The Great Lakes Areas of Concern are specific areas 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 system of freshwater lakes in the world and are shared between 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 total is longer than the combined coastlines of the contiguous United States along the Pacific and Atlantic Oceans. The lakes are used for moving goods and people, as well as for recreational activities.

Description of an area of concern

An area of concern must have at least one problem that affects how the water is used. This means the water has changed in its chemical, physical, or biological condition. These problems include:

• Limits on eating fish and wildlife
• Fish and wildlife tasting bad
• Fewer fish and wildlife
• Fish with tumors or other physical issues
• Birds or animals with physical issues or trouble having babies
• Damage to bottom-dwelling organisms
• Limits on digging or removing material from the water
• Too much algae growth or algae that is not wanted
• Limits on using water for drinking or water that tastes or smells bad
• Beaches being closed to the public
• Damage to the beauty of the water area
• Extra costs for farming or businesses
• 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 that do not meet the goals of the agreement and where problems have caused or could cause harm to the ability of the area to support aquatic life." This agreement includes rules and groups that decide if an area should be labeled as an Area of Concern. The purpose of the agreement is to improve and protect the chemical, physical, and biological health of the Great Lakes Basin ecosystem by taking focused actions aimed at these Areas of Concern. Each waterway has unique features that have led to environmental harm, so a Remedial Action Plan has been created to find the causes of the harm and guide local efforts to fix the waterways. The goal of each Remedial Action Plan is to remove the waterway from the list of Areas of Concern.

Since the agreement was first created in 1972, it has been updated several times to include actions that prevent human-related problems. The most recent update in 2012 added new steps to address issues that appeared after the 1987 update. This update also invited more groups to help shape policies and solutions. Led mainly by the U.S. Environmental Protection Agency and Environment and Climate Change Canada, the Great Lakes Committee now includes representatives from Indigenous communities and local government groups. This ensures that local perspectives are considered in all efforts to fix problems. This group is also called the Binational Executive Committee (BEC), which meets at least twice a year to set goals and check progress. Under the GLWQA, specific plans have been created to address problems in certain lakes. For example, the 2012 update led to the creation of the GLWQA Nutrients Annex Subcommittee to help reduce algal blooms in Lake Erie. Overall, the Great Lakes Water Quality Agreement is a flexible law that continues to adapt to new challenges and priorities.

Other laws and policies

The United States, Canada, and the states that border the Great Lakes have made many laws, policies, and groups to help keep the Great Lakes clean and free from pollution. In 1909, the Boundary Waters Treaty was created to manage water quality in the Boundary Waters, which are shared by the U.S. and Canada. This treaty led to the formation of the International Joint Commission to handle its 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 proposed as a cooperative agreement. This agreement aimed to use the ecosystem as a way to manage the Great Lakes. The Air Quality Agreement was established to protect the health of both the Great Lakes ecosystems and the people living nearby. It limits the release of harmful chemicals. Another policy, the Great Lakes Binational Toxics Strategy, was introduced in 1997 to control long-lasting toxic substances that build up in the environment over time, such as DDT, PCBs, mercury, and dioxins. These toxins remain in ecosystems for a long time and can seriously harm plants and animals.

Threats

One of the important issues affecting the Great Lakes is the number of non-native species that are invading the lakes. About every eight months, a new species enters the Great Lakes, causing serious harm to the ecosystems in the area. When new animals or insects move into or leave an ecosystem, they can cause damage similar to that caused by pollution.

A key food source for many fish in Lake Michigan was the Diporeia shrimp. These shrimp have dropped sharply due to an infestation of zebra mussels. The number of Diporeia shrimp has decreased from more than 10,000 per square meter to nearly zero on the lake bottom because of these mussels. In Lake Michigan, the Diporeia population has declined by 94% over the past ten years. In its neighboring lake, Lake Huron, the Diporeia population has dropped by 57% in just three years. This problem is also seen in other 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 species, disrupt the food web, threaten human health, and negatively affect the economy by damaging fisheries, agriculture, and tourism.

Point-source pollution happens when pollutants enter a waterway directly, such as from municipal sewage or industrial wastewater. Before the 1972 Clean Water Act in the United States and similar laws in Canada, cities, industries, farms, and other facilities often released wastewater into lakes, rivers, and other waterways, believing that diluting the waste in water would reduce harm. Later studies showed this belief was often wrong. Over many years, this practice led to contamination of waterways with chemicals, mining waste, and human waste.

Nonpoint source pollution occurs when runoff from streets, lawns, farms, and other areas carries toxins, chemicals, and eroded soil into lakes, rivers, and oceans. This type of pollution is considered the most difficult to address because it is hard to trace and regulate. Many experts believe nonpoint source pollution is the biggest challenge for the Great Lakes. As urban areas grow, this pollution has harmed lakes by causing excessive plant and algae growth from fertilizer runoff, which harms fish and other aquatic life.

Atmospheric pollution is pollution that falls from the sky and settles into water sources, such as lakes, rivers, and oceans. Sources include smoke stacks from power plants and factories, as well as cars, trucks, and other vehicles that burn fossil fuels. This pollution often travels 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 washing aluminum from soil into streams and lakes. While some plants and animals can survive in acidic conditions, others cannot, leading to their decline. Burning coal and other fossil fuels is a major cause of acid rain.

List of areas of concern

As of August 2021, 11 former areas of concern have 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)

Additionally, eight areas of concern in the United States and two in Canada have finished restoration work and are waiting for final removal from the list.