Yukon-Mackenzie Ecozone

There's a land where the mountains are nameless,
And the rivers all run God knows where;
There are lives that are erring and aimless,
And deaths that just hang by a hair;
There are hardships that nobody reckons;
There are valleys unpeopled and still;
There's a land – oh, it beckons and beckons,
And I want to go back – and I will.
~Robert Service

The Yukon-Mackenzie Ecozone appears like a patchwork quilt from above, with numerous streams, rivers, and lakes littering the land. The relatively mild summers here result in a diverse community of vegetation and wildlife. The large rivers have lush riparian vegetation that provides suitable habitat for larger mammals, and the many wetlands are important destinations for migratory birds.

During the harsh winters, most visible life comes to a halt in this ecozone; solid ice covers the river channels and lakes, forcing fish to remain in the deep lakes and many species to migrate elsewhere in search of food. However, below the ice, some species of plants and animals continue their daily routines in these cold temperatures. On average, ice covers the lakes and rivers in the Yukon-Mackenzie area for 9 or 10 months of the year. During the remaining months, mild temperatures bring a rush of meltwater, creating large wetlands and filling the stream and river beds that dried up the previous summer. Freshwater habitats come alive with fish, migrating birds, and blooming vegetation.

The Yukon-Mackenzie area rests on the Canadian Shield and past glacial presence is evident throughout. Glacial scour is the process that formed most of the lakes in this region. As glaciers move, they scrape the bedrock, smoothing its surface and creating abrasion marks. Under the weight of large glaciers, depressions are created that later fill with meltwater to create lakes.

Two large rivers give the Yukon-Mackenzie Ecozone its name. The Yukon River, the 10th longest river in the world, is swift and clear, and drains over half of Yukon Territory. A unique feature of this river is the abundance of white volcanic ash in its sediments, a testament to a huge eruption that occurred over 1200 years ago. The Mackenzie River, the second longest in North America, drains Great Slave Lake directly and Great Bear Lake via one of its tributaries. These two lakes are the largest freshwater bodies located entirely within Canada.

The Yukon-Mackenzie region is classified as northern boreal forest or sub-arctic forest, and in contrast to other regions of the Arctic, trees are common. Aspen, birch, poplar, and stands of pine and spruce are able to thrive in the south. Willow, alder, and horsetails are common riparian vegetation. Much of the vegetation within the lakes, such as bladderworts and water-milfoil, is able to survive the ice cover by going dormant during the winter. Algae use a different adaptation; they lower the free water content in their cells to avoid freezing. Benthic vegetation, such as the mosses that line many lake bottoms, can survive the ice cover because the lake bottom sediments maintain water temperatures above freezing.

The Yukon-Mackenzie region provides important spawning grounds, feeding areas, wintering habitats, and migration corridors. Moose winter in the forests that border lakes and rivers in this area. The wolverine, grizzly bear, bald and golden eagles, and the trumpeter swan can be seen on the shores of the many lakes and rivers. The lush habitat is also prime for beavers, weasels, foxes, and coyotes. Fish, such as salmon, northern pike, lake trout, and whitefish, are common in the larger rivers and lakes.

Species diversity in this area is much higher than other regions of the Arctic because of the abundant water supply, milder temperatures, and flourishing vegetation. Despite the mild summers, wildlife must still adapt to cold, winter temperatures and frozen waters. Some fish and bird species migrate to warmer areas when winter approaches. Many invertebrates produce eggs that have protective coatings to resist freezing. Predatory copepods, such as calanoids and cyclopoids, are common invertebrates in arctic freshwater environments because zooplankton prey are abundant.