III.

Climate and Ecology

The climate is arctic in the northern shield, where the average January temperature is about -32° C (-25° F). The growing season lasts less than 40 days a year, and lakes are free of ice for only about three months each year. North-west of Hudson Bay are vast regions of permanently frozen subsoil. The more temperate southern shield has forests of pine and northern hardwoods. Tundra, carpeted with sedges, grasses, lichens, and dwarf shrubs, lies north of the forests. Muskegs (sphagnum bogs), swamps, and lakes are found throughout the shield area. Black bears, brown fox, and beavers occupy the subarctic zone, while polar bears and arctic fox live in the arctic zone. Caribou migrate to the arctic in the summer to feed on the lush tundra plants and migrate southwards in the winter to the boreal forest.