Wetlands

Wetlands are permanently or temporarily submerged or permeated by water, and 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);
• they are valuable recreational areas for activities such as hunting, fishing, and birdwatching;

As a frontier-type ecosystem, wetlands are particularly vulnerable to climatic variation and extreme events. Many, 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.

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 now are threatened by air pollution and climate change as well.

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;
• developing a national policy of protection.

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