The recent extreme dust storms in Arizona and Texas have people wondering if another Dust Bowl, similar to the 1930s, could be in our future. Agroforestry, which combines planting trees and shrubs with crops, forages and livestock pasturing, had its beginnings in the United States in response to the Dust Bowl. The term came into widespread use in the 1970s. The land use systems and practices used in agroforestry may provide a solution to loss of soil in the form of dust. In addition, there are other benefits. Agroforestry can halt desertification, reclaim degraded land and help families have a secure food supply. Planting trees and shrubs in agricultural areas conserves soil, improves biodiversity, provides carbon storage to reduce greenhouse gases and improves water quality. Planting trees next to crops can increase crop yield. Profit on a cow-calf pair increases when agroforestry provides shelter to grazing livestock (M. Fisher, Agroforestry: A growing science seeks to boost its practice, CSA News, November 2011).
Although only decades old in the U.S., agroforestry has existed in Spain for 4,500 years and is used to shelter pastured livestock. Poor farmers in tropical and arid areas have been interplanting trees with crops (alley cropping) for centuries. In these areas, the trees become additional food and fuel wood sources.
Why do trees help improve crop yields, particularly in arid areas? Trees can reduce wind speed. They cool the air, allowing the plants below them to lose less water out their leaves (evapotranspiration). Soils dry out less quickly. Runoff is often eliminated in the presence of trees, and water infiltrates into the ground. Erosion and sediment loss drops significantly.
In Iowa, Red Fern Farm uses a multilevel approach, interplanting medicinal roots, livestock forage (grasses) and medicinal plants at the lowest level. At the next level are trees they cut for wood and, finally, the tallest level contains fruit trees including chestnut, walnuts, persimmons and paw paws on 20 acres of land.
While few of us have enough land to farm with agroforestry principles, we can integrate food production into our landscapes for more efficient land use. Instead of a simple shade tree, we can plant fruit trees. We can replace non-fruiting bushes with fruiting shrubs. Beautiful perennial and annual edibles could take the place of mere pretty landscape plants. As our fruit trees shelter our other food-producing plants, they also utilize water more productively.