MADISON, Wis., Nov. 1 (UPI) -- As croplands expand at the expense of native ecosystems such as forests, nature loses capacity to protect the world from climate change, U.S. researchers say.
Researchers at the University of Wisconsin-Madison say ecosystems' capacity to store carbon, the element at the heart of global climate problems, is steadily eroding as growing numbers of natural ecosystems give way to agriculture, a university release said Monday.
The effect is most acute in the tropics, where expanding agriculture often comes at the expense of the tropical forests that act as massive carbon sinks because of their rich diversity and abundance of plant life, researchers say.
"We analyzed the trade-offs between carbon storage and crop production at a level of detail that has never been possible before," Stephen Carpenter, a professor at the Center for Limnology at UW-Madison, said. "The main news is that agricultural production by clearing land in the tropics releases a lot of greenhouse gases per unit of food produced."
The tropics release nearly twice as much carbon to the atmosphere for each unit of land cleared compared to the world's temperate regions, another researcher said.
"Tropical forests store a tremendous amount of carbon, and when a forest is cleared, not only do you lose more carbon, but crop yields are not nearly as high as they are in temperate areas," Paul C. Est, a UW-Madison graduate student, said.
About 11 percent of tropical land is farmed, compared to 20 percent in temperate regions, but in the tropics the pressure to plant more land is growing fastest due to increasing human population, changing diets, food security concerns and a rising demand for the raw materials of biofuels, researchers say.