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Coastal Wetland Monitoring

Since 2011, the Cofrin Center for Biodiversity has participated in the Great Lakes Coastal Wetland Monitoring Program (CWMP), which is funded by the Great Lakes Restoration Initiative issued by the U.S. Environmental Protection Agency’s Great Lakes National Program Office. Coastal wetlands of the Great Lakes support diverse assemblages of plants and animals that have adapted to the dynamic and ever-changing environment of the coastal zone. These coastal wetland systems also provide important ecosystem services, such as controlling shoreline erosion, improving water quality and drinking water, providing flood protection, and offering recreational activities. To better understand these important ecosystems, CWMP field crews collect bird, anuran (frog/toad), plant, fish, and invertebrate data across the U.S. and Canada in Great Lakes coastal wetlands that are at least 4 ha (9.9 ac) in size, dominated by open herbaceous vegetation (e.g., cattail [Typha spp.]), and are connected to and influenced by a Great Lake. The main objectives of the CWMP are to:

  • Monitor and assess Great Lakes coastal wetland health using biotic indicators (birds, anurans, vegetation, invertebrates, and fish)
  • Provide a baseline and method for tracking future changes in plants, animals, and environmental quality.

Over 35 UW-Green Bay students, both undergraduate and graduate, have participated in the surveys, including the completion of two master’s theses (Gaul 2017 and Hohman 2019) and undergraduate projects. Center Director, Dr. Robert Howe, is one of over twenty principal investigators who represent other universities and state and federal agencies across the U.S. and Canada and collaboratively lead this project. Erin Giese, the Center’s Senior Research Specialist, has been coordinating field work for Dr. Howe’s team since the project’s inception. Their student field crews survey for birds and anurans in coastal wetlands as far south as northern Illinois, along the Wisconsin Lake Michigan shoreline, and the southern shoreline of the Upper Peninsula of Michigan along northern Lake Huron. They have visited some of the most pristine wetlands in the entire Great Lakes system including in the far eastern Upper Peninsula in the Munuscong River area.

The CWMP samples over 1,000 coastal wetlands once every five years, though some wetlands are sampled across multiple years. Each year UW-Green Bay field crews establish sampling locations, or “points,” within the wetlands chosen for sampling and survey them for anurans and birds. Certified anuran field technicians conduct 3-minute unlimited-distance point count surveys three times throughout the spring and summer, in which they record all anurans that they hear no matter how far away they are calling. Each of the three seasonal surveys is separated by at least 15 days between early April and mid-July because anurans emerge out of hibernation and become vocal at different times based on overnight temperatures. Certified bird field technicians conduct two 10-minute unlimited-distance point counts between late May and mid-July. One of the two counts is conducted in the early morning, and the second count is done either in the early morning or late evening. During the first 5 minutes of each survey, a technician records all birds seen or heard; then during the second 5-minute period, a broadcast of secretive marsh-nesting bird species is played to elicit feedback from species, such as Least Bittern (Ixobrychus exilis) and Virginia Rail (Rallus limicola), during which the observer continues to record what they see or hear.

Great Lakes water levels fluctuate naturally due to seasonal precipitation, seiche (i.e., a wave that is caused by wind or a change in air pressure leading to a tidal-like effect), storms, and other climatic reasons and can fluctuate by as little as a few centimeters across days or by over a meter across years. In sampling for as many years as they have, the Cofrin Center for Biodiversity and other CWMP field crews have surveyed these plants and animals during significant fluctuations of Great Lakes water levels, including during historic low and high-water levels in the Great Lakes. The Great Lakes experienced record low water levels in 2013 and then record high or near record high levels in 2017-2020. In those few short years, wetlands that previously had a lot of standing emergent vegetation (e.g., cattail, bulrush [Schoenoplectus spp.]) and were relatively shallow quickly became deeper and wetter a few years later when lake levels rose (see air photo examples below of Longtail Point in Brown County, Wisconsin). In some cases, wetlands became completely flooded out without any remaining wetland vegetation. Different communities of birds and anurans utilize these Great Lakes coastal wetlands during different lake levels, as reported by Giese, Howe, and others in their 2018 publication on the bay of Green Bay. For example, Sandhill Crane (Antigone canadensis), Sedge Wren (Cistothorus platensis), and American toad (Anaxyrus americanus) prefer shallower wetlands during lower lake levels, whereas species like Yellow-headed Blackbird (Xanthocephalus xanthocephalus), Sora (Porzana carolina), and northern leopard frog (Lithobates pipiens) prefer deeper wetlands when lake levels are higher. 

2014 aerial view of Brown County Coast; water levels are low
2017 aerial photo of Browny County coast; water levels are higher than in 2014

More exciting results will emerge as field crews continue surveying these dynamic ecosystems and as principal investigators continue analyzing this long-term and rich dataset. To learn more about the CWMP, visit the program’s website at, which also includes detailed protocols, reports, and maps, and read Uzarski et al. (2016)

If you are a student and interested in participating in this project, please contact Erin Giese ( to learn more about how to apply.