It takes more than a village to save isles
MINNEAPOLIS - 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.
A new atlas compiled by U.S. and Canadian researchers catalogues their biological value and identifies threats from expanding homes, resorts, roads and marinas. The lakes contain more than 32,000 islands, making them the world's largest collection of islands in fresh water, according to the atlas.
"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 with their own thin soils and microclimates, such as Isle Royale in Lake Superior.
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.
Because of their isolation, many islands have distinct mixes of plants and wildlife, some of which do not occur on the mainland. For example, apples do not need to be sprayed on Beaver Island in Lake Michigan, 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 Superior in Ontario.
The islands also provide 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 oceanlike 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.
Francie Cuthbert, a University of Minnesota professor, has studied colonies of water birds 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," Cuthbert 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 places to stop, rest and feed on their journey south.
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.