Region

Three grassland types occur in the Canadian prairies: tallgrass prairie, mixed prairie, and fescue prairie. Each has a unique geographic distribution and characteristic mix of plant species. All but a fraction of one percent of the tallgrass prairie has been converted to cropland. What remains occurs on the 6,000 square kilometer plain centered in the Red River Valley in Manitoba. Mixed prairie is more common and is part of the dry interior plains that extend from Canada south to the US state of Texas. More than half of the remaining native grassland in the Canadian prairies is mixed. Though widespread in southern Saskatchewan and southeastern Alberta, due to extensive cattle grazing, it is estimated that only 24 percent of the original mixed prairie grassland remains. Fescue prairie occurs in the moister regions, occupying the northern extent of the prairies in central and southwestern Alberta and west central Saskatchewan.

The southern Canadian prairies, supporting brown and black soil types, are semi-arid and highly prone to frequent and severe droughts. The region known as Palliser's Triangle is so arid that farming has never been successful there without government help and irrigation. The zones around the cities of Regina and immediately east of Calgary are also very dry. In an average year, southern Saskatchewan receives between 300 mm and 510 mm of precipitation, with the majority falling between April and June. Frost from October to March limits the growing season.

The eastern section of the Canadian prairies in Manitoba, is well watered with several large lakes such as Lake Winnipeg, and several large rivers. The area also gets reasonable amounts of precipitation. The middle sections of Alberta and Saskatchewan are also wetter than the south and have better farmland, despite having a shorter growing season. The areas around Edmonton and Saskatoon are especially notable as good crop land. However, Edmonton and Saskatoon both lie far enough north that they are surrounded by aspen parkland rather than fescue prairie.

Further north, the area becomes too cold for most agriculture and is dominated by boreal forest. The Peace Region in northwestern Alberta is an exception, however. It lies north of the 55th Parallel and is warm and dry enough to support extensive farming. Like the area around Edmonton, aspen parkland is a major biome in the Peace Region. The long daylight hours in this region during the summer are an asset despite having an even shorter growing season than central Alberta. In fact, agriculture plays a major economic role in the Peace Region.

Flora

The shift from grassland to cropland in the Prairies has increased losses of organic matter and plant nutrients from the soil. It is estimated that the original organic matter levels have fallen by 40 to 50%. Over the past century the ecozone has been radically transformed and only a small fraction remains in its native state. Perhaps less than 1% of the Tall-grass Prairie, 18% of the Short-grass Prairie, and 24% of the Mixed-grass Prairie remain. Today, the Tall-grass Prairie region of Manitoba is almost completely cultivated. Over 90% has been converted to crops or drastically changed by grazing and haying. And 75% of the Mixed-grass Prairie and Aspen Parkland has been converted to cropland or seeded to non-native forage species.

The Aspen Parkland, the northern transition zone to the Boreal Forest, has expanded south into former grasslands since settlement put an end to prairie fires. The natural vegetation is generally dominated by Spear Grass, Wheat Grass, and Blue Grama Grass. Sagebrush is abundant. Local saline areas feature Alkali Grass, Wild Barley, Greasewood, Red Samphire, and Sea Blite. Drier sites in the southwest are home to yellow Prickly Pear Cactus.

The Short-grass Prairie occupies the driest southerly arc of the region, where brown and dark brown soils are dominant. The northern edge of the ecozone is dotted with groves of Trembling Aspen and Balsam Poplar and characterized by black Chernozemic soils. The most productive soils in the region are the black, dark grey, and dark brown soils of the Aspen Parkland and the Tall-grass and Mixed-grass Prairie.

Lakes and wetland areas are rich in vegetation. Depending upon rainfall, there are between 1.6 and 7.1 million wetlands in this ecozone, and lakes cover 7 800 square kilometres. The greatest number of wetlands occur along the subhumid Northern Grasslands and adjacent Aspen Parkland, where they make up half the land area. However, lake and wetland areas are under threat. Virtually every major natural water system has been extensively modified and developed for hydro and thermal power generation, irrigation, flood protection, and water management. Agriculture and urbanization have cut the number of wetlands in half.

Few deciduous trees and shrubs grow in the ecozone except in the eastern regions, sheltered locations along waterways or at upper elevations. The east is characterized by Trembling Aspen and shrubs, whereas the southwest displays a mixed montane-type open forest of Lodgepole Pine. Southwest Manitoba contains a forest reserve that occupies most of the higher elevations of Turtle Mountain.

Fauna

The Prairies Ecozone provides habitat for many animal species. Intermittent sloughs and ponds on the plains offer major breeding, staging, and nesting grounds for migratory waterfowl using the Central North American flyway. More than half of all North American ducks are born in Prairies Ecozone wetlands. River valleys also offer sheltered habitats important to wildlife, especially during the harsh winters. The Prairies offer unique habitat for the Black-tailed Prairie Dog, while its southern region is home to the Short-horned Lizard and Western Rattlesnake. Manitoba provides habitat for Black Bear, Moose, Sharp-tailed Grouse, Beaver, and Red Fox. Also present are various species of frog and toad. Local fish include Walleye, Lake Whitefish, and Northern Pike.

Considering its area and population, the Prairies Ecozone has a disproportionate number of threatened and endangered wildlife species. At least four vertebrate species -- the Plains Grizzly, Swift Fox, Black-footed Ferret, and Greater Prairie Chicken -- have disappeared from the area. The Peregrine Falcon, Mountain Plover, Eskimo Curlew, Piping Plover, Burrowing Owl, and Whooping Crane are all endangered.

Agriculture has probably had the greatest impact on the ecozone. By replacing natural grasslands with crops, draining wetlands, and destabilizing natural chemical balances in the soil with pesticides, the number and range of wildlife species has changed dramatically. As well, competing, non-native species have been introduced.

Within aquatic ecosystems, high-value fish stocks are under pressure, particularly Walleye and Sauger, which are prized by commercial and recreational fishers. Stocks have been reduced through overfishing and are sensitive to water quality in the controlled-drainage systems as well as to natural fluctuations. For example, contaminants from the widespread use of pesticides have damaged fish habitat.