Ecological History of the Lake Superior Basin

The cumulative ecological changes from the fur trade, mining, logging, and farming on Lake Superior were profound. While contemporary observers understood that these rapid changes might cause problems, it was rare to recognize that Lake Superior’s geological context and history made the watershed particularly vulnerable to sudden ecological change. After the retreat of the ice, the Canadian Shield’s thin soils and high resistance of its rocks to weathering had ensured that Lake Superior was biologically unproductive and slow to accumulate sediments. Lake Superior’s geographic context meant that its waters were very cold, and that coldness shaped its ecology in profound ways. Lake Superior’s enormous size, which made planners hope that dilution might be the solution to pollution, actually worked against them. Lake Superior is large enough and cold enough that when thermal bars form, as mentioned above, they hold pollution where people and fish are more likely to encounter it.