Land degradation, such as a spread of deserts in parts of Africa, costs the world economy trillions of dollars a year and may drive tens of millions of people from their homes, a U.N.-backed study said on Tuesday.
Worldwide, about 52 percent of farmland is already damaged, according to the report by The Economics of Land Degradation (ELD), compiled by 30 research groups around the world.
It estimated that land degradation worldwide cost between $6.3 trillion and $10.6 trillion a year in lost benefits such as production of food, timber, medicines, fresh water, cycling of nutrients or absorption of greenhouse gases.
"One third of the world is vulnerable to land degradation; one third of Africa is threatened by desertification," it said.
Such degradation, including from clearance of tropical forests, pollution and over-grazing "can also lead to transboundary migration, and eventually create regional conflicts", it said.
The report cited a 2012 U.N. finding that up to 50 million people could be forced to seek new homes and livelihoods within a decade because of desertification.
In May, a study in the U.S. journal Proceedings of the National Academy of Sciences highlighted the link between drought, man-made climate change and conflict in Syria.
Much of the estimated lost trillions of dollars from land degradation in Tuesday's study falls outside conventional measures of gross domestic product - such as "free" pollination by insects or water purification by forests.
PHOTO: Residents walk on sand dunes in the Libyan desert oasis town of Ghadames April 19, 2013.
CREDIT: REUTERS/ISMAIL ZITOUNY.