Hudson Plains Ecozone (CEC)

This article is about an ecozone. For the landform covering the same general region, see Hudson Bay Lowland.

The Hudson Plains Ecozone is a sparsely populated Canadian subarctic ecozone extending from the western coast of Quebec to the coast of Manitoba, encompassing all coastal areas of James Bay and those of southern Hudson Bay, stretching to about 50°N latitude. It includes the largest continuous wetland in the world. It covers nearly a quarter of Ontario's landmass, and 3.6% of Canada's total area, totalling approximately 369,000 square kilometres of land and 11,800 square kilometres of water. Its historical prominence is due to the harshness endured by pioneer explorers who established fortifications for Hudson's Bay Company, and as a result of regional wars between France and Britain. Today, it is primarily noted for the well-known Polar Bear Provincial Park, and to a lesser extent Wapusk National Park, as well as its vast wetlands which are used by migratory birds.

Geography

The Palaeozoic and Proterozoic sedimentary deposits overlaying the bedrock have formed into a wide and level plain characterised by raised beaches and river deltas, with an elevation rarely exceeding 120 m. The relatively flat land slopes gently toward the two bays, which act as a drainage basin for the region. However, the relatively poor drainage system has spurred the natural development of numerous wetlands. It is encircled by the Canadian Shield, with which it overlaps in a few areas to the east and west.

To its north is the cold Arctic Archipelago Marine ecozone, and to the south is the milder Boreal Shield. Hence, this ecozone is transitional, which is easily evident as it transforms from barren tundra in the north to open taiga forests in the south. These forests resemble those of the boreal zone, with sparser vegetation.

Thousands of depressions carved by retreating glaciers have become lakes and wetlands. The Hudson Plains is also noted for coastal marshes and extensive tidal flats, with tidal marshes along the coast of Hudson Bay. Belts of raised beaches are evident where rebound from glacier retreat is most prominent.

Climate

The ecozone has a subarctic climate which is significantly influenced by the adjacent marine area of Hudson Bay, which features cold and moisture-laden low-pressure systems. Frigid polar high-pressure air masses commonly reach the area. Typically cold, mean January temperatures are near −19°C, and mean July temperatures range between 12°C and 16°C. The region experiences moderate precipitation, between 400 mm to 700 mm annually. Summers are cool and relatively short, with prolonged daylight, while winters are very cold.

Flora and fauna

Referred to as an "insect-infested landscape of bog and fog", it teems with large insect populations that are a food source for migratory waterbirds. The Hudson Plains have become "notorious for their populations of biting insects". Vegetation is somewhat limited, with the northern areas abutting the Arctic Archipelago Marine being nearly treeless, whereas the southern extent, adjacent to the Boreal Shield, have open forest. Alder, willow, black spruce and tamarack are the most common plant species in the treed bogs and fens of the Hudson Plains, whereas sphagnum and shrubs such as crowberry and blueberry dominate the open bogs to the north, with white spruce appearing further south. Poorly drained areas produce dense sedge, moss and lichen cover.

The Hudson Plains also represent the southern extent of the polar bears yearly migratory route, which reaches the northwestern coast of Ontario. In autumn, polar bears migrate to the ice back forming along the coast of Hudson Bay. The bears then follow the Hudson Bay Coast toward Churchill, Manitoba. Mammals such as moose, woodland caribou and black bears are comfortable in this environment, but smaller mammals are more common, including muskrats, weasels, Arctic foxes, martens, and fishers.

The adjacent marine ecozone of the Arctic Archipelago Marine supports mammal populations of walrus and bearded, harbour and ringed seals.

Millions of migratory shorebirds stage and nest in multiple areas of the Hudson Plains, particularly in three areas within Southern James Bay: Akimiski Island, and the migratory bird sanctuaries at Hannah Bay and the mouth of the Moose River. Representative species include the snow goose, Canada goose, king eider, swan, loon, gyrfalcon, and peregrine falcon.