Via Ducks Unlimited:- "A 2006 study [pdf file at this link] led by Dr. Ned Euliss of the United States Geological Survey Northern Prairie Wildlife Research Center in Jamestown, North Dakota found that wetlands in the Prairie Pothole Region of Canada and the U.S. only comprise approximately 17 percent of the landscape but may sequester twice as much carbon as the surrounding agricultural soils employing no tillage management. Euliss and his co-authors concluded that restoring wetlands on the Prairies may sequester 378 Tg of carbon over a 10-year period and estimated that Prairie wetlands have the potential to offset 2.4 percent of the CO2 emissions produced annually by the burning of fossil fuels in North America at 1990 levels". Ducks Unlimited, indirect source of this information, is the "leading waterfowl and wetlands conservation entity in North America". Their website states that conservation of wetlands is increasingly critical as "the United States is losing more than 80,000 acres of wetland habitat annually. That's more than seven football fields each day!" If you're interested in learning more about DU, look here.
Here are the principal habitats of interest.