From the Chesapeake Bay through the agricultural fields of the Midwest to the forests of the Pacific Northwest, research has increasingly linked riparian forests with improved stream water quality and habitat. Riparian areas are a transitional area between the edge of the water and adjacent land uses. In addition, the roots that anchor the trees can remove up to 90 percent of the nitrogen moving through shallow groundwater before it enters the streams. While the Bay states have made progress in reducing the amount of phosphorus entering the Chesapeake, nitrogen has proven more difficult to control. The Bay states have a goal of reducing the amount of nitrogen and phosphorus entering the Chesapeake 40 percent from 1985 levels by the turn of the century.
Excess nutrients cause algae blooms, which degrade water quality in the Bay.
Forest buffers not only remove nutrients, their roots stabilize streambanks, protecting them from erosion and keeping sediment from clouding the water. Besides protecting water quality, trees improve aquatic habitat for fish and other species. Their leaves shade the streams, helping to protect their aquatic species from sharp fluctuations in temperature. Falling leaves provide the food that makes up the base of the aquatic food web. Roots and fallen tree limbs and trunks also help to form pools and riffles that create the varied habitats needed to support a healthy and diverse stream community.