There is no place like a marsh in the dog days of summer. Dense patches of cattails sway like waves in the breeze, a breeze carries the trilling of a red-winged blackbird and the aroma of blossoming milkweed. In the golden light, a jewel-toned dragonfly speeds through the air with the agility of a fighter pilot. 

Marshes, swamps, bogs, fens: no matter what you call them, wetlands – places where the ground is saturated with water for most or all of the year – are critically important for a variety of plant and animal species, including many that are threatened or endangered. Coastal wetlands in particular serve as important nursery and foraging habitats for many fish species, but they are also among the most vulnerable ecosystems globally to human-caused changes¹.

When you hear the phrase “coastal wetland,” you might think of mangroves or salt marshes at the edge of the ocean, but there are also freshwater coastal wetlands! For example, wetlands that are directly connected to the waters of the North American Great Lakes are also considered “coastal”, and like their marine counterparts, they provide a ton of benefits for humans (also called ecosystem services). Coastal wetlands protect shorelines from erosion, prevent flooding by retaining excess water during storms and releasing it slowly over time – basically like giant sponges – and act as the planet’s kidneys, filtering runoff from the surrounding land and improving downstream water quality.  

Like coral reefs and rainforests, Great Lakes coastal wetlands teem with life, including many fish species that are recreationally important. Many Great Lakes fish species depend on coastal wetlands at some point during their life cycles, with species such as Northern Pike (Esox lucius), Yellow Perch (Perca flavescens), and Largemouth Bass (Micropterus salmoides) relying on these habitats when they are young².

Although they make up a small fraction of the lakes’ surface areas, Great Lakes coastal wetlands often face the highest number of stressors because they represent the primary interface with humans³. Over half of historic coastal wetland area has been lost since European settlement of the Great Lakes basin⁴, and while the rate of loss has slowed due to state and national protection measures, new threats such as non-native species and climate change threaten remaining wetlands. Not to mention, many of the most pressing environmental challenges facing the Great Lakes – water quality concerns, decreasing fisheries, and increased flooding – are tied to the historic decline in coastal wetland area. To combat these challenges and maintain the benefits wetlands provide, it’s critical to make sure remaining habitats are in good shape.

Enter: the Great Lakes Coastal Wetland Monitoring Program (CWMP), a binational collaboration of U.S. and Canadian groups including federal agencies, states, and universities working together in a standardized way to monitor the health of coastal wetlands throughout the Great Lakes basin⁵. With funding from the Great Lakes Restoration Initiative, this group has sampled over 1,000 coastal wetlands since the program began in 2011. When CWMP crews visit a wetland, they give the whole ecosystem a “check-up” by taking measurements of water quality parameters including dissolved nutrient concentrations (like nitrogen and phosphorus) as well as doing surveys of invertebrate, fish, amphibian, and bird communities.

CWMP provides baseline information about the health of coastal wetland ecosystems that can indicate human impacts over time such as changes to water quality resulting from human land use⁶. Additionally, CWMP surveys have revealed new locations of non-native species such as the New Zealand mud snail (Potamopyrgus antipodarum). The collected data help managers make informed decisions about how to prioritize protection and restoration efforts. A manager can use the program’s online mapping tool to select a specific wetland and see reports from every sampling event.

By monitoring coastal wetlands, scientists are not only working to keep a finger on the pulse of these unique and globally important ecosystems, but also to ensure that future generations can enjoy a summer’s day in the marsh.

References

1. Zedler, J.B., & Kercher, S. (2005). Wetland resources: status, trends, ecosystem services, and restorability. Annu. Rev. Environ. Resour., 30, 39-74. https://doi.org/10.1146/annurev.energy.30.050504.144248  
2. Jude, D.J., & Pappas, J. (1992). Fish utilization of Great Lakes coastal wetlands. Journal of Great Lakes Research, 18(4), 651-672. https://doi.org/10.1016/S0380-1330(92)71328-8 
3. Allan, J.D., et al. (2013). Joint analysis of stressors and ecosystem services to enhance restoration effectiveness. Proceedings of the National Academy of Sciences, 110(1):372–377. https://doi.org/10.1073/pnas.1213841110 
4. Brazner, J., et al. (2000). Assessing the ecological importance of coastal wetlands in a large lake context. Internationale Vereinigung für theoretische und angewandte Limnologie: Verhandlungen, 27. 1950-1961. https://doi.org/10.1080/03680770.1998.11901583
5. Uzarski D.G., et al. (2017). Standardized measures of coastal wetland condition: implementation at a Laurentian Great Lakes basin-wide scale. Wetlands, 37:15–32. https://doi.org/10.1007/s13157-016-0835-7
6. Harrison, A.M., et al. (2020). A basin-wide survey of coastal wetlands of the Laurentian Great Lakes: development and comparison of water quality indices. Wetlands, 40(3), 465-477. https://doi.org/10.1007/s13157-019-01198-z