MI ENVIRONMENT Number of wetland banks in Michigan growing Date: May 13, 2021 , MI Environment looks at Michigan's Wetland Banking Program. The number of public and private wetland bank sites in Michigan has increased by leaps and bounds since the first one was established in 1999, with 42 now in place in all areas of the state. By the end of the year, several more bank sites are expected to be finalized. Wetlands serve as "nature's kidneys" -- absorbing vast amounts of stormwater that would otherwise flood basements and overwhelm sewer systems, providing habitat for wildlife and a nursery for young fish, filtering out pollutants from water as it flows into streams and lakes, and helping control erosion.