Chesapeake Bay - Forests are critical to improving the water quality of the Bay

Streamside forests critical to wildlife, water quality
Bay Naturalist / By Kathy Reshetiloff - Bay Journal

When European colonists first arrived in the Chesapeake Bay region, an estimated 90-95 percent of the watershed was forested. Or put another way, forests lined both sides of almost every stream, creek and river draining into the Chesapeake Bay.

Because of their fertile soil, many riparian forests were cleared for agriculture. As more people moved into the region, more land was cleared to make room for suburban and urban developments. Today, only about 58 percent of the watershed is forested. A little more than half of all waterways in the watershed still have riparian forests of 100 feet or more bordering them on both sides.

These streamside wooded areas are critical to improving the water quality of local waterways and the Chesapeake Bay. As a transition area between aquatic and terrestrial environments, riparian forests act as buffers, intercepting rainwater and runoff that can contain pollutants such as sediment, nutrients and chemicals. Rain infiltration rates are 10-15 percent higher in forests than turf grass fields and 40 percent higher than plowed fields.

Nitrogen and phosphorus are nutrients that are essential for the growth of plants. But an overabundance of these nutrients in rivers and the Chesapeake Bay causes a rapid growth of algae that blocks sunlight needed by Chesapeake Bay underwater grasses. The decomposition of this overabundance of algae also uses up large amounts of oxygen needed by fish and other aquatic organisms.

Streamside forests remove nitrogen through plant growth. Bacteria in the forest floor convert nitrate to nitrogen gas that is then released harmlessly into the atmosphere.

Water runoff often contains large amounts of sediment that clouds the water and covers critical habitat. As runoff moves through a forest, the physical structure of the vegetation filters out soil particles so that the forests act as a sediment trap. Phosphorus, which is often attached to soil particles, is also filtered out with the sediment.

Trees growing alongside streams and rivers also hold soil in place with their roots, stabilizing stream banks. They reduce flooding by slowing the erosive force of rain and floodwaters. Many riparian forests also contain wetlands, which can temporarily hold floodwater and release it slowly over time.

Fish, crayfish, aquatic insects and other aquatic organisms derive benefits from riparian forests.

Streamside vegetation helps to control water temperature. Without shading, temperatures might be too high in spring and summer. This is especially important for healthy fish populations as temperature is one of the major factors controlling fish spawning. Warmer water also retains less oxygen and elevated water temperatures can accelerate algae growth.

Riparian forests contribute to the food cycle in a waterway. Plant material that falls into the water or is washed in by rains provides a source of food for aquatic insects, crayfish and other invertebrates which, in turn, are important food for small fish. Minnows, aquatic insects and insects that fall into waterways provide food for larger game fish.

Many other types of wildlife depend on a forest for food, cover, nests and nursery habitat. Bears, deer, foxes, raccoons, beavers, snakes and turtles are just a few of the animals that can be found in riparian forests.

Temporary pools that form in these areas in late winter and spring are important breeding areas for frogs, toads and salamanders. The unbroken riparian forests also create protective pathways through which wildlife can move. Forests and forest corridors are especially critical for migrating songbirds.

People regularly use riparian forests for hunting, fishing, nature study, bird watching camping and hiking. With the loss of these forests, we also lose the functions they provide such as reducing nonpoint source pollution and erosion, protecting adjacent land and water from flood damage, providing food and habitat for fish and other wildlife and providing recreational opportunities for people.

Kathryn Reshetiloff is with the U.S. Fish and Wildlife Service’s Chesapeake Bay Field Office in Annapolis.

Chesapeake Bay Article from:
Bay Journal - March 2011

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