The Great Lakes are feeling the heat from climate change.

As the world's largest freshwater system warms, it is poised to systematically alter life for local wildlife and the tribes that depend on it, according to regional experts. And the warming could also provide a glimpse of what is happening on a more global level, they say.

"The Great Lakes in a lot of ways have always been a canary in the coal mine," Cameron Davis, the senior adviser to the U.S. EPA on the Great Lakes, said last week. "Not just for the region or this country, but for the rest of the world."

And it seems the canary's song is growing ever more halting.

Lake Superior, which is the largest, deepest and coldest of the five lakes, is serving as the "canary for the canary," Davis said at a public meeting of the Interagency Climate Change Adaptation Task Force last week, pointing to recent data trends.

Total ice cover on the lake has shrunk by about 20 percent over the past 37 years, he said. Though the change has made for longer, warmer summers, it's a problem because ice is crucial for keeping water from evaporating and it regulates the natural cycles of the Great Lakes.

But the warming shows no sign of abatement. This year, the waters in Lake Superior are on track to reach -- and potentially exceed -- the lake's record-high temperatures of 68 degrees Fahrenheit, which occurred in 1998.

Analysis of several buoys that measure temperatures in the lake reveal that the waters are some 15 degrees warmer than they would normally be at this time of year, Jay Austin, a professor of physics at the University of Minnesota, Duluth's Large Lakes Observatory, said in a recent interview.

His analysis of National Oceanic and Atmospheric Administration data indicates that summer for the lake, which happens at about a 40-degree threshold, came about a month early this year.

A 'tremendously anomalous' year

"This year is just tremendously anomalous," he said. "This year ranks up there with the warmest water we have ever seen, and the warming trend appears to be going on in all of the Great Lakes."

While the warmer waters make for more comfortable swimming conditions for humans, they may also make for more habitable conditions for invasive species in places that have previously been relatively free of such pests.

Exhibit one, said James Kitchell, a professor of zoology at the University of Wisconsin, Madison's Center for Limnology, is the blood-sucking sea lamprey.

The jawless parasite attaches itself to the side of trout, bores a hole and sucks the trout's blood, growing to as long as 3 feet in the process, according to Kitchell. But in warmer weather, the lamprey may feed faster, grow bigger and lay more eggs, he said. The creatures will also become adults faster and require more frequent extermination, thanks to the warmer waters, warned Marc Gaden, a spokesman for the Great Lakes Fishery Commission, in an interview.

Meanwhile, the dead trout, with gaping holes in their sides, will sink to the seafloor below -- far from where humans can witness the evidence.

But the full impact of decades of water warming is not bound to the murky depths.

The warming may also threaten practices that are central to the "cultural identity" of indigenous tribes that live in the Great Lakes area and depend on certain weather and water conditions to farm wild rice, according to Nancy Schuldt, the water quality coordinator of the Fond du Lac Band of Chippewa Indians.

The Fond du Lac Band lives on a 101,000-acre reservation in northeast Minnesota about 20 miles inland from Lake Superior in the far western corner of the lake.

Low water levels may mean it's not safe to get canoes into the waters and hand-harvest rice in the traditional manner, she said, pointing to a rice operation by the Bad River Band of Lake Superior Chippewa that had to shut down in 2007 after drought made it too difficult to maneuver canoes. The rice itself is at risk of being phased out by other native species, she said, noting that the rice is "very sensitive to hydrologic changes."

Though tribes in this area are doing what they can to invest in clean energy and study local water temperature trends to help plan future adaptation strategies, "there's still really fundamental questions remaining" about what the future environment will look like, she said.

A 'cultural identity' at risk of being transformed

"Will there still be wild rice? Will there still be birch bark to harvest? Will there still be a sugar bush?" she asked. "Right now, we certainly don't have those answers."

While there is a certain amount of uncertainty in predicting climate change impacts, the various models forecast that the Great Lakes region may see lower lake levels "on the order of 1 to 2 feet, said EPA's Davis.

In February, the Obama administration rolled out a five-year Great Lakes Action plan dedicated to adapting to some of these effects and restoring the area.

The plan, which would cost more than $2 billion to carry out, lays out five central goals it hopes to address in the coming years: restoring lost wetlands, controlling invasive species, tackling runoff pollution, addressing toxics like mercury, and promoting accountability and education efforts.

As water levels decline, toxics need to get cleaned up, and "fast," said Davis. "The reason is that with climate change scenarios starting to kick in, we have to get those areas cleaned up so we aren't unwittingly circulating more contaminants than we need to," he said.

To adapt to the warmer temperatures, "The most important thing we can do is to use the best science in all the initiatives that are under way," added Andy Buchsbaum, the Great Lakes regional executive director of the National Wildlife Federation.

"Don't just look at the way things are now, but the way they are likely to be in the coming years, and use all the resources we have now in the service of preparing for climate change," he said.

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