As the stream influences the land, so the land influences the stream in profound ways. The vegetation that lines the stream, called the riparian zone, is of particular importance. This canopy of shrubs and trees provides cooling shade as well as falling leaves and insects that are food for other aquatic insects, crayfish, and salmon. Branches and trunks of fallen trees slow the water, form eddies and pools, trap sediment and detritus, and shelter salmon and trout. Roots anchor streambanks, holding the soil.
Large roots stretch to the stream, providing shelter.
Loss of this vegetation is disastrous for a stream and especially for salmon . In the Northwest, salmon swim at the center of the stream ecosystem, linking the land with the sea. Born and reared in the clear, cold waters of our rivers and streams, most juvenile salmon species feed on aquatic insects - mayflies, stoneflies, caddisflies, and others. These insects feed upon the detritus of decaying leaves, wood, and other stream life. The decayed carcasses of adult salmon returned from the ocean to spawn and die are transformed into nutrients for the stream and food for their own offspring.