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10 Advancements in Environmental Engineering


2
Agroforestry
This farm in Kenya keeps trees growing alongside crops to maintain an agriculturally productive landscape. ©Wendy Stone/Corbis
This farm in Kenya keeps trees growing alongside crops to maintain an agriculturally productive landscape. ©Wendy Stone/Corbis

Agroforestry is the simultaneous management of trees and shrubs with crops and/or livestock for more efficient, integrated and environmentally sustainable land use. Applied properly, it increases product diversity, agricultural production and soil and water quality and decreases erosion, pollution and susceptibility to harsh weather conditions. It can also be used to shelter wildlife, protect watersheds and manage carbon emissions more effectively. All of these can add up to greater income for farmers and a better environment.

Various agroforestry methods can be employed depending upon the available land and resources. One is alley cropping -- growing crops alongside rows of trees like oak, ash, walnut, pecan or other nut trees. The crops and nuts can be harvested and sold while the trees mature and continue to produce nuts. Another is forest farming, using canopies of trees to provide the right level of shade for crops like ferns, mushrooms and ginseng. These can also be sold before the trees are ready for harvesting. A third is the creation of riparian forest buffers -- groups of trees, shrubs and grasses are planted as a buffer to prevent pollution and erosion of banks and waterways. Similarly, trees and shrubs can be planted in configurations called windbreaks that shield crops from wind damage and erosion and protect animals from harm. Windbreaks can increase bee pollination and manage the spread of snow over crops or roads. Another agroforestry method is silvopasture, using trees to shelter livestock and the grasses and other plants they eat. In all cases, crops, animals and trees symbiotically coexist together, and the farmer can concentrate on harvesting whatever is ready at the time.

In some countries, governmental policies stifle these practices, partially because of disconnects between the agencies that deal with the different items involved. But there's increasing attention being given to agroforestry as a sustainable farming method. In the U.S., the 1990 Farm Bill led to the creation of the USDA National Agroforestry Center.