Agroforestry - growing crops or pasturing food animals near or among trees - has lots of advantages. Trees give protection from wind, help hold soil in place, help reduce runoff water loss, and their roots help enrich the soil with microorganisms. Deep tree roots capture leached nutrients. Tree leaf litter decays & enriches the soil. Trees offer habitat for birds & other natural predators of food crop insect pests, thus reducing the need for artificial insect control. Agroforestry has been used for centuries in many countries around the world. One source of more information: http://www.worldagroforestry.org/about/agroforestry-our-role