Walleye and yellow perch -- the backbone of the Great Lakes region's multibillion dollar recreation and tourism industry -- will likely be harder to catch as the lakes warm.
Algae will proliferate, sucking more oxygen from the water. Walleye and yellow perch are two cool-water species that likely will be out-competed for food by warm-water fish. Lake trout and brook trout are two others.
And the issue that scientists now view as the No. 1 threat to the ecological balance of the lakes -- invasive species -- will likely get worse as shipping seasons are extended and more exotic fish adaptable to warmer water enter the lakes.
The devastation, though, could be overshadowed by what happens to the shipping industry if lake levels become chronically lower, as predicted under the current regime of climate-change scenarios.
The two issues could work in tandem to wreak havoc on the region's economy.
Lake levels have risen and fallen in 30-year cycles since at least 1860, records show, but a study last fall issued by 75 area scientists from nearly 50 government, business, academic, and public-interest groups claimed warming and evaporation trends could cause Lake Erie water levels to drop 3.28 feet to 6.56 feet by 2066.
The estimates were based on findings by the Intergovernmental Panel on Climate Change, the world's most prestigious group of climatologists.
A subsequent paper that appeared in Environmental Science & Technology suggested Lake Erie and Lake Ontario water levels will become largely dependent on the rainfall they pick up from additional hurricanes and tropical storms. More violent weather is anticipated as the climate warms. Lakes Superior, Michigan, and Huron are too far north to pick up substantial amounts of rain from storms, the report stated.
Every inch lake levels fall affects the shipping industry and its economy by millions of dollars a year. That's especially true in Toledo, the most heavily dredged harbor in the Great Lakes.
"I don't think there has been much thought put into it by anybody," said Scott Thieme, chief of the U.S. Corps of Engineers' Great Lakes hydraulics and hydrology office.
He said he's aware of forecasts for water-level declines and perplexed why the government hasn't taken the issue more seriously, given what's at stake.
A big enough drop in water could even affect the future of the U.S.-Canada tunnel between Detroit and Windsor, he said.
Even now, the Corps of Engineers spends $20 million a year to dredge 4 million cubic yards of sediment from all Great Lakes harbors and channels, the equivalent of 400,000 truckloads of soil.
Nearly a quarter of all Great Lakes dredging occurs in the Toledo area. The 800,000 to 900,000 cubic yards of silt removed from the Toledo shipping channel in a typical summer is about three times as much as that taken from Cleveland-area waters.
The silt is mostly northwest Ohio farm soil that was blown or carried into the Maumee River by rain.
The solution isn't simply more dredging.
The Corps of Engineers is struggling to find places to put dredged silt from the Toledo shipping channel.
About two-thirds of it is redeposited in Lake Erie, a practice that Michigan and Ohio have been trying to get the federal government to phase out since the 1980s. The states say open-lake dumping hurts the region's fishing industry by muddying the water. But nobody has offered plans to build a confined disposal facility on land, either, because of the projected $200 million cost.
There is a bigger problem in the Detroit River, where only so much more dredging can occur before hitting bedrock. The river bottom was blasted in the 1920s and 1930s for a shipping channel. Blasting it deeper today would be a multibillion dollar project.
Toledo is one of several harbors with pipelines beneath their shipping channels. The lines carry chemical products, natural gas, as well as electrical, phone, and fiber optic cables. The cost of relocating those would be astronomical.
Even if relocating pipelines and blasting deeper through the Detroit River bedrock became viable, there "would be an awful lot of concern and resistance for environmental issues that there weren't years ago," Mr. Thieme said.
The Great Lakes region accounts for 70 percent of the nation's steelmaking capacity, 70 percent of its automobile production, and 55 percent of all heavy manufacturing. But it hasn't been moving cargo for such manufacturing as efficiently as it could.
Three of every four vessels leave their docks "light loaded" because of the lack of channel depth, according to testimony delivered to the House subcommittee on Energy and Water Development last year by James Weakley, president of the Lake Carriers' Association.
The 63 U.S.-flagged vessels represented by the association leave behind more than 8,000 tons of cargo per trip for every inch of lost channel depth.
Eight thousand tons of iron ore is enough to build 6,000 vehicles. Eight thousand tons of coal is enough to produce three hours of electricity for the Detroit metro area. And in the housing industry, 8,000 tons of limestone is enough to build 24 homes, according to Mr. Weakley's testimony.
"We might not lose the Port of Toledo, but it would need to accommodate wider ships or be bypassed," said Frank Quinn, a retired National Oceanic and Atmospheric Administration hydrologist who has studied lake levels since the 1960s.
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