Great Lakes ecoregion

This lake system contains the largest supply of freshwater in the world.

During the last ice age, the mile-thick Laurentide ice sheet covered most of Canada and the northern contiguous United States. The massive weight and movement of this glacier gouged out the earth to form the lake basins. About 20,000 years ago, the climate warmed and the ice sheet retreated. Water from the melting glacier filled the basinsoffsite link, forming the Great Lakes. Approximately 3,000 years ago, the Great Lakes reached their present shapes and sizes. Today, the Great Lakes ecoregion contains a variety of habitats, including aquatic, forest, marsh, wetland, and dune ecosystems. Widely varying climate, soils, and topography support more than 3,500 species of plants and animals.

Great Lakes Areas of Concern and NOAA Query Manager sediment sampling stations (orange points) shown in Great Lakes ERMA.
NOAA’s Lake Level Viewer for the Great Lakes
The viewer uses high-resolution elevation data, enabling users to display and visualize water levels associated with different lake level scenarios with a high degree of accuracy.

Humans are also part of the Great Lakes system. Commercial and sport fishing, agriculture, recreation, tourism, manufacturing, and shipping are all important to the region. These activities create jobs and provide goods and services. The fishing industry extracts millions of pounds of fish per year from the lakes. Farmers within this watershed  produce corn, soybeans, hay, milk, and other food products. The area is also known for its industry that produces steel, chemicals, and other products. The shipping opportunities in the Great Lakes played a critical role in settlement of the region and development of industry. Today more than 200 million tons of cargo pass through its waters each year.

Asian carp pose a threat to boater safety, fishing, and ecosystem health. The commercial bait trade remains a potential pathway for Asian carp and other invasive species to spread.
New molecular tool screens bait fish for invasive species risk
One potential pathway for aquatic invasive species introductions is the commercial bait trade; anglers commonly release unused bait fish back into lakes and streams.

Threats to the Great Lakes' ecosystems, include invasive species, climate change, pollution, and habitat destruction. Climate change affects water temperatures, weather patterns, and lake levels. Pollutants from residential, agricultural, and industrial areas reduce water quality. Land development decreases the amount of wildlife habitat. Fish populations have been decliningoffsite link in recent years as a result of these threats and increased fishing pressure.

PHOTO - Great Lakes satellite image from November 2015 with low cloud cover -square
The Great Lakes: A national treasure
In 2010, 16 federal agencies came together to create the the Great Lakes Restoration Initiative. Explore NOAA's work around our splendid Great Lakes, including two case studies of projects that restored habitat, improved water quality, and provided employment.


The Great Lakes Literacy Principles and Fundamental Conceptsoffsite link provide a framework for educators teaching about the Great Lakes, helping teachers and students think about the Great Lakes as a system, rather than a set of unrelated parts. Thinking systemically can provide a greater understanding and help identify solutions to the issues threatening the region.

Updated February 2019