The Great Lakes Areas of Concern are specific regions within the Great Lakes Basin that have serious environmental problems. There are 43 such areas in total, with 26 located in the United States, 12 in Canada, and five shared by both countries.

The Great Lakes are the largest group of freshwater lakes in the world and are shared by the United States and Canada. They hold 95% of the surface freshwater in the contiguous United States and have 10,000 miles of coastline, including connecting channels, mainland, and islands. This coastline is longer than the combined coastlines of the Pacific and Atlantic Oceans in the contiguous United States. The lakes are used for transportation and shipping and also serve as places for recreation.

Description of an area of concern

An area of concern must show at least one harmful effect on how water is used, which means the water has changed in its chemical, physical, or living parts. These effects include:

• Rules about eating fish and wildlife
• Bad taste in fish and wildlife
• Fewer fish and wildlife
• Abnormal growths or shapes in fish
• Abnormal growths or problems with reproduction in birds or animals
• Damage to bottom-dwelling creatures
• Rules against digging or moving soil in water areas
• Too much algae growth or unwanted algae
• Rules about drinking water or problems with taste and smell
• Closing beaches for safety
• Worse-looking water areas
• Higher costs for farming or industry
• Damage to tiny water plants and animals
• Loss of homes for fish and wildlife

The Great Lakes Water Quality Agreement

The Great Lakes Water Quality Agreement (GLWQA) between the United States and Canada defines "Areas of Concern" as places where water quality is poor enough to harm the ability of the area to support aquatic life. This agreement outlines the rules and processes used to determine if an area should be labeled as an Area of Concern. The goal of the agreement is to improve and protect the chemical, physical, and biological health of the Great Lakes Basin ecosystem by taking specific actions aimed at fixing problems in these Areas of Concern. Each waterway has unique conditions that have caused its environmental issues, so a Remedial Action Plan is created to identify the causes of these problems and guide efforts to restore the waterway. The purpose of each Remedial Action Plan is to remove the waterway from the list of Areas of Concern once it is fully restored.

Since the GLWQA was first created in 1972, it has been updated several times to address new human-caused challenges. The most recent update in 2012 added new rules to handle problems that have developed since the last update in 1987. This update also invited more groups to help shape policies and improve water quality. The agreement is mainly managed by the U.S. Environmental Protection Agency and Environment and Climate Change Canada. The Great Lakes Committee, also known as the Binational Executive Committee (BEC), includes representatives from Indigenous communities and local governments. This group meets at least twice a year to set goals and review progress. Under the GLWQA, specific plans have been created to address issues in certain lakes. For example, the 2012 update led to the creation of the GLWQA Nutrients Annex Subcommittee, which focuses on reducing algal blooms in Lake Erie. The Great Lakes Water Quality Agreement is an ongoing effort that continues to adapt to new challenges and priorities.

Other laws and policies

The United States, Canada, and the states surrounding the Great Lakes have developed many laws, policies, and groups to help keep the Great Lakes clean and free from pollution. In 1909, the Boundary Waters Treaty was established to manage water quality in the shared waters between the U.S. and Canada. This led to the creation of the International Joint Commission to handle the treaty's responsibilities. When sea lamprey populations grew rapidly in the Great Lakes, the Great Lakes Fishery Commission was formed to address the problem. In 1994, the Ecosystem Charter for the Great Lakes–St. Lawrence Basin was introduced as a cooperative agreement. This agreement focused on managing the Great Lakes by considering the entire ecosystem. The Air Quality Agreement was created to protect both the ecosystems of the Great Lakes and the people who live nearby. It limits the release of harmful chemicals into the air. In 1997, the Great Lakes Binational Toxics Strategy was developed to control toxic substances that remain in the environment for long periods, such as DDT, PCBs, mercury, and dioxins. These substances can harm plants, animals, and ecosystems even after they are no longer present in the area.

Threats

One of the main issues in the Great Lakes is the large number of non-native species that are taking over the area. About every eight months, a new non-native species enters the lakes, causing serious harm to the ecosystems. When new animals or insects enter or leave an ecosystem, it can be just as harmful as pollution.

A key food source for many fish in Lake Michigan was Diporeia shrimp. These shrimp have decreased greatly because of an infestation of zebra mussels. The number of Diporeia shrimp has dropped from over 10,000 per square meter to nearly zero on the lake bottom due to these mussels. In Lake Michigan, the Diporeia population has declined by 94% over the past ten years. In its neighboring lake, Lake Huron, the population has decreased by 57% in just three years. Similar problems are found in all the Great Lakes.

The Great Lakes have been harmed by more than 180 invasive and non-native species. Examples include zebra mussels, quagga mussels, round gobies, sea lampreys, and alewives. Invasive plants include purple loosestrife and Eurasian watermilfoil. These species harm native plants and animals, disrupt the food web, and affect human health. They also hurt the economy by damaging fisheries, agriculture, and tourism.

Point-source pollution happens when pollutants enter water directly, such as from sewage or industrial wastewater. Before the 1972 Clean Water Act in the United States and similar laws in Canada, many cities, industries, and farms released wastewater into lakes and rivers, believing that diluting the waste would reduce harm. Later research showed this belief was often wrong. Over time, many waterways became polluted with chemicals, mining waste, and human waste.

Nonpoint-source pollution occurs when rainwater or runoff from streets, lawns, farms, and other areas carries toxins, chemicals, and soil into lakes, rivers, and oceans. This type of pollution is hard to control and trace because it comes from many different places. Experts say nonpoint-source pollution is the biggest problem for the Great Lakes. As urban areas grow, lakes that once had balanced ecosystems are now filled with too much plant and algae growth, caused by excess fertilizer from lawns and farms. This growth harms fish and other aquatic life.

Atmospheric pollution is pollution that falls from the air into water and soil. Sources include smoke from power plants, factories, cars, trucks, and engines that burn fossil fuels. This pollution can travel hundreds of miles from its source, making it hard to track. It is a major cause of pollution in the Great Lakes and water bodies worldwide. Acid rain, a type of atmospheric pollution, forms when chemicals like sulfur dioxide and nitrogen oxides mix with water, oxygen, and other chemicals in the air. Acid rain harms aquatic ecosystems by releasing aluminum from soil into water. Some plants and animals can survive acid rain and aluminum, but others cannot. Burning coal and other fossil fuels is a major cause of acid rain.

List of areas of concern

By August 2021, 11 previously identified areas of concern had been completely restored and removed from the list. These areas include:

• Oswego River (2006)
• Presque Isle Bay (2013)
• Deer Lake (2014)
• White Lake (2014)
• Lower Menominee (2020)
• Ashtabula River (2021)
• Rochester Embayment (2024)
• Muskegon Lake (2025)
• Collingwood Harbour (1994)
• Severn Sound (2002)
• Wheatley Harbour (2010)

In addition, eight areas of concern in the United States and two in Canada have finished their restoration work and are waiting for final approval to be removed from the list.