Friday, January 4, 2008

Life in Our Streams: A Green World

Vegetation along rivers and streams, called riparian vegetation, plays an important part in maintaining and improving the quality of our rivers and streams. The type, density and width of riparian vegetation provide a crucial link between terrestrial and stream ecosystems.

Native vegetation along the streambank provides food and shelter, while also providing a corridor for the movement of wildlife. Riparian vegetation provides vegetable matter, which breaks down and provides food for aquatic invertebrates. Shade from riparian vegetation helps maintain cool water temperatures in pools. In addition, fallen branches, large woody debris and aquatic plants provide habitat for fish and invertebrates.

Riparian vegetation is important in the prevention of stream bank erosion. Vegetation binds soil and and creates a “roughness” that reduces stream flow rates, particularly during floods. Vegetation at the base of riverbanks is especially important to riverbank stability, particularly on outside bends of meanders and on other banks where flow is deflected.Vegetated riparian zones maintain water quality by filtering sediment and nutrients, and reducing the amounts of water entering a water course. Any vegetation that provides a dense cover at ground level will be an effective filter. Riparian vegetation of course, has an inherent aesthetic and intrinsic worth that is difficult to value in monetary terms.
A wetland with different types of plants.

Wetlands are very productive ecosystems and can be thought of as “biological supermarkets.” Wetlands provide large amounts of food, which attract many different animal species. In addition to being “biological supermarkets” for other animals, wetlands produce a number of natural products used by humans, including fish and shellfish, cranberries, timber, wild rice, blueberries, as well as medicines that are extracted from wetlands soils and plants.

There are several types of wetland plants depending on where they live in the wetland:
Emergent plants are those that, although rooted under the water, emerge through the water’s surface (eg. sedges)
Submerged plants are those that stay submerged in the water column (eg. bladderwort)
Floating plants are those which live entirely on the water’s surface (eg. duckweed)

Wetland plants that require water and proper hydric soils at all times are termed “Obligates”. Those that are a little more forgiving in their environmental requirements are termed “Facultative”. Often, both can be found in a wetland.

Wetlands also absorb and retain stormwater helping to slow flooding. Wetlands are also useful in filtering out pollutants from Abandoned Mine Drainage (AMD). Long a part of passive treatment technology, wetlands can capture and retain metals from AMD that would otherwise settle out in a stream.

For more information:

The Value of Wetlands
from the World Wildlife Fund

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