Kayakers Circumnavigate Lake Superior

We have seen a lot of commercial fishing boats, but none with such a cool paint job. What effect do you think global warming will have on the fish populations in the Great Lakes?

Notes from the Trail - October 8, 2006
By Dave Freeman

As I write this, the usual sound of waves crashing on shore is accompanied by the drone of a coal powered paper mill near Ontanagon, Michigan. As we paddle through more populated areas we are encountering more and more industry, which contrasts sharply with our simple daily rituals or hauling water from the lake, gathering firewood, and using our own muscles to slowly propel ourselves around Lake Superior. Last week students told us that they were interested in learning about the effects global warming will have on the Great Lakes, which caused us to do some research and contemplate the issue as we paddle.

When the winds are strong, and our muscles are tired the thought of adding little motors to the back of our kayaks is tempting, but learning about climate change has emphasized the importance of traveling under our own power. Experiencing Lake Superior by kayak has humbled us in many ways, and it saddens me to think that the Great Lakes may be drastically altered by climate change. Hopefully some of the information we have gathered will make you think again about global warming and how it may affect us all.

The earth's climate has gone through many cycles of cooling and warming over time, as indicated by geologic and fossil records, but scientists are finding that humans are causing a more rapid change by adding "greenhouse gases" into the earth's atmosphere. These gases trap heat, like glass does in a greenhouse, and are making the earth warmer than it would normally be. Carbon dioxide, the most prevalent greenhouse gas, is produced by the combustion of fossil fuels and the clearing and burning of forests.

This unnatural warming could cause water temperatures of the Great Lakes to increase due to warmer summer air temperatures and more ice-free time. Warmer water temperatures could harm water quality by decreasing oxygen in the water and increasing the growth of algae. The warmer waters would also decrease habitat for cold water-loving fish like lake trout and whitefish. Several other kinds of trout and salmon would also experience habitat losses. We have seen a lot of commercial fishing during our travels, and I have to wonder how this would affect the commercial and sport fishing in Lake Superior.

A warmer climate would cause increased evapotranspiration (water lost to the atmosphere by evaporation and transpiration). This could mean a decrease in summer streamflows, causing reduced water quality. The flow of freshwater into the Great Lakes could decrease by 20 percent with a warming of 4 F. A decrease like this could result in a reduction of lake levels by a foot or more.

You may have heard that global warming will cause the polar ice caps to melt, resulting in the oceans rising. The opposite would be the case for the Great Lakes. It is predicted that Great Lake levels may decrease from 2-5 or more feet as climate change worsens. Lower lake levels would reduce inputs to hydroelectric power facilities, increase the concentration of water pollutants, and require more dredging to maintain ship channels.

Those are just a few of the changes that are possible in the Great Lakes region if global climate change continues at its present rate. With all those changes, just think about the effect on the plants and animals of the region.