A Changing Wilderness Refuge

An algal bloom occurring in Chickenbone Lake.

Lynette Potvin

Lake Superior insulates Isle Royale’s wilderness from many outside forces. However, annual monitoring completed by the Great Lakes Inventory and Monitoring Network (GLKN) reveals that despite its isolation, human-caused global changes have affected island ecology.

One of these effects comes in the form of harmful algal blooms (HABs), which are formed when potentially toxic cyanobacteria reproduce rapidly under the right conditions. The first known HAB reported on Isle Royale was on Lake Richie in 2007. A sediment core revealed it was the first HAB to occur there in 150 years. Why is this happening? Warmer temperatures cause ice to melt off Isle Royale’s inland lakes earlier in the year, giving wind a chance to mix up the water. Algae and nutrients move up from the bottom, and sun exposure creates ideal growing conditions. Today, HABs occur on almost all of Isle Royale’s inland lakes.

On land, annual surveys show a decline among insect-eating birds, especially the three most common species: the Nashville warbler, winter wren, and ovenbird. Because many island birds are migratory, habitat changes on their wintering grounds and loss of migratory stopover sites are major factors in their decline. Global temperature and precipitation changes are also in play, changing island forests and shifting the times insects are available for birds to eat. These changes may influence a high turnover of songbird species populations on Isle Royale in the future.

GLKN's programs show that humans are interconnected with wildness, even from afar. Today, Isle Royale’s wilderness remains a refuge to both humans and wildlife. But for how long?

Ted Gostomski
Science Writer/Biologist, Great Lakes Inventory and Monitoring Network