Dear EarthTalk: What are the major threats to the Great Lakes in the United States and what’s being done to address them?
—Saul G., Racine, WI
The Great Lakes watershed is a unique and important ecosystem that contains some 95 percent of America’s fresh water surface area, and is a continental hub for birds, fish and other wildlife. According to the National Audubon Society, the Great Lakes provide habitat for some 400 bird species. But it is the region’s exploding human population—now at 42 million—that is causing many environmental problems.
Major threats include toxic and nutrient pollution, the growing presence of non-native invasive species, and the destruction of critical wildlife habitat. In addition, the region’s residents worry that other parts of the country and world facing water shortages will find ways to divert Great Lakes water to quench their far-off thirsts. Also, it remains to be seen what kind of impact global warming will have on the region.
Perhaps the issue that gets the most attention in the region is the menace of invasive species. They arrive via heel, tire, railway and ship, and are profoundly altering the region’s ecology. The most notorious case is that of the zebra mussel which, originally native to southeast Russia first arrived in the late 1980s on ocean-going ships via the St. Lawrence Seaway. Aside from outcompeting native species for food, they have absorbed toxic PCBs dumped years earlier and transferred them up the food chain in being eaten by round gobies (also a non-native species), which in turn are preyed upon by walleyes, a popular sport fish.