Hudson Bay lowlands
The Hudson Bay Lowlands, located in Canada, represent the largest wetland area in North America, situated between the Canadian Shield and the shores of Hudson and James Bays. This expansive region spans parts of Manitoba, Ontario, and Quebec, acting as a transition zone between the boreal forest to the south and the Arctic tundra to the north. The unique landscape features various lowland and wetland types, including muskegs and fens, shaped by the remnants of glacial activity from the Pleistocene era. The area is characterized by diverse flora, with dominant species like black spruce and a variety of shrubs and mosses thriving in its nutrient-poor conditions.
The Hudson Bay Lowlands are currently experiencing significant environmental changes driven by climate change and geological processes like isostatic rebound, where the land rises as it rebounds from the pressure of ancient glaciers. These changes are leading to shifts in vegetation patterns and impacting local wildlife, including migratory species like the snow goose and amphibians like the wood frog. As temperatures rise and precipitation patterns shift, the delicate balance of this biodiverse region faces increased risks, making it a critical area for ecological study and conservation efforts.
Hudson Bay lowlands
Category: Forest Biomes.
Geographic Location: Canada.
Summary: The Hudson Bay Lowlands biome is the largest wetlands in North America, but the region faces significant changes as a result of isostatic rebound and climate change.
The Hudson Bay lowlands are the largest wetland area in North America, covering a vast expanse of Canada between the Canadian Shield and the southern shores of Hudson and James Bays. Encompassing parts of the Canadian provinces of Manitoba, Ontario, and Quebec, the lowlands are along the ecotone (overlap) between the boreal forest to the south and Arctic tundra to the north. The area faces significant change, however, from the effects of climate change as well as isostatic rebound (rising ground elevation) of a landscape once burdened by the fantastic weight of continental, ice-age glaciers.
The location of Hudson Bay and the lowlands to its southwest and south correspond with the approximate center of the Laurentide Ice Sheet—the massive ice load that covered North America during the Pleistocene period, before it retreated and melted some 20,000 years ago. The massive weight of that ice, which was as much as two miles thick, compressed the ground below, allowing incursion of salt water in areas far beyond the current shores of Hudson Bay. In addition, the ice scoured the ground beneath it, effectively bulldozing or filling in the original drainage network and ensuring, because of that disrupted drainage, that large swaths of the region would remain wet and bogged down after the glaciers retreated.
The landforms left behind include gravel ridges and hills—usually derived from glacial deposits—raised beaches, occasional rocky outcrops, permafrost hummocks, and extensive lowlands filled with glacial or marine sediments. Upland areas are often dominated by boreal forest vegetation, in particular white spruce—one of the dominant species of the North American boreal forest—with balsam fir, quaking aspen, balsam poplar, and paper birch. Important plant associates include dogwood, willow, lingonberry, bearberry, twinflower, miterwort, false toadflax, wintergreen, or mosses such as Hylocomium or Pleurozium. Stands of black spruce and jack pine may also be important components of the forests of upland sites.
Lowland and Wetland Types
The type of lowland sites are influenced in large part by site conditions. Tundra, dominated by shrubs such as blueberry, lingonberry, bearberry, and lichens such as Cladonia, occurs in relatively well-drained sites in a strip along the Hudson and James Bay coasts. On poorly drained sites, bogs develop under acidic conditions, and fens develop under neutral or alkaline conditions. Both develop in poorly drained areas, where organic matter may accumulate over time. The Hudson Bay Lowlands biome features an abundance of both.
A common type of wetland in the Hudson Bay Lowlands is the muskeg. The nutrient-deficient substrate often supports an open stand of black spruce, but the muskegs are dominated by mosses such as Sphagnum, with a handful of shrubs such as Labrador tea, dwarf willow, and dwarf birch. Another type of muskeg is dominated by Cladonia lichens, with shrubs such as Labrador tea and blueberry.
While raised bogs appear to be higher in elevation than the surrounding tundra, their elevation results from accumulation of peat in areas that were once lower in elevation than the surrounding landscape. The sites are poorly drained, much like a raised wetland, and as such are dominated by black spruce, a common resident of wetland areas throughout the North American boreal forest. Another type of raised bog, the palsa, features a permafrost core, with the raised elevation the result of action by the ice. Black spruce is again the more noticeable dominant, but palsas have significant cover by Labrador tea, blueberries, and sedges.
Fens are often dominated by tamarack; with dwarf birch and bog willow; mosses such as Tomenthypynum, Depanocladus, and Campylium; sedges; and cottongrass.
In tidal flats and estuaries along the shores of Hudson and James Bays, a type of sedge-dominated marsh may develop. In addition to sedges, grasses such as tundragrass, alkaligrass, pendantgrass, and arrowgrass; and herbs such as primrose, bog star, and felwort are common.
Other vegetation types in the region include the dwarf birch-willow communities that flank marsh flats and river shorelines, and balsam-poplar communities found on alluvial and beach deposits.
Fauna and Change
Several large rivers flow through the Hudson Bay Lowlands into the Hudson or James Bays. Rivers that flow into Hudson Bay include the Churchill, Nelson, Hayes, Severn, and Winisk Rivers. Those that flow into James Bay include Attawapiskat, Albany, Moose, Harricana, and Nottaway Rivers. Whales such as beluga may be spotted in the larger river estuaries, such as that of the Churchill River near Churchill, Manitoba.
The Hudson Bay Lowlands biome is undergoing great change. One cause is geological: The Hudson Bay region is undergoing isostatic rebound, in which the landscape, formerly compressed under the great weight of the Laurentide Ice Sheet, is expanding vertically, in effect, getting higher. Vegetation belts shift northward to colonize land exposed by the retreating waters.
The other cause is climatic. Climate change is causing the landscape to warm. Some of the more striking effects are out over the Hudson and James Bays, where the icepack melts earlier and freezes later. But warmer temperatures disrupt the landscape as well, melting permafrost, increasing loss of water from the land surface via evaporation and transpiration, and increasing the risk of wildfire in the region. While wetlands may be the most heavily affected by the change, upland ecosystems are likely also to be adversely affected.
Bibliography
Abell, Robin, et al. “Freshwater Ecoregions of the World: A New Map of Biogeographic Units for Freshwater Biodiversity Conservation.” BioScience 58, no. 5 (2008).
Abram, Jenelle. "Peatlands of the Hudson Bay Lowlands." Story Maps, 6 Apr. 2021, storymaps.arcgis.com/stories/9bcd881f35f14f75a8c0ffc9cd2765ec. Accessed 6 Aug. 2022.
Barbour, Michael G. and William Dwight Billings. North American Terrestrial Vegetation, 2nd Ed. Cambridge, UK: Cambridge University Press, 1999.
Larsen, James A. The Boreal Ecosystem. New York: Academic Press, 1980.
Ritchie, J. C. “The Vegetation of Northern Manitoba: II. A Prisere on the Hudson Bay Lowlands.” Ecology 38, no. 3 (1957).
Sjörs, Hugo. “Bogs and Fens in the Hudson Bay Lowlands.” Arctic 12, no. 1 (1959).