The Midwestern Canadian Shield forests ecoregion covers much of northern Saskatchewan, north-central Manitoba (north and east of Lake Winnipeg) and a portion of northwestern Ontario.
This ecoregion is classified as having a subhumid high- to mid- boreal ecoclimate. It is marked by cool summers (except the Lac Seul Upland area which has warm summers) and very cold winters. The mean annual temperature ranges from -4°C to 0.5°Celsius (C); the mean summer temperature ranges from 11.5°C to 14°C; and the mean winter temperature ranges from -20.5°C to -14.5°C. In each case, the Lac Seul Upland area represents the warmest temperature in the ecoregion , and the Athabasca Plain, Churchill River Upland and Hayes River Upland regions represent the cooler temperatures. Mean annual precipitation ranges from 350-700 millimetres (mm), with the wettest areas being in the southeastern portions of the Lac Seul Upland and Hayes River Upland.
The Midwestern Canadian Shield Forests span from northern Alberta east to western Ontario. The Athabasca Plain, Churchill River Upland, Hayes River Upland and Lac Seul Upland (TEC 87-90) are the regions within this ecoregion (Ecological Stratification Working Group 1995). Rowe’s (1972) Boreal forest sections include: Central Plateau, Upper and Lower English River, Upper Churchill, Nelson River, Northern Coniferous, Athabasca South and Northwestern Transition (8, 11, 14, 20, 21, 22a and b and 27).
Permafrost occurs sporadically throughout this ecoregion, except in the area of the Lac Seul Upland, which has a warmer climate. Wetlands are extensive in the regions of the Lac Seul Upland and the Athabasca Plain, and numerous small to large lakes are a prominent feature of the entire ecoregion. Archean rocks form steeply sloping uplands and lowlands in the Churchill River Upland and Hayes River Upland, while the Archean bedrock of the Lac Seul Upland area forms more broadly sloping uplands and lowlands. The ecoregion is covered with undulating to ridged glaciolacustrine or fluvioglacial deposits with occasional hummocky bedrock ridges and knolls.
A portion of this ecoregion (the Athabasca Plain and the Churchill River Upland) forms part of the continuous coniferous boreal forest that extends from northwestern Ontario to Great Slave Lake in the Northwest Territories. Forests of this ecoregion are dominated by stands of black spruce (Picea mariana) and jack pine (Pinus banksiana), with a shrub layer of ericaceous shrubs (Ericaceae) and a ground cover of moss and lichens. Depending on drainage, surficial material, and local climate, trembling aspen (Populus tremuloides), white birch (Betula spp.), white spruce (Picea glauca), balsam poplar (Populus balsamifera), and balsam fir (Abies balsamea) also occupy significant areas of this ecoregion. Poorly drained areas covered by fens and bogs are dominated by black spruce. Bedrock exposures have few trees and are covered with lichens. Fire is an important disturbance regime in this ecoregion, particularly on conifer-dominated dry sites, such as the Athabasca Plain.
Characteristic wildlife include moose (Alces alces), black bear (Ursus americanus), woodland caribou (Rangifer tarandus ssp. caribou) (for whom there is important winter range in Athabasca Plain), barren-ground caribou (Rangifer tarandus ssp. arcticus), lynx (Lynx canadensis), wolf (Canis lupus), beaver (Castor canadensis), otter (Lontra canadensis), marten (Martes americana), ermine (Mustela erminea), fisher (Martes pennanti), muskrat (Ondatra zibethica), snowshoe hare (Lepus americanus), red-backed vole (Clethrionomys gapperi), red squirrel (Tamiasciurus hudsonicus), least chipmunk (Tamius minimus), ducks, geese, pelican (Pelecanus erythrorhynchos), sandhill crane (Grus canadensis), spruce grouse (Dendragapus canadensis), sharp-tailed grouse (Tympahuchus phasianellus), willow ptarmigan (Lagopus lagopus), common nighthawk (Chordeiles minor), red-tailed hawk (Buteo jamaiccensis), raven (Corvus corax), common loon (Gavia immer), bald eagle (Haliaeetus leucocephalus), gray jay (Perisoreus canadensis), hawk owl (Surnia ulula), great-horned owl (Bubo viriginanus), herring gull (Larus argentatus), double-crested cormorant (Phalacrocorax auritus) and several other passerine species.
Habitat loss and degradation
Up to 80 percent of this ecoregion remains as intact habitat, although that number drops to an estimated 65 percent in Manitoba. The principal causes of habitat loss are forestry (rapidly expanding), mining (uranium, nickel, gold, copper) and flooding from hydro-electric development.
Remaining blocks of intact habitat
Most of the ecoregion remains relatively intact.
Degree of fragmentation
The following units have some level of environmental protection:
- Opasquia Provincial Wilderness Park - northwestern Ontario: 4730 kilometres squared (km2)
- Woodland Caribou Provincial Wilderness Park - northwestern Ontario: 4500 km2
- Atakaki Provincial Wilderness Park - eastern Manitoba: 3930 km2
- Lac La Ronge Provincial Park - central Saskatchewan: 3011.35 km2
- Amisk Provincial Park - north-central Ontario: 2,77 km2
- Athabaska Sand Dunes Provincial Wilderness Park: northwestern Saskatchewan
- Pipestone River Provincial Waterway Park - northwestern Ontario: 973.75 km2
- Trout Lake Provincial Park - northwestern Ontario: 78.5 km2
- Pakwash Provincial Park - northwestern Ontario: 39.93 km2
- Jan Lake Ecological Reserve - east-central Saskatchewan: 20.7 km2
Types and severity of threats
Major or potential increases in the annual allowable cut in large scale forestry licenses, new hydroelectric dams and major transmission corridors, and extensive mineral exploration are increasing the level of threat to this ecoregion as a whole.
Suite of priority activities to enhance biodiversity conservation
Establish protected areas in the following locations:
- Area around Cree Lake in Saskatchewan
- Foster Lake area in Saskatchewan
- Churchill River corridor in Saskatchewan
- Reindeer Lake in Saskatchewan
- Protection standard upgrades to Tom Lamb Wildlife Management Areas in Manitoba
- Implement recommended actions in Manitoba with respect to this ecoregion according to the schedule established in the 1996-1998 Action Plan.
- Earth’s Environment
- Endangered Spaces Campaign, Manitoba
- Endangered Spaces Campaign, Saskatchewan
- Environment North
- Federation of Ontario Naturalists
- Manitoba Future Forest Alliance
- Manitoba Naturalists Society
- The Nature Conservancy, Manitoba
- Nature Saskatchewan
- Resource Conservation Manitoba
- Saskatchewan Environmental Society
- TREE - Time to Respect the Earth
- The Wildlands League
- World Wildlife Fund Canada
- J. Shay, A. G. Appleby, G. Whelan Enns, T. Gray, K. Kavanagh, M. Sims, G. Mann, World Wildlife Fund. 2001. Midwestern Canadian Shield forests
Disclaimer: This article contains information that was originally published by the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth have edited its content and added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.