NOV. 25, 2025 — A new dataset and updated Environmental Sensitivity Index (ESI) maps are now available for Lake Michigan, providing a critical tool for oil spill preparedness and response in the Great Lakes region. This new Lake Michigan ESI data, which replaces the previous 1993-1994 data, can be downloaded and viewed in Great Lakes ERMA®.

The NOAA Office of Response and Restoration (OR&R)’s ESI program maps sensitive biological and human-use resources, classifies shorelines, and assigns vulnerability rankings based on a shoreline’s sensitivity to oil and chemical spills. These products, in addition to other efforts OR&R is advancing, improve planning and decision-making for environmental response agencies, helping to protect sensitive and rare habitats and inform restoration investments in the Great Lakes.

In addition to the recently published data for Lake Michigan, OR&R has begun updating the ESI datasets for Lakes Superior and Huron, which were last updated in 1994. The updates will also include the Straits of Mackinac and the St. Clair-Detroit River system, last updated in 2019. These areas are high-traffic shipping routes and are home to infrastructure like the 645-mile-long Enbridge Line 5 oil pipeline, which crosses both the Straits of Mackinac and the St. Clair River. Refineries are also located along the St. Clair-Detroit River corridor.

Since 2019, OR&R has released updated ESI data for Lake Erie, the St. Marys River, the St. Lawrence River, the Straits of Mackinac, the St. Clair-Detroit River System, and Lake Ontario. Once all updates are complete, the Great Lakes ESI data will cover over 2,000 miles of shoreline and produce more than 200 maps, improving coastal resilience in the Great Lakes, where busy shipping routes and pipelines support a massive economy. This vital commerce generates $50 billion in annual economic activity, supports between 35 and 40 million tons of cargo, and provides more than 356,000 jobs in the U.S. and Canada.

The modernization of outdated ESI datasets across the Great Lakes has been a collaborative effort supported by significant federal funding. The 2025 update to Lake Michigan data is supported by funding from the Great Lakes Restoration Initiative, in partnership with the Coastal Response Research Center at the University of New Hampshire. Lake Ontario (2023) and the St. Clair/Detroit River System/Straits of Mackinac (2019) updates were funded by the Great Lakes Restoration Initiative, sponsored by the Environmental Protection Agency. The U.S. Coast Guard separately provided funding for the updates to Lake Erie (2022) and the St. Marys and St. Lawrence Rivers (2021).