About - State of the Great Lakes

Why are the Great Lakes important?

The Great Lakes contain one-fifth of the world’s fresh surface water supply and together are one of the largest freshwater ecosystems on Earth, supporting rare and globally unique species. They provide a source of drinking water to approximately 20 million Americans and 10 million Canadians and are important to the economies of both Canada and the United States, supporting manufacturing, transportation, farming, tourism, recreation, energy production and other forms of economic growth. To the Indigenous communities around the basin, the Great Lakes waters, plants and wildlife provide a continuation of lifeways and a sense of identity.

How are governments working together to protect the Great Lakes?

The Great Lakes Water Quality Agreement, signed by the Governments of Canada and the United States, commits both countries to work cooperatively to restore and protect the water quality and ecosystem health of the Great Lakes. Canada and the United States work with Tribes, First Nations, Métis, provincial, state and municipal governments, watershed management agencies, other local public agencies, industry and the public to sustain a healthy Great Lakes ecosystem for the benefit of present and future generations of Canadians and Americans. For over half a century, the two countries and their many Agreement partners have worked together to protect this valuable resource.

How is the health of the Great Lakes assessed?

The Governments of Canada and the United States, together with their many Agreement partners, assess the overall health of the Great Lakes using a suite of ecosystem indicators. The indicators of ecosystem health are aligned with the General Objectives of the Great Lakes Water Quality Agreement. For this report, the nine indicators are supported by 42 sub-indicators with input from over 200 experts who contributed, analyzed, and reviewed available data to reach consensus on the current assessments. Data for most sub-indicators includes information current to 2022 or 2023. Status assessments* are generally described in terms of Good, Fair, or Poor conditions. Trends* are typically described as Improving, Unchanging, No Trend, or Deteriorating and are generally assessed over a 10-year period. Refer to the State of the Great Lakes 2025 sub-indicator reports.

What is assessed and how is the Great Lakes assessment used?

The suite of Great Lakes indicators focuses on the basin-wide assessments that include offshore or open water conditions, with some nearshore or land-based stresses included where they have an impact on the offshore water quality of the Great Lakes. The indicators are not designed to assess regional or local conditions. Great Lakes indicator assessments help governments identify current and emerging challenges to Great Lakes water quality and ecosystem health. Indicator assessments also help governments evaluate the effectiveness of environmental programs and policies in place to address challenges and identify priorities. In addition, indicator assessments help inform and engage other stakeholders, including the public, and provide information that in turn supports efforts to restore and protect the Great Lakes.

2025 Assessment of the nine Great Lakes indicators of ecosystem health

Great Lakes Indicator	2025 Assessments: Status and Trend
Drinking Water	Status: Good Trend: Unchanging
Beaches	Status: Good Trend: Unchanging
Fish Consumption	Status: Fair Trend: Improving
Toxic Chemicals	Status: Fair Trend: Unchanging to Improving
Habitat and Species	Status: Fair Trend: Unchanging
Nutrients and Algae	Status: Poor to Fair Trend: Unchanging
Invasive Species	(Prevention) Status: Good Trend: No Trend
Invasive Species	(Impact) Status: Poor Trend: No Trend
Groundwater	Status: Good Trend: Undetermined
Watershed Impacts and Changes in Physical Conditions	(Watershed Impacts) Status: Fair Trend: No Trend
	Changes in Physical Conditions: No Overall Assessment

Impacts of Changing Physical Conditions in the Great Lakes

Changing physical conditions, such as warming waters, reduced ice cover, and altered precipitation patterns, can impact nutrient delivery and habitat quality. As changes are observed in the Great Lakes ecosystem, basin-wide and lake assessments remain critical to assess the impacts of these changes in order to protect and restore the Great Lakes.

Definitions

Status

Status* terms are generally defined as:

Good: Most or all ecosystem components are in acceptable condition.

Fair: Some ecosystem components are in acceptable condition.

Poor: Very few or no ecosystem components are in acceptable condition.

Undetermined: Data are not available or are insufficient to assess the condition of the ecosystem components.

Trend

Trend* terms are generally defined as:

Improving: Metrics show a change toward more acceptable conditions.

Unchanging: Metrics generally show no overall change in condition.

No Trend: Data are available, but the trend is not statistically improving or deteriorating due to high variability in the data, or multiple measured parameters are changing in different directions. No Trend is different from Unchanging (which is used when the trend is not statistically significant and has low variability (i.e., stable)) and Undetermined (which should be reserved for cases where data availability is limited).

Deteriorating: Metrics show a change away from acceptable condition.

Undetermined: A sufficient amount of data are not available to report on a trend.

*see individual sub-indicator reports for more detail on Status and Trend definitions.

Participating Organizations

Many partners assisted with the development of the State of the Great Lakes 2025 Report. Thank you to the authors and task team members from the organizations listed below for their hard work and continued support.

Agriculture and Agri-Food Canada
Birds Canada
Canada Water Agency
Central Michigan University
Conservation Ontario
Cornell University
Environment and Climate Change Canada
Essex Region Conservation Authority
Fisheries and Oceans Canada
General Dynamics Information Technology
Great Lakes Fishery Commission
Great Lakes Indian Fish & Wildlife Commission
Health Canada
Indiana Department of Environmental Management
Indiana University
International Joint Commission
LimnoTech
Little Traverse Bay Bands of Odawa Indians
Michigan Department of Environment, Great Lakes,
and Energy
Michigan Department of Natural Resources
Michigan Technological Research Institute
National Oceanic and Atmospheric Administration

Natural Resources Canada
Ohio Lake Erie Commission
Ontario Ministry of Natural Resources
Ontario Ministry of the Environment, Conservation
and Parks
Oregon State University
Pennsylvania Fish and Boat Commission
SUNY Brockport
SUNY Buffalo State
U.S. Army Corps of Engineers
U.S. Environmental Protection Agency
U.S. Fish and Wildlife Service
U.S. Geological Survey
University of Minnesota – Natural Resources Research
Institute
University of Wisconsin, Green Bay
University of Wisconsin, Milwaukee
University of Wisconsin, Superior