| 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
Features of Wetlands in the Wetland Regions of Canada
| 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. |
|
Source: P.D.N. Hebert. Canada's Aquatic Environments.
Habitats - Wetlands. Guelph, Ontario: University of Guelph, 2000. |
