courtesy Indur Goklany

In an article in today's New York Times titled, "In Niger, Trees and Crops Turn Back the Desert," Lydia Pollgren notes how property rights to trees growing on farmers' land have contributed to both economic growth, agricultural productivity and conservation in Niger at virtually no cost. She notes that :

In this dust-choked region, long seen as an increasingly barren wasteland decaying into desert, millions of trees are flourishing, thanks in part to poor farmers whose simple methods cost little or nothing at all...
[D]etailed satellite images and on-the-ground inventories of trees, have found that Niger, a place of persistent hunger and deprivation, has recently added millions of new trees and is now far greener than it was 30 years ago.
These gains, moreover, have come at a time when the population of Niger has exploded, confounding the conventional wisdom that population growth leads to the loss of trees and accelerates land degradation, scientists studying Niger say...
"The general picture of the Sahel is much less bleak than we tend to assume," said Chris P. Reij, a soil conservationist who has been working in the region for more than 30 years ... "Niger was for us an enormous surprise."

What contributed to the success? Apparently greater rainfall and property rights! As the article elaborates:

Another change was the way trees were regarded by law. From colonial times, all trees in Niger had been regarded as the property of the state, which gave farmers little incentive to protect them. Trees were chopped for firewood or construction without regard to the environmental costs. Government foresters were supposed to make sure the trees were properly managed, but there were not enough of them to police a country nearly twice the size of Texas. But over time, farmers began to regard the trees in their fields as their property, and in recent years the government has recognized the benefits of that outlook by allowing individuals to own trees. Farmers make money from the trees by selling branches, pods, fruit and bark. Because those sales are more lucrative over time than simply chopping down the tree for firewood, the farmers preserve them.