PALO ALTO, Calif., Sept. 3 (UPI) -- More than 80 percent of the new farmland created in the tropics since 1980 has come from felling forests, which drives global warming, researchers say.
A study led by a Stanford University researcher says global agricultural expansion cut huge swaths through forests, mostly tropical forests, from 1980 to 2000 when half a million acres of new farmland was created, a university release said.
"This has huge implications for global warming, if we continue to expand our farmland into tropical forests at that rate," Holly Gibbs, a postdoctoral researcher in the Department of Environmental Earth System Science, said.
Gibbs and colleagues at several universities analyzed Landsat satellite data and images from the United Nations.
"Every million acres of forest that is cut releases the same amount of carbon into the atmosphere as 40 million cars do in a year," Gibbs said.
Most of the carbon release comes from burning the forests, but even if the felled trees are simply left in place the bulk of the carbon from the plants makes its way into the atmosphere during decomposition, she said.
But there are encouraging signs, Gibbs said.
During the 1990s, more of the deforestation was done by large corporate-run farms rather than by small family farms as was the case in the 1980s.
Big agribusiness tends to be more responsive to global economic signals as well as pressure campaigns from advocacy organizations and consumer groups, Gibbs said.