A first-of-its-kind map that pulls together numerical data on nearly three dozen factors that affect the Great Lakes ecosystem shows that the lakes with the most urban and agricultural development in their watersheds are also those with the greatest environmental stress.
Lakes Erie and Ontario, the easternmost lakes, are challenged by high coastal population densities, an industrial legacy and phosphorous pollution from agricultural runoff. They are also downstream from wind currents that drop nitrogen generated by industries and power plants into their waters.
But the map’s patches of high-stress red and yellow should not be misinterpreted. The color scale is a relative measure that compares the combined stress of the 34 environmental indicators in a particular area to the stress level of the lake system as a whole.
To create the maps, the research team queried some 160 experts from universities, nonprofits and government agencies in the United States and Canada and compiled a list of 50 key biological, chemical or physical indicators, of which two-thirds had data sufficient enough to be plotted.