Clearing tropical forests for farmland is bad for the climate – no surprises there. But now we’ve learned that it’s also an inefficient way to feed people.

Paul West of the University of Wisconsin-Madison and colleagues worked out the potential yields of 175 different crops if they were planted in different parts of the world.

Then they estimated how much carbon would be released into the atmosphere by clearing these areas of wild plants.

“In the tropics, clearing a hectare of land releases twice as much carbon as in the temperate zones, and only produces half as much food,” says West.


“If we want to balance increasing food production and decreasing carbon emissions, we should emphasise increasing crop production on existing lands.”

Trouble in the tropics

“Continued expansion of croplands into tropical forests results in a lose-lose situation for growers and our climate system,” agrees Gregory Asner of Stanford University in California, who was not involved in the study.

However, he warns that boosting yields on existing lands can cause other problems, such as nitrogen pollution from fertiliser run-off. “We need to take such unintended consequences into consideration as well,” he says.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1011078107