The allure of the Great Lakes' islands needs to be tempered by careful conservation, scientists warn after cataloging their biological value.
Across the Great Lakes, there's growing interest in the ecological importance of islands -- and the need to keep them free of invasive plants, pests and other threats.
Now, a first-ever atlas compiled by U.S. and Canadian researchers has catalogued their biological value -- and identified looming threats from expanding homes, resorts, roads and marinas. The lakes contain more than 32,000 islands, making them the world's largest collection of fresh water islands, according to the report.
"Islands have a lot of shoreline, they have a lot of rare species and habitats, and in many cases they're in better condition than the mainland," said Dan Kraus, co-author of the atlas and conservation science manager for The Nature Conservancy of Canada.
The isles are extremely diverse, ranging from tiny rocky shoals, to groupings that form sandy archipelagos, to larger islands, such as Isle Royale in Lake Superior, with their own thin soils and microclimates.
The recently published atlas, "Islands of Life," identifies each island in the system, scores them on the basis of their biological diversity, and details what's known about potential threats. The intent, its authors say, is to pool international data to prioritize key islands for increased protection or conservation.
From forests to grasslands
Because of their isolation, many islands have distinct mixes of plants and animals, some of which do not occur on the mainland. Apples do not need to be sprayed on Beaver Island in Lake Michigan, for example, because there are no pests to infest them. Arctic plants grow on Isle Royale, left behind when the glaciers retreated thousands of years ago and able to survive in the island's lake-cooled temperatures. Woodland caribou roam and swim between the Slate Islands, an archipelago at the northern tip of Lake Superiorin Ontario.
The islands also provide critical habitat for spawning fish, nurseries in their offshore shoals, and nesting areas for tens of thousands of gulls, terns, pelicans, cormorants and herons. The isles' perimeters may be fringed with moss-shrouded forests because of the ocean-like climate near the lake, and then change abruptly to other vegetation a mile or two inland with higher temperatures. Some islands contain dune grasslands that are found nowhere else in the world.
University of Minnesota wildlife Prof. Francie Cuthbert has studied colonies of waterbirds for the past three decades, including aerial surveys of hundreds of islands and field work on about 150.
"When we get to a remote island, I tell some of my field researchers that we may be the only people who set foot here all summer long," she said.
Some birds are island-dependent and very vulnerable, she said, because their main defense as ground-nesting species is their isolation from raccoons, coyotes and other predators. Some of the Apostle Islands in Wisconsin are important nesting sites, she said.
Islands in all of the Great Lakes are key for migrating songbirds, she said, which can fly across a lake if weather conditions are good, but often need safe places to stop, rest and feed on their journey south.
Cuthbert said there's something special about islands that appeals to many people, not just instrument-toting scientists. "They offer isolation, defined boundaries, complete freedom, especially if they're uninhabited, and a great sense of adventure," she said.
Because of their isolation and ruggedness, and often-difficult weather conditions to reach them, many Great Lakes islands have been too remote to receive much attention.
That is changing, said David Ewert, director of conservation science for The Nature Conservancy's Great Lakes program. Personal watercraft make it easier for explorers to reach islands. Some areas, especially in Lake Erie, have allowed extensive residential development, and new resorts, marinas and roads that cater to tourists. Other concerns include wind power development, oil and gas exploration, gravel quarries, climate change and invasive plants and animals.
Ewert, co-author of the conservation atlas, hopes that it will provide a foundation for greater understanding of island vulnerability so that potential problems can be avoided.
"Islands could have the option of not being invaded by certain plants, animals and pathogens like the West Nile virus," he said, if land managers and island residents take preventative action. And islanders should learn from previous mistakes, such as introducing white-tailed deer or turkeys for hunting, that can drastically change an island's entire ecosystem.
The atlas identifies 2,591 islands in Lake Superior, many on the Canadian side, with more than 1,500 miles of island coastline. Most of the islands are owned by federal, state or provincial governments, and about three-fourths of the total land is protected.
The good news, said Kraus, is that many islands in Superior and elsewhere are in fairly good shape, and because of their isolation have escaped over-development, intensive farming and other mainland problems.
"In some ways it's kind of our second chance to protect Great Lakes coastal areas if we can do a good job protecting these islands," he said.
Tom Meersman • 612-673-7388