Some research also shows that cattle farmers can improve their income by introducing trees, both by selling timber and by cooling cows in the shade.

And trees in general help the environment by absorbing greenhouse gases and by cleaning up polluted water — countering some of the effects of large-scale agriculture.

“The biggest problem with food production is environmental degradation,” said Gene Garrett, an emeritus professor of forestry and former director of the Center for Agroforestry at the University of Missouri.

Properly placed belts of trees and other vegetation along streams can filter out 95 percent of the soil sediment that washes off farm fields, studies show, and up to 80 percent of phosphate and nitrogen that runs off.

While the idea of farming with trees is being reborn in the United States, it is not new. It got its start here in the Dust Bowl era, when trees were planted in shelter belts to stop severe wind erosion, Mr. Mason said. And around the world, agroforestry goes back centuries. “Many generations have been on the land,” said Jill M. Belsky, a professor of rural and environmental sociology at the University of Montana who has studied forest farms. “They have deep ecological knowledge and many cycles of these seasons.

“For example, they taste the soil and say, ‘We need a few more chickens in here’ ” for fertilizer.

Elsewhere, “working” trees are being used to replenish eroded or desert landscapes. A program in Niger has greened millions of acres in the last 20 years.

There are several approaches to agroforestry. Grazing livestock under a canopy of trees is called silvo-pasture, for instance. In alley cropping, an ancient technique that is becoming more common in the United States, rows of commercially valuable hardwood trees like oak are alternated with rows of corn, wheat or grasses for biofuel.