Development along the shores of Lake Superior could be the greatest threat to the lake, scientists said during a conference in Duluth.
The panel of scientists who spoke Monday agreed that pollution, rising temperatures and invasive species also threaten the world's largest freshwater lake and its cold, sensitive ecosystem.
But several scientists said the lake is still in generally good health.
For example, most toxic pollutants in the lake have decreased in recent years, said Deb Swackhamer, director of the University of Minnesota's Institute on the Environment.
The potential for more runoff, erosion and destruction of habitat will increase as more people develop and occupy the lake's shores, said fisheries biologist Mark Ebener.
"The fish communities of the middle of Lake Superior are very healthy," said Ebener, who works for the Chippewa-Ottawa Resource Authority in Sault Ste. Marie, Mich. "The part of the ecosystem that faces the most problems are the tributaries and nearshore areas."
Ebener said invasive species -- such as sea lamprey and zebra mussels -- continue to be a problem, but he warned that human pressures are greater.
"We are still the worst enemy of the aquatic community," he said.
The conference, called "Making a Great Lake Superior," continues through Wednesday at the Duluth Entertainment Convention Center. More than 450 people have participated.