United Nations ? The world is turning to dust, with lands the size of Rhode Island becoming desert wasteland every year and the problem threatening to send millions of people fleeing to greener countries, the United Nations says.

One-third of the Earth’s surface is at risk, driving people into cities and destroying agriculture in vast swaths of Africa. Thirty-one percent of Spain is threatened, while China has lost 36,000 square miles to desert, an area the size of Indiana, since the 1950s.

This week the United Nations marks the 10th anniversary of the Convention to Combat Desertification, a plan aimed at stopping the phenomenon. Despite the efforts, the trend seems to be picking up speed — doubling its pace since the 1970s.

“It’s a creeping catastrophe,” said Michel Smitall, a spokesman for the U.N. secretariat that oversees the 1994 accord. “Entire parts of the world might become uninhabitable.”

Slash-and-burn agriculture, sloppy conservation, overtaxed water supplies and soaring populations are mostly to blame. But global warming is taking its toll, too.

The United Nations is holding a ceremony Thursday in Bonn, Germany, to mark World Day to Combat Desertification, and will have a meeting this month in Brazil to take stock of the problem.

The warning comes as a controversial movie, “The Day After Tomorrow” is whipping up interest in climate change, and as rivers and lakes dry up in the American West, giving Americans a taste of what’s to come elsewhere.

The United Nations says:

l From the mid-1990s to 2000, 1,374 square miles have turned into deserts each year — an area about the size of Rhode Island. That’s up from 840 square miles in the 1980s, and 624 square miles during the 1970s.

The desert encroaches onto fertile planting fields west of Yin Chuan, capital of Ningxia Hui Autonomous Region, in northwest China in this July 31, 1996, file photo. China has lost 36,000 square miles, an area the size of Indiana, to desert since the 1950s.

l By 2025, two-thirds of arable land in Africa will disappear, along with one-third of Asia’s and one-fifth of South America’s.

l Some 135 million people — equivalent to the populations of France and Germany combined — are at risk of being displaced.

Most at risk are dry regions on the edges of deserts — places like sub-Saharan Africa or the Gobi Desert in China, where people are already struggling to eke out a living from the land.