Importance of Wetlands
The Important Role of Wetlands on Our Landscape
"Wetlands protect water quality by trapping sediments and retaining excess nutrients and other pollutants such as heavy metals. These functions are especially important when a wetland is connected to groundwater or surface water sources (such as rivers and lakes) that are in turn used by humans for drinking, swimming, fishing, or other activities. These same functions are also critical for the fish and other wildlife that inhabit these waters. Wetlands help clean our air and drinking water, recharge ground water supplies and ease the effects of flooding and drought. They are also important habitat for wildlife and offer eco-tourism and recreational opportunities. Despite a growing awareness of their value, wetlands continue to be lost.
Sediments, nutrients, and toxic chemicals enter wetlands primarily by way of "runoff," a term used to describe the rain and storm-water that travels over land surfaces on its way to receiving waters. In urban areas, runoff washes over buildings and streets in industrial, commercial, and residential areas where it picks up pollutants and carries them to receiving waters. In rural areas, agricultural and forest practices can affect runoff. Where the runoff drains a freshly-plowed field or clear-cut area, it may carry too much sediment. Runoff may carry pesticides and fertilizers, if these have been applied to the land.
Sediments, which are particles of soil, settle into the gravel of streambeds and disrupt or prevent fish from spawning, and can smother fish eggs. Other pollutants -- notably heavy metals -- are often attached to sediments and present the potential for further water contamination. Wetlands remove these pollutants by trapping the sediments and holding them. The slow velocity of water in wetlands allows the sediments to settle to the bottom where wetland plants hold the accumulated sediments in place.
Runoff waters often carry nutrients that can cause water quality problems. An example of such an occurrence is an "algae bloom." Besides the aesthetic problems associated with algae blooms (a green, smelly slime) they result in low levels of oxygen in the water. This oxygen depletion can result in the death of fish and other aquatic life. Some algae release toxins that can kill pets and livestock when bloom conditions occur. Wetlands protect surface waters from the problems of nutrient overload by removing the excess nutrients, some of which are taken up and used by wetland plants, and some of which are converted to less harmful chemical forms in the soil.
Toxic chemicals reach surface waters in the same way as nutrients, and can cause disease, death, or other problems upon exposure to plants and animals (including humans). In a function similar to nutrient removal, wetlands trap and bury these chemicals or may even convert some of them to less harmful forms."
A 2010 Ducks Unlimited Canada research study shows 72 per cent of southern Ontario's large inland wetlands have been lost or converted to other land uses over the last 200 years and this loss continues. Extensive loss of wetland habitat throughout the Great Lakes basin has played a significant part in declining water quality in all five lakes.