Great Lakes still clean, but threatened by sprawl
Date: 12-Sep-01
Country: CANADA
The fourth joint U.S.-Canadian survey of the Great Lakes noted progress in cleaning up pollutants and bringing birds and fish back to the waters. But non-native species were spreading at an alarming rate in some parts of the massive network of waterways, and many fish are still too poisonous to eat.
"Advisories related to humans eating fish are still in place on all the Great Lakes, even though chemical contamination is decreasing in most species," the report said.
"Contaminant levels will need to continue to decline for many years before advisories can be lifted, or in some areas and cases even modified."
The Great Lakes Basin contains some 20 percent of the world's fresh water and 16,000 km (10,000 miles) of shoreline.
Bordered by beaches, factories, residential districts and nature preserves, the area around the lakes is home to more than 33 million people, including residents of the big cities of Chicago, Toronto and Detroit.
The 82-page report was compiled by Environment Canada and the U.S. Environment Protection Agency, looking at 33 key indicators to assess the risks facing the lakes, the waterways that connect them and the shorelines.
Three indicators ranked as good, including the quality of the drinking water; five were improving, including the chemical levels in edible fish; seven were deteriorating; and one was poor - the way in which "exotic species" were spreading in the waters of the five lakes.
"Introductions of non-native species will continue because of increasing global trade, new diversions of water into the Great Lakes," the report said. "It is essential that entry mechanisms be closely monitored and effective safeguards introduced and adjusted as necessary.
Many new, non-native species arrive in the Great Lakes in the ballast water of international cargo ships.
The scientists said they needed specific targets before they could evaluate targets like urban density, water use or the levels of plankton close to the shore and in open waters.
"Continuing pressures from human population growth pose real threats to the future sustainability of the Great Lakes Basin," said Harvey Shear, Canadian co-chairman of the group that drew up the report.
"All the citizens of the basin have a job to ensure that we don't lose that most precious of jewels."
