The Great Lakes are under the threat of global warming and Congress needs to enact a comprehensive plan to restore the health of the lakes.

Warming over the next century could lower lakes and expose toxic sediment that has been buried and cause heavy rains that could lead to more sewer overflows, threatening water quality, a new report by the Healing Our Waters-Great Lakes Coalition says. Climate change could reduce scant ice cover observed in recent winters, it could increase evaporation rates that could lead to dropping water levels in the five lakes.

The Healing Our Waters-Great Lakes says global warming could lower lake levels up to 3 feet over the next century. Other threats mentioned in the report include the damage to fish habitats, worsening pollution from antiquated sewage treatment plants, a greater influx of invasive species of fish, plants and mussels. Daily high temperatures in the region will increase 5.4 to 10.8 degrees relative to what was typical from 1961-1990, with wintertime temperatures increasing even more than summer temperatures, the report noted.

The report was based on existing scientific research, said Richard Scavia, a professor of natural resources at the University of Michigan.

“Climate change is threatening the health of the Great Lakes and jeopardizing efforts to restore them,” the coalition's Jeff Skelding said in a teleconference.

“Climate change is already affecting the Great Lakes, and no matter what we do now, the those impacts will increase in the future,” said Donald Scavia, Ph.D., report co-author and professor of Natural Resources and Environment at the University of Michigan. “But we can counter those impacts by restoring the Great Lakes to make them more resilient. At the same time, we need strong national efforts to cut greenhouse gas pollution so that the impacts don’t become so severe that they overwhelm the Great Lakes.”

The Great Lake Compact will go to US Congress for the final approval after all states pass it. It still must be approved by the Ohio legislature.

The report also recommends several policy solutions, such as protecting the Great Lakes from water diversions by passing the Great Lakes Water Resources Compact, a regional agreement to ban diversions outside the region and promoting conservation within the region, reducing greenhouse gas emissions to limit the magnitude of change to our climate and ecosystems and restoring the Great Lakes through full funding and implementation of the Great Lakes Regional Collaboration Strategy, a comprehensive plan put forward by more than 1,500 citizens and backed by the region’s mayors, governors and Congressional delegation.