Great Lakes Study Highlights Environmental Threats And Challenges
December 18, 2012

Great Lakes Study Highlights Environmental Threats And Conservation Challenges

April Flowers for - Your Universe Online

A research team, led by the University of Michigan, has developed a comprehensive map telling the story of human impact on the Great Lakes and identifying how "environmental stressors" stretching from Minnesota to Ontario are shaping the future of an ecosystem that contains 20 percent of the world's fresh water. The map, three years in the making, was a collaborative effort with the University of Wisconsin-Madison and a binational team of researchers from the Great Lakes Environmental Assessment and Mapping (GLEAM) project.

The results, published in a recent issue of the Proceedings of the National Academy of Sciences, describe an expansive and detailed effort to map and cross-compare environmental stresses and the ecological services provided by the five lakes.

"This study provides a benchmark for understanding restoration in the Great Lakes," says Peter McIntyre, assistant professor at UW-Madison. "Until now, restoration has usually been dominated by a piecemeal approach, but our team's synthesis of all major classes of environmental problems provides a more comprehensive perspective."

The efforts of this team have produced the most comprehensive map to date of the stressors in the Great Lakes region, which is home to more than 30 million people. It is also the first map to explicitly account for all major types of stressors on the lakes.

"Despite clear societal dependence on the Great Lakes, their condition continues to be degraded by numerous environmental stressors," said David Allan, professor of aquatic sciences at the University of Michigan's School of Natural Resources and Environment. The study concludes that the map will give federal and regional officials an unprecedented scientific foundation with which to sustainably manage the Great Lakes.

Showing the combined influence of nearly three dozen individual stressors, the map is incredibly detailed for a region spanning nearly 900 miles, showing impacts at the scale of half a mile. The team examined 34 stressors, including factors like coastal development, pollutants transported by rivers from agricultural and urban land, fishing pressure, climate change, invasive species and toxic chemicals.

The team surveyed 161 researchers and natural resource managers from across the basin, asking them to rank the relative importance of different stressors to the ecosystem's health. Assessing ecosystem health by combining the mapping of multiple stressors with their ranking by experts is an emerging new approach to large-scale conservation studies.

"Current efforts to conserve, manage and restore the Great Lakes often take a piecemeal approach, targeting threats one by one," Allan explained. "We need to recognize that the Great Lakes are affected by multiple environmental stressors, and devise strategies based on a full reckoning."

"The Great Lakes have been dying a death of a thousand cuts," says McIntyre. "The maps we've produced, the first of their kind, can help us devise better ways to stem the bleeding."

In all five lakes, the study found high and low "stress" factors, defined as human impacts like physical, chemical or biological disruptions that have potentially adverse affects on people, plants and animals. Ecosystem stresses are highest close to the shore but extend offshore in some areas as well. Lakes Erie and Ontario as well as in Saginaw Bay and Green Bay, and along Lake Michigan's shorelines were found to have large sub-regions of moderate to high cumulative stress. Lakes Superior and Huron, in contrast, were found to have extensive offshore areas where the coasts are less populated and developed with relatively low stress.

"What our team has done is to gather the best data on each of these stressors, and put it all together in a cumulative way," explains McIntyre, who began work on the study as a post-doctoral fellow at the University of Michigan and is now a professor at the UW-Madison Center for Limnology.

A host of human benefits, called ecosystem services, are provided by the Great Lakes. These range from recreational and commercial fishing to boating, beach use and birding, and their economic value is estimated in the tens of billions of dollars annually. The study compared maps of ecosystem services to maps of stress, finding that locations providing human benefits were often disproportionately stressed.

"Basically, our work itemizes the laundry list of things that need to be fixed and where they occur," said McIntyre. "This information can be used in any given location by local officials and citizen groups."

"We looked for a nexus between our threat maps and service maps, and were shocked to see that most of the high service sites are also on the high end of the threat spectrum."

Maps of this sort are called high-resolution spatial analyses. Tools like this are seen as an effective way to assess humans' impact on ecosystems. They measure environmental stressors and ecosystem services as they vary from place to place. Approaches such as these are emerging in coastal ocean management and are expected to guide similar efforts in the Great Lakes region, currently the focus of an ambitious restoration effort. These maps allow planners to identify locations where human benefits are greatest and ensure that all relevant stressors are accounted for when considering where to apply restoration funds.

"The Nature Conservancy and multiple partners are already working to attack many of these stressors in places like western Lake Erie, Green Bay and the coastal areas of Lake Ontario — the very places where nature and people are inexorably linked," said Patrick Doran, the director of conservation for Michigan and the Great Lakes at The Nature Conservancy.

"The cumulative impact map provides a quantitative perspective on how best to protect critical natural resources such as beaches, boating and fishing that support a vibrant tourism industry, as well as commercial fishing which remains important to local economies," Allan said. "Conducting this analysis at the scale of the entire Great Lakes basin fills an important gap in strategic prioritization to protect the Great Lakes and the services they provide to society."

A key goal of this study is to help lawmakers and natural resource managers better plan Great Lakes-area investments, such as those under the Great Lakes Restoration Initiative. The Great Lakes Restoration Initiative is a federal effort initiated in 2009 that is funding hundreds of projects at sites where ecosystem stress is very high as a collaborative effort between eleven federal agencies to be implemented through 2014. Giving away a total of $1 billion, this is the largest investment in the Great Lakes in two decades.

Due to lack of adequate data across all five Great Lakes, some worrisome environmental stressors could not be included, although the team hopes to continue to map stressors as additional data becomes available. The cumulative stress index, however, was developed from 34 individual maps and is unlikely to change much with the new data. Simulations of cumulative stress using subsets of the full set of maps produced similar patterns.

To share their results with policymakers, planners and government officials in the region, the research team launched a new website where the full list of stressors is available. They intend to continue gathering data to map stressors, which have not been included and will regularly update the stress maps.