Great Lakes show improvement, but concerns remain
By Dan Schneider
Published June 16, 2007
TORONTO — The health of the Great Lakes ecosystem is improving in some ways, but population growth, climate change and invasive species continue to raise troubling concerns about the future of the waters, according to a new report by Environment Canada and the U.S. Environmental Protection Agency.
The report diagnoses the Great Lakes’ well-being as ‘‘mixed,’’ said Environment Canada’s Nancy Stadler-Salt.
While the Great Lakes continue to be a good source for treated drinking water, and levels of toxic chemicals have been significantly reduced over the last 30 years, there are some problems that can’t be fixed, she said.
The report lists invasive or non-native species among the major threats to the biodiversity and natural resources of the Great Lakes region, second only to habitat destruction.
In Lake Superior, the sea lamprey is the non-native species causing the biggest problems, according to U.S. Fish and Wildlife Service Fish Biologist Bob Kahl, who works with that agency’s Sea Lamprey Management program. Sea lampreys made their way from the Atlantic Ocean into the Great Lakes through man-made shipping canals, making their first appearance in Lake Superior in the late 1930s.
The populations of the parasitic sea lamprey exploded in the Great Lakes in the 1940s and ’50s, causing disastrous impact particularly to lake trout populations. But Kahl said lately, control methods such as traps, barriers and lampricides have stemmed the growth of the lamprey population.
“I would say it’s one where we are holding our own pretty much on controlling in Lake Superior and the other Great Lakes,” Kahl said. “We’re looking at some additional means of control.”
In the western portion of Lake Superior, another aquatic invasive is emerging.
“In the stream estuary situations, in the bays, particularly in western Lake Superior, the ruffe is starting to be a problem,” Kahl said. “It’s a fish from over in Europe that came in with ballast water and was first found in the Duluth Superior Harbor and I believe that was in the mid-1980s.”
He said the ruffe compete for the same food sources as native fish like perch.
The report says more than 300 invasive or non-native species now thrive in the Great Lakes basin — and their destructive, parasitic behaviors are difficult to contain.
‘‘That’s a huge concern, (especially) how they compete with our native species and in some cases, may replace them or drive them out of certain habitats,’’ Stadler-Salt said.
‘‘And once they’re here, they’re probably next to impossible to eradicate — it’s just learning how to control them.’’
In the report, the aquatic non-native species situation in Lake Superior was rated fair and unchanging. In the other four Great Lakes, however, the situation was rated poor and deteriorating.
Some invasive species traveled to the Great Lakes basin in the ballast water of cargo ships.
While research is ongoing to find a way to treat ballast water to stop the spread of invasive species, there’s still no solution, she said.
The report also suggests it is virtually a given that climate change will have an impact on the Great Lakes region.
‘‘All the impacts aren’t known, but we know that storms are going to get more severe,’’ Stadler-Salt said. ‘‘We may have shorter winters and less ice coverage on the lakes in the winter.’’
Kevin Crupi, a meteorologist with the National Weather Service in Marquette, said if predictions of warmer temperatures from climate change prove true, Lake Superior water levels may continue to fall.
“If the whole premise of our global warming and the temperature increase comes true, there’s going to be more evaporation,” Crupi said.
According to hydrologists, evaporation was one of the major causes of Lake Superior’s current near-record low water levels.
Still, Crupi said the big lake’s water levels are cyclical. He pointed out that while the lake was down during drought years in the late 1990s, it recovered in 2003 and 2004 to about normal levels.
“There’s natural cycles with this lake level,” Crupi said.
Crupi said precipitation will be the big variable with climate change.
He said current thinking in the meteorological community holds that climate change will lead to fewer and more localized storms, but that these storms would generate more rain.
Drought conditions in northeastern Minnesota and adjoining Ontario, Canada are another major factor in the current low water levels in Superior.
An altered climate and lower water levels would also affect wetlands and continue to force wildlife from their natural habitats.
The report gave Lake Superior a “good” rating for wetland plant health in its coastal wetlands.