Trees prevent soil erosion, enhance soil fertility and maintain soil moisture. In Algeria, for example, trees are used to stabilize sand dunes and arrest desertification. Deep-reaching tree roots can help mobilize nutrients far below ground level for use by food crops. Windbreaks and shelterbelts protect crops from drying, damaging winds. In New Guinea, shelterbelts have significantly increased grain production.
Trees also provide farmers with materials for fence posts, poles and farm implements.
Nearly 240 million pastoralists around the world depend mainly on tree fodder to feed their animals. In Costa Rica, dairy farmers retain scattered alder trees in their pastures because the trees improve the forage quality of the grass, resulting in greater milk production. Trees provide shade for livestock, important to their health and productivity in hot, dry areas. Of growing importance is the role forests play as storehouses of biodiversity, potentially very important in future crop breeding and pest and disease management programs. Forests also have significant links with inland and marine fisheries.