Their efforts have produced the most comprehensive map to date of Great Lakes' stressors, and also the first map to explicitly account for all major types of stressors on the lakes in a quantitative way. David Allan, the project's lead researcher and a professor of aquatic sciences at U-M's School of Natural Resources and Environment said, "Despite clear societal dependence on the Great Lakes, their condition continues to be degraded by numerous environmental stressors. The map gives federal and regional officials an unprecedented scientific foundation upon which to sustainably manage the Great Lakes, the researchers conclude.
The environmental stress map was developed by a bi-national team of researchers from academia and environmental organizations known as the Great Lakes Environmental Assessment and Mapping (GLEAM) project. The team drew upon the latest and best data from Federal and state agencies as well as non-governmental organizations and individual researchers. The map represents the combined influence of nearly three dozen individual stressors and is incredibly detailed for a region spanning nearly 900 miles, showing impacts at the scale of half a mile. Thirty-four stressors were examined, including: coastal development, pollutants transported by rivers from agricultural and urban land, fishing pressure, climate change, invasive species and toxic chemicals (the full list is available from the Great Lakes Mapping website below).
To rank the relative importance of different stressors to ecosystem health, the team surveyed 161 researchers and natural resource managers from across the basin. Combining the mapping of multiple stressors with their ranking by experts to assess ecosystem health is an emerging new approach. Their work found high and low "stress" -- defined as human impacts like physical, chemical or biological disruptions that potentially have adverse effects on people, plants and animals -- in all five lakes. Ecosystem stress is highest closer to shores, but also extends offshore in some areas. Large sub-regions of moderate to high cumulative stress were found in lakes Erie and Ontario as well as in Saginaw and Green bays, and along Lake Michigan's shorelines. In contrast, extensive offshore areas of lakes Superior and Huron, where the coasts are less populated and developed, experience relatively low stress.
A key goal of the effort was to help lawmakers and natural resource managers better plan Great Lakes-area investments, such as those under the Great Lakes Restoration Initiative (GLRI), a Federal effort initiated in 2009 that is funding hundreds of projects at sites where ecosystem stress is very high. The initiative is the largest investment in the Great Lakes in two decades. Eleven Federal agencies developed an action plan to implement the initiative through 2014.
Some worrisome environmental stressors could not be included due to lack of adequate data across all five Great Lakes, and the team hopes to continue to map additional stressors as data become available. However, the cumulative stress index developed from 34 individual maps is unlikely to change much with new data, as simulations of cumulative stress using subsets of the full set of maps produced similar patterns. The researchers launched a new Great Lakes Mapping website to share their results with policymakers, planners and government officials in the region. The project will continue acquiring data to map stressors currently not included and will regularly update the stress maps. The GLEAM project began in 2009 with $500,000 from the Bloomfield Hills, Mich.-based Fred A. and Barbara M. Erb Family Foundation.