Fencing off streams and wetlands from stock has many benefits. When livestock have free access to waterways it can cause stream banks to erode, releasing sediment into the water. Stock also pollute the water directly with their waste. Farmers who fence off streams and plant waterway margins with native shrubs improve the water quality, as the vegetation filters out nutrients and bacteria from farm runoff. The slowing of runoff also reduces flood peaks, which in turn reduces erosion of the stream bed. The overall improvement in water quality and cover along the stream margins improves the habitat for fish and bird life.