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Wetlands
Abstract
Wetlands are lands permanently or temporarily submerged or permeated by water, and characterized by plants adapted to saturated-soil conditions. Wetlands are the only ecosystem designated for conservation by international convention because they absorb the impact of hydrologic events, filter sediments and toxic substances, supply food and essential habitat for many species, provide products for food, energy, and building material, and are valuable recreational areas. Some wetlands help recharge groundwater, while others receive groundwater discharge. Wetlands are vulnerable to climatic variations and extreme events. Wetlands occur across most of Canada. Their location usually depends on local factors of drainage, topography, and surface material.
Wetlands are water areas characterized by relatively shallow water. These areas fill an extremely important role in ecology. It is important for Canadians to be aware of wetlands for this reason, but also because Canada has one of the largest areas in the world of wetlands.
This map shows their extent and also specific wetlands of particular importance. The notes below explain the nature and importance of wetlands, then discuss the nature of wetlands across Canada.
What are wetlands?
Wetlands are lands 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 and peatlands - any area of relatively shallow water that can keep water long enough (and still enough) to let wetland plants and soils develop.
Wetlands are the only ecosystem designated for conservation by international convention. Wetlands have been recognized as particularly useful areas because they:
- absorb the impact of hydrologic events such as large waves or floods
- filter sediments and toxic substances
- supply food and essential habitat for many species of fish, shellfish, shorebirds, waterfowl and mammals
- provide products for food (wild rice, cranberries, fish, wildfowl), energy (peat, wood, charcoal) and building material (lumber)
- are valuable recreational areas for activities such as hunting, fishing, and birdwatching
Some wetlands help recharge groundwater, while others receive groundwater discharge. Wetlands are particularly vulnerable to climatic variation and extreme events. Many, especially coastal wetlands, are unstable to begin with, and are easily or frequently altered by erosion, flooding, or the invasion of salt water, or by many specifically human-caused activity such as dredging or constructing buildings.
In arid and semi-arid areas, the occurrence of hot dry summers and the increased use of water for irrigation can reduce the supply of water for wetlands either directly, or indirectly (through the reduction's effect on the water table). A lower volume of water can increase the concentrations of the pollutants that will tend to settle in wetlands (such as agricultural chemical residues, naturally-occurring salts, and atmospheric pollutants). Any tendencies to hotter, dryer climates in future will aggravate these tendencies.
Distribution of Wetlands
Wetlands occur across most of Canada. Their location usually depends on local factors of drainage, topography and surface materials. At a national scale, the distribution of wetlands is best explained by examining the map along with a layer showing geological provinces. It shows that wetlands are most common in the platform (flat-lying) areas, particularly in the Interior Platform areas just south and west of the Shield's southern border, and in the Hudson Bay Lowlands lying to the south of Hudson and James bays. Most parts of the Shield have wetlands, but these are scattered and result from localized factors of terrain and soils.
The types of wetlands across Canada are described in more detail by examining the main features of Canada's wetlands regions in Table 1.
Table 1. Features of Wetlands in the Wetland Regions of Canada
| Region | Main Features |
|---|---|
| Arctic | Five percent of the land area is covered by wetlands. |
| This region contains 20% of all Canada's wetlands. | |
| Permafrost plays an important role in wetland development by prohibiting internal drainage and concentrating available water at the surface. | |
| Subarctic | Thirty percent of the region is covered by wetland habitats. |
| The interaction of excess water, severe climate, and discontinuous permafrost produce distinctive wetland forms. | |
| Part of this region, the Hudson Bay Lowlands, covers an area larger than Great Britain. | |
| Salt marshes constitute 85 to 90% of the Hudson Bay Lowland | |
| Boreal | On average, 20% of the land in the Boreal wetland region is covered by wetlands. |
| Bogs and fens are common. | |
| Coniferous and hardwood swamps are prevalent in the southern part of this region. | |
| Delta marshes are common around large lakes and rivers, notably the Slave River delta (which is found in Great Slave Lake), and the Peace-Athabasca delta (located just west of Lake Athabasca). | |
| There are over 100 000 beaver ponds in the Boreal Region, covering 5 to 10% of its total area. | |
| Prairie | Fifteen to twenty-five percent of the Prairie Region is wetland. |
| Common wetland forms in this area include freshwater marshes, shallow open waters and saline marshes and individual pothole marshes. | |
| Half of the migratory birds on the continent pass through this region and use its wetlands. | |
| Temperate | Five to fifteen percent of this region is covered by wetlands. |
| Common wetland forms are hardwood tree swamps, extensive freshwater marshes, and saline marshes. | |
| Ninety to ninety-five percent of wetlands along the Lakes Erie and Ontario shores have been destroyed to enable urban development and agricultural production. | |
| Oceanic | Wetlands cover less than five percent of the Pacific part of this region, but there is a variety of wetland types, including coastal marshes, forested swamps, and fens. |
| Wetlands in the Atlantic part of this region are generally small. These wetlands feature coastal salt marshes behind barrier beaches and in protected bays, as well as bogs, fens, and forested swamps. | |
| Mountain | Note that this region is in two widely-separated parts: most is in the Western Cordillera, but a small part is in the Torngat Mountains of eastern Canada. |
| Common types of wetlands in both parts are floodplain marshes, potholes and shallow basin marshes in valley bottoms. The estuarine wetlands in the Fraser River Delta support the highest densities of over-wintering waterfowl, shorebirds, and birds of prey anywhere in Canada. |
Other Maps in this Series:
- Drainage Patterns Map | Read about this map
- Glaciers and Icefields Map | Read about this map
- Groundwater Map | Read about this map
