The Great Lakes—Michigan, Superior, Huron, Erie, and Ontario—form the largest-surface freshwater system in the world, together holding nearly one-fifth of the Earth's surface freshwater. The Great Lakes have over 10,000 miles (16,000 kilometers) of shoreline and serve as a drain for more than 200,000 square miles of land, ranging from forested areas to agricultural lands, cities, and suburbs.
The Great Lakes watershed includes some of North America's more fascinating wildlife, such as the gray wolf, Canada lynx, moose, and bald eagle. The lakes themselves are home to numerous fish, including lake whitefish, walleye, muskellunge, and trout. Millions of migratory birds pass through the region during their spring and fall migrations.
The Great Lakes region has been home to Native Americans for nearly 10,000 years. The first Europeans arrived in the 1600s and began to utilize the region for animal furs. It wasn't long before more settlers were drawn to the region seeking farmland.
Today more than 35 million people live in the Great Lakes basin in Canada and the United States. The Great Lakes are important sources of drinking water, irrigation, transportation, and recreation opportunities such as fishing, hunting, boating, and wildlife watching. The Great Lakes are a critical component of the regional economy on both sides of the border.
The land surrounding the Great Lakes was once dominated by forests and grasslands interspersed with wetlands. Many of the wildlife that still call the region home exist in the remnants of those habitats, such as the gray wolf, moose, and beaver. Other mammals in the Great Lakes include the Canada lynx, little brown bat, river otter, and coyote. A variety of bird species also live in these habitat remnants. The Great Lakes region is important for many species of migratory and resident birds, particularly waterfowl, neotropical migrants, and birds that nest in colonies. The Great Lakes region provides important breeding, feeding, and resting areas for birds like the bald eagle, northern harrier, common loon, double-crested cormorant, common tern, bobolink, least bittern, common merganser, and the endangered Kirtland's warbler.
The Great Lakes are actually quite different from each other, and because of this variation, different numbers and varieties of fish and other aquatic wildlife can be found in each lake. Lake Superior, the largest of the lakes, is cold and deep. Lake Erie is one of the smallest of the Great Lakes and is relatively shallow and warm. Walleye, yellow perch, lake sturgeon, brook trout, lake whitefish, muskellunge, and introduced salmon species are among the many kinds of fish in the Great Lakes. Some fish are undergoing restoration efforts, such as lake sturgeon and lake trout.
Despite their great size, the Great Lakes are actually very vulnerable to pollution. The amount of water entering and leaving the lakes each year is less than one percent of the total in the lakes. Persistent chemicals that enter the lakes can remain for many years, with many building up in the food web. The source of toxic pollutants includes decades of industrial waste, raw sewage overflows, runoff from cities, and mining operations. Excess nutrients that throw the ecosystem out of balance enter the lakes from agricultural runoff and untreated sewage.
The impacts of climate change are already being observed in the Great Lakes. Increasing air and water temperatures mean increased evaporation from the lakes, declining lake levels, and worsened water quality. The Great Lakes are already highly stressed, and climate change will worsen existing threats to the Great Lakes, including making the lakes more suitable for invasive species, drying coastal wetlands that filter pollution, exposing toxic sediment pollution, and increasing the number of intense storms leading to sewage overflows.
Invasive species have significantly changed the Great Lakes by competing with native species for food and habitat. They foul beaches, harm fisheries, clog water infrastructure, and lead to the regional extinction of species. More than 180 non-native species have entered the Great Lakes, and a new species is discovered every 28 weeks on average.
Most invasive species were transported in the ballast water of ocean-going ships. However, Asian carp are threatening to take hold in the Great Lakes by swimming up artificial channels that connect Lake Michigan to the Mississippi River system.
A proposal to mine sulfide metals in public forests only miles from Lake Superior threatens wildlife and water in the Great Lakes basin. Sulfide mining has a terrible record of destroying streams and endangering public health. This dangerous form of mining threatens to destroy pristine fish habitat, poison drinking water sources, and pollute the Great Lakes.
