Destructive farming practices of early civilization may have altered climate long before industrial era
Jeremy Hancemongabay.com
August 31, 2009
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Since publishing his theory Ruddiman, professor emeritus of environmental science at the University of Virginia, has been busy answering critics. He has explored how early rice paddies could have released large amounts of methane into the atmosphere and developed a model that shows how the burning of the world's then pristine forests could have lead to a positive feedback mechanism, since the carbon released by the forests could have raised ocean temperatures.
 Contemporary deforestation by burning in Laos. Photo by: Rhett A. Butler. |
"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 Ruddiman. "They may have inadvertently altered the climate."
Due to the large amount of forested land, Ruddiman argues, that farmers used a rotation method for agriculture: once early farmers saw yields decline in one area they would simply burn more forest and begin planting in new fields. This could have led to a situation where five times more land was deforested than was actually farmed at any given time.
"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."
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