American researchers have developed a comprehensive map that shows how the Great Lakes, which account for over 20 percent of the world's fresh water resource, in North America have been affected by humans.
Researchers from the University of Michigan and colleagues took three years to produce the most comprehensive map of the Great Lakes, highlighting stressors and the ecological importance of the five lakes located on the Canada-US border.
"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 Michigan's School of Natural Resources and Environment, who led the study.
The map gives authorities an unprecedented scientific foundation upon which to sustainably manage the Great Lakes, the researchers said, the journal Proceedings of the National Academy of Sciences reports.
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, according to a Michigan statement.
Thirty-four stressors were examined, including coastal development, pollutants transported by rivers from agricultural and urban lands, fishing pressure, climate change, invasive species and toxic chemicals.
The environmental stress map was developed by a bi-national team of researchers from academia and environmental organisations 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 organisations and individual researchers.
It 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.
"Current efforts to conserve, manage and restore the Great Lakes often take a piecemeal approach, targeting threats one by one," Allan said.
"We need to recognize that the Great Lakes are affected by multiple environmental stressors, and devise strategies based on a full reckoning."