Water sources: wetlands
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Wetlands are submerged or permeated by water -- either permanently or temporarily -- and are characterized by plants adapted to saturated soil conditions. Wetlands include fresh and salt water marshes, wooded swamps, bogs, seasonally flooded forest, sloughs -- any land area that can keep water long enough to let wetland plants and soils develop.
They are the only ecosystem designated for conservation by international convention. They have been recognized as particularly useful areas because:
- they absorb the impact of hydrologic events such as large waves or floods;
- they filter sediments and toxic substances;
- they supply food and essential habitat for many species of fish, shellfish, shorebirds, waterfowl, and furbearing mammals;
- they also provide products for food (wild rice, cranberries, fish, wildfowl), energy (peat, wood, charcoal), and building material (lumber); and
- they are valuable recreational areas for activities such as hunting, fishing, and birdwatching.
In the past, wetlands were considered wasteland, and many of southern Canada's wetlands were drained or filled in so that they could be farmed or built upon. Recently the value of wetlands has been recognized and efforts have been made to protect these ecosystems. However, they are still disappearing under the pressure of human activity, and are being threatened by air pollution and climate change.
Options to prevent further loss of wetlands include the following:
- adding sediment to coastal wetlands to keep up with rising sea levels;
- planting grasses to protect coastal sands from erosion;
- building dikes or barrier islands;
- controlling water levels artificially; and
- developing a national policy of protection.
Wetlands cover about 13% of the land area of Canada. They were once abundantly distributed throughout the country. Recently, however, wetlands have become an increasingly scarce resource in settled areas of the country. Throughout Canada, wetlands have been adversely affected by land use practices that have resulted in vegetation destruction, nutrient and toxic loading, sedimentation, and altered flow regimes. For example, in southern Ontario, 68% of the original wetlands have been converted from their natural state to support alternative uses such as agriculture and housing. Similarly, only about 25% of the original wetlands of the "pothole" region of southwestern Manitoba remain in existence. In the North, however, most of the wetlands are intact.
The Atlas of Canada map of wetlands shows their extent and also specific wetlands of particular importance.
Wetlands are important to species from many familiar classes of animals, as well as to less commonly known creatures.
Every drop of water contains microscopic zooplankton, which are a vital component of the food chain. The water's surface and the wetland bottom are covered with insect eggs, larvae, and nymphs. Members of the fish, amphibian, and reptile groups are all dependent on the habitat provided by wetlands. Numerous bird and mammal species make extensive use of the water and its adjacent shores. These species can be important to humans economically or as indicators of environmental health.
Food and shelter are the primary requirements of life. Wetlands provide these functions for many species of animals that either live permanently within the wetland or visit periodically. Almost every part of a wetland, from the bottom up, is important to wildlife in some way. Frogs bury themselves in the muddy substrate to survive the winter, and some insects use bottom debris to form a protective covering. Fish swim and feed in wetlands, often eating the eggs of insects that have been deposited in the water. Wetland vegetation provides nesting materials and support structures to several bird species and is a major source of food to mammals, even those as large as moose. Small mammals use the lush vegetation at the edge of wetlands for cover and as a source of food, and they themselves are a food source for birds of prey. Each species has adapted to using the wetland and its surrounding area in a particular way.
As a frontier-type ecosystem, wetlands are particularly vulnerable to climatic variation and extreme events. Many wetlands, especially coastal ones, are unstable to start with, and are easily or frequently changed by erosion, flooding, or the invasion of salt water.
But water supply is the main concern. In arid and semi-arid areas, the occurrence of hotter, drier summers and the increased use of water for irrigation could reduce the supply of water for wetlands, either directly or indirectly (through the effect on the water table), or both. A lower volume of water would increase the concentrations of the pollutants that tend to settle in wetlands (agricultural chemicals, naturally occurring salts, atmospheric pollutants).
Small changes in temperature or water supply could have significant effects on wetland biota. A rise in temperature could allow an undesirable plant species (purple loosestrife, for example) to expand northward. High temperatures and low concentrations of oxygen favour the growth of the botulism bacterium. A change in the seasonality of precipitation could harm plants or animals whose life cycles require certain amounts of water at specific times of the year. Such a change could cause a decline in a plant on which waterfowl depend.
See also: Water and Climate Change section
Wetlands often have very close connections with the groundwater system. Some wetlands, for example, potholes in higher ground, may serve as important groundwater recharge areas. Others, especially those in low-lying areas, may be the receptors for significant amounts of groundwater discharge. In addition, if the underlying groundwater is contaminated, detrimental consequences will be felt by the wildlife and all other resources dependent on that wetland.
See also: Groundwater section
Our remaining wetlands can be protected through conservation programs. Wetland conservation encompasses the protection, enhancement, and use of wetland resources according to principles that will assure their highest long-term social, economic, and ecological benefits. It is recognized that some wetlands should be protected and managed in their natural state; some actively managed to allow sustained, appropriate use of wetland renewable resources; and some developed for their non-renewable resource values.
A significant program that aims at protecting our remaining wetlands is the North American Waterfowl Management Plan (NAWMP). In 1986, the governments of Canada and the United States signed the plan in reaction to the sharp decline in waterfowl populations associated with the destruction of their habitat. They were joined by Mexico in 1993.
The plan itself outlines the scope of the work to be done on a continental basis and provides broad guidelines for habitat protection and management actions. Many partners -- from federal and provincial or state governments to nongovernmental organizations and landowners -- representing various interests, work in partnership to achieve the NAWMP's goal to restore, protect, and enhance wetland habitat for the benefit of waterfowl, biodiversity, and humans.
Additional information on this program is available on the North American Waterfowl Management Plan Web site.
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