Streamside forests are complex ecosystems vital to the protection of our streams and rivers Streamside forests are crucial to the protection and enhancement of the water resources of the Eastern United States. They are extremely complex ecosystems that help provide optimum food and habitat for stream communities as well as being useful in mitigating or controlling nonpoint source pollution (NPS). Used as a component of an integrated management system including nutrient management and sediment and erosion control practices, streamside forests can produce a number of beneficial effects on the quality of water resources. Streamside forests can be effective in removing excess nutrients and sediment from surface runoff and shallow groundwater and in shading streams to optimize light and temperature conditions for aquatic plants and animals. Streamside forests also ameliorate the effects of some pesticides, and directly provide dissolved and particulate organic food needed to maintain high biological productivity and diversity in the adjoining stream.
Streamside forests are crucial to water resource protection.	Jeff Horan Maryland Dept. of Natural Resources

		Forested watersheds are the generally accepted benchmark of quality for water resources.
USDA Forest Service

	Deforestation associated with agricultural expansion has left our waters vulnerable to pollution from animal waste and fertilizer.
		USDA Soil and Conservation Service

Reference: 1985. America's Clean Water: The State's Evaluation of Progress.

		Many of America's waters have been rendered unfit for use.
USDA Soil and Conservation Service

The removal of streamside forests has adversely affected the vitality of our water resources In natural conditions, streamside forests protected most of the rivers and streams of our nation, but deforestation associated with agricultural and urban expansion has drastically reduced the extent of streambank protected by forest. The result has been an adverse effect on the quality of water and aquatic habitats. In many of our streams and estuaries, water is unfit for human consumption, industrial use or recreation. Shellfish and finfish production is also reduced. These problems are linked, in part, to contamination from nutrients, sediment, animal waste, and other pollutants associated with agricultural and urban runoff.

Continued Strengthening of the Clean Water Act Reflects the Public's Concern for Clean Water The Water Pollution Control Act of 1948 or "Clean Water Act" and its subsequent amendments through 1987 demonstrate strong congressional determination to improve the quality of our water resources. These laws have done much to clean up point source contaminants by requiring states to establish and enforce water quality standards, by requiring specifications and licensing for the discharge of effluents, and by funding the installation of municipal sewage treatment plants. As a result of the cleanup of concentrated pollution from specific sites, nonpoint source pollutants, which are typically dispersed in origin, have increased in relative importance and now account for more than 50% of the pollution in our nation's waters. Nonpoint source pollutants include sediment, nutrients, pesticides, animal wastes and other substances which enter our water supply as components of runoff and groundwater flow.

Streamside Forests Remove Pollutants in Several Ways Recent research has shown that streamside forests can: 1) improve the quality of water resources by removing or ameliorating the effects of pollutants in runoff and 2) increase the biological diversity and productivity of stream communities by improving habitat and adding to the organic food base. Streamside forests function, often simultaneously, as FILTERS, TRANSFORMERS, SINKS and SOURCES.

Excess Nitrogen and Phosphorous Spur Algal Growth, Deplete Oxygen and Kill Fish Aquatic plants, like their terrestrial counterparts, require nutrients to grow and reproduce. The growth of algae and other vegetation in water bodies is usually controlled by the nutrient whose supply is most limited. This concept, first described by Justis Liebig in 1840, is known as "Liebig's Law of the Minimum". Phosphorous is usually the limiting nutrient in brackish or freshwater, while nitrogen is usually the limiting nutrient in saltwater. When excess nutrients applied to the land in the form of manure or commercial fertilizer find their way into the water, blooms or overabundant growth of algae and other aquatic plants can result. Algal blooms at the surface can interfere with photosynthesis of submerged plants by blocking sunlight, causing them to die. When this happens, dissolved oxygen levels near the bottom drop abruptly because oxygen demand by decomposing bacteria is great while little or no oxygen is being produced by the dying plants. The problem is compounded when organisms which flourish in oxygen starved environments release hydrogen sulfide and methane. These substances are toxic to fish and other aquatic life. Excessive algal growth in estuaries can result in decline of Eelgrass and the loss of shellfish beds. Shellfish die and the beds fail to recolonize when thick layers of algae prevent animals such as oysters from pumping water through their bodies to provide adequate food and oxygen. Eelgrass, a submerged grass eaten by many waterfowl, is lost when floating algal mats and or phytoplankton in the water reduce light penetration and interfere with photosynthesis. Some species of fish, as well as other animals lower in the food chain, are very sensitive to low levels of oxygen or food and generally die. The loss of species simplifies the food chain of an ecosystem and makes it more vulnerable to further destruction.

Excess Nitrogen in Drinking Water is Detrimental to Children and Livestock Excess nitrogen, in surface and groundwater systems used for drinking water, is dangerous to the health of certain groups of people and animals. For example, infants less than six months old are particularly susceptible to harm because their stomachs are not acidic enough to prevent the growth of certain bacteria which convert nitrate to nitrite. High levels of nitrites can oxidize hemoglobin to form methanoglobin which is unable to carry oxygen. Brain damage or death by suffocation can result from this condition known as methemoglobinemia or blue baby syndrome. Pregnant cows can also suffer from the syndrome which usually results in death of the cow, calf or both. The allowable level of nitrogen in water for children six months of age or less is 10 ppm (10 mg/1) as nitrate nitrogen or 45 ppm (45 mg/1) as nitrate. Adults and older children can probably tolerate higher levels, but the standard is usually set at the more conservative level. Should groundwater become contaminated, nitrate removal at a community treatment plant is presently estimated to cost about $10 to $15/month for a family of three.

The Streamside Forest Removes Sediment and Sediment-Attached Phosphorus by Filtration The streamside forest functions as a FILTER by removing sediment and other suspended solids from surface runoff. Sediment is probably the most common and most easily recognized of the nonpoint source pollutants. Cropland erosion accounts for about 38% of the approximately 1.5 billion tons of sediment that reach the nation's waters each year. Pasture and range erosion accounts for another 26%.

Reference: 1989. Environmental Trends, Council on Environmental Quality.

		Sediment suspended in the water can reduce or block the penetration of sunlight, adversely affecting the growth and reproduction of beneficial aquatic plants. Sediment deposited on the stream bottom can interfere with the feeding and reproduction of bottom dwelling fish and aquatic insects, weakening the food chain. Large deposits of sediment can overfill stream channels and floodplains, greatly increasing the potential for flooding.

		Sediment is the most easily recognized of the nonpoint source pollutants.
USDA Soil Conservation Service

Streambank erosion also contributes to stream sediment load.

Several mechanisms of sediment removal are at work in the streamside forest. Some sediment settles out as the speed of the flow is reduced by the many obstructions encountered in the forest litter. Additional sediment is filtered out by the porous soil structure, vegetation and organic litter as the runoff flows over and into the floor of the streamside forest. Phosphorus is also reduced by the filtering action of the streamside forest because about 85% of available phosphorus is bonded to the small soil particles comprising the sediment. Approximately 4% of the phosphorus is attached to soil particles too small to be filtered by these processes resulting in a removal of about 80% of phosphorus by the riparian forest filter. The minor amount of ammonium which is bound to sediment can be filtered out in the same way. However, dissolved phosphorus and nitrate must be removed by either microbial or biochemical transformation processes.

		Reference: Maryland Department of Natural Resources
Reference: 1989. Environmental Trends, Council on Environmental Quality.