In Focus: Climate Change
The Great Lakes are a crown jewel of North America, holding nearly one-fifth of the planet's surface freshwater. They have nearly 11,000 miles of shoreline and harbor, more than 530,000 acres of coastal wetlands and the world's largest freshwater delta (in Lake St. Clair). They range from the cold and deep waters of Lake Superior to the relatively warm and shallow waters of Lake Erie.
The watershed drains more than 200,000 square miles ranging from heavily forested areas to mixed urban and agricultural development, and supports approximately 6,000 species. The lakes are home to numerous fish, including species undergoing restoration efforts such as lake trout and lake sturgeon, and species that are popular in commercial or recreational fisheries, including lake whitefish, walleye, muskellunge and several introduced salmon species.
The Great Lakes are important sources of drinking water, economic livelihood and recreation opportunities for millions of Americans and Canadians. Recreational boating in the eight Great Lakes states produces more than $35 billion in economic activity annually, and fishing, hunting and wildlife watching amount to more than $18 billion in annual economic activity in these states.
Threats from Climate Change
Climate change adds yet another stress to a Great Lakes system already struggling with aquatic invasive species, deleterious land use changes, nonpoint source pollution, toxic chemical contamination, and coastal habitat degradation/wetlands loss. Potential climate change impacts include reduced water levels (due in particular to decreased winter ice cover allowing more evaporation), increased frequency of intense storm events (altering the timing of inflows), and warmer water temperatures.
Already, Lake Superior has increased water temperatures and an earlier onset of summer stratification by about two weeks in just the past 30 years. Within another 30 years Lake Superior may be mostly ice-free in a typical winter.
Lake Erie water levels, already below average, could drop 4-5 feet by the end of this century, significantly altering shoreline habitat. Climate change could change internal water cycling in the Great Lakes with longer summer stratification potentially leading to larger dead zones (lacking in oxygen). Other potential consequences include less habitat for coldwater fish, more suitable temperatures for aquatic invasive species and hazardous algal blooms, and more mobilization of contaminated sediments as well as nutrients and toxic chemicals from urban and agricultural runoff.
Threats to specific wildlife habitats include:
Conservation Investments to Minimize Climate Change Impacts
Climate change-induced water level declines increase the need to adopt the Great Lakes-St. Lawrence River Basin Water Resources Compact to protect against large-scale out-of-basin diversions, and implement programs to reduce agricultural and urban water use through conservation. As lake levels decline and shoreline wetlands are lost, efforts will be needed to enhance protection, restoration, and development of wetlands at lower water levels to retain their many functions including wildlife habitat and water purification.
The potential for new exotic species to take hold as the water warms could exacerbate an already serious aquatic invasive species problem. Adequate programs to prevent the introduction of new species (e.g., through adequate screening, early detection and rapid response, and treatment protocols) and restrict movement for those invasive species already in the region are essential.
Climate change has the potential to profoundly influence water supply and its quality for the Great Lakes from the surrounding watershed. To maintain healthy lakes it will be important to monitor and manage impacts in the watershed, such as storm surge inputs and erosion. The altering of hydrological cycles by global warming may even require that stormwater and wastewater treatment infrastructures are redesigned or upgraded.
The Great Lakes Regional Collaboration process recommended major restoration of the Great Lakes at a cost of about $20 billion over five years. If implemented, this could result in $80-$100 billion in short and long-term economic benefits to the regional and national economies and is a worthy cause. However, to be effective, these assessments and the restoration efforts must take into account climate change.
Great Lakes Regional Center
Since 1982, the National Wildlife Federation's Great Lakes Regional Center has been a leader in protecting the Great Lakes for the wildlife and humans that depend on this invaluable resource. The Great Lakes Regional Center does important work to protect and improve the area in many ways, with focuses on:
Healing Our Waters-Great Lakes Coalition
Great Lakes Science Center, United States Geological Survey
The Great Lakes, United States Environmental Protection Agency
U.S. Fish & Wildlife Service
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