate," he added.
According to projections from some models of past land use, large-scale land clearing and resulting carbon emissions have only occurred during the industrial era, as a result of huge increases in population.
But Ruddiman, and his co-author Erle Ellis, an ecologist at UMBC who specializes in land-use change, said that these models are not accounting for the possibly large effects on climate likely caused by early farming methods.
"Many climate models assume that land use in the past was similar to land use today; and that the great population explosion of the past 150 years has increased land use proportionally," Ellis said.
"We are proposing that much smaller earlier populations used much more land per person, and may have more greatly affected climate than current models reflect," Ellis added.
Ruddiman and Ellis based their finding on several studies by anthropologists, archaeologists and paleoecologists indicating that early civilizations used a great amount of land to grow relatively small amounts of food.
The researchers compared what they found with the way most land-use models are designed, and found a disconnect between modeling and field-based studies.
"It was only as our populations grew larger over thousands of years, and needed more food, that we improved farming technologies enough to begin using less land for more yield," Ruddiman said.
"We suggest in this paper that climate modelers might consider how land use has changed over time, and how this may have affected the climate," he added. (ANI)