Climate Change at Isle Royale: Loons

Isle Royale National Park contains more than one hundred loon territories, supporting the only known population that still breeds in Great Lakes waters. Loons have a low reproduction rate, and the species is considered threatened in Michigan. The effects of climate change further impact the viability of this Northwoods icon.

Loons will abandon their nests if stressed by human or environmental factors.

Paul Brown

Climate Concerns

Water Levels

Breeding loon pairs construct their nests out of marsh grasses and other plant materials along coasts of larger lakes. This fragile construction can be easily washed out by waves, storms, or wakes made by boats. Nest destruction leaves a breeding pair unable to lay eggs or raise chicks. As temperatures increase and severe storm surges take place, the water levels of Lake Superior and Isle Royale’s interior lakes continue to rise. Increased waves and high water levels can destroy nests and decrease availability of nesting habitat, adversely affecting loon population.

Water Temperatures

Increasing water temperatures promote the growth of algae and aquatic plants. On Isle Royale, this new growth could affect water visibility and water oxygen levels. These water conditions affect fish populations, which loons and their chicks depend on.

Bottom Line

As the climate warms, the nesting success of loons is threatened due to changing water levels, and increasing temperatures affect water visibility and ecosystem structure of the lakes they inhabit.

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