LANSING - Long valued for biological diversity and flood control, Great Lakes coastal wetlands are now seen as a tool to suck up and store excess carbon dioxide.
It's an important function as researchers seek to blunt climate change caused by that greenhouse gas.
There are more than 535,000 acres of coastal wetlands in the Great Lakes basin, according to the Great Lakes Coastal Wetlands Consortium.
Nutrients, water and light flowing through these systems fuel a tremendous amount of photosynthesis, a process that absorbs carbon dioxide to produce energy for plant growth, said Donald Uzarski, director of the Institute of Great Lakes Research at Central Michigan University.
Once absorbed, wetlands can store that carbon in soils for centuries, even thousands of years.
"Wetlands are at the top of the list of best systems for sequestering carbon on the landscape," said William Mitsch, a professor emeritus at Ohio State University and director of the Everglades Wetland Research Park at Florida Gulf Coast University.
Carbon sequestration is a natural process where wetlands and other ecosystems capture and store carbon dioxide from the atmosphere.
"The major benefit of wetlands over other environments is that they provide a long term solution for carbon storage where it is kept in the muck of the soil," said Mitsch, who studies wetlands around Lake Erie. "Trees above ground retain carbon for a shorter time in comparison."
Understanding how much carbon dioxide wetlands capture could help focus policy on preserving them to combat climate change.
Wetlands also emit greenhouse gases of their own, most notably methane, which is 25 times more potent than carbon dioxide in terms of its warming effect. But Mitsch says because of how long wetlands can retain carbon, in the long run they act as sinks rather than sources of greenhouse gases.
Mitsch said, "Their capability for sequestering carbon and especially storing it for long durations needs to be better recognized."
Nationally, the U.S. Geological Survey is studying how well all ecosystems store carbon to counterbalance emissions from burning fossil fuels. This congressionally mandated assessment has produced reports on ecosystems in the Great Plains and western U.S.
The latter report concludes that wetlands have the highest carbon capture rate of all ecosystems.
A final report due later this year will assess ecosystem sequestration rates throughout the eastern U.S., including the many coastal wetlands in the Great Lakes.
The studies can help target protection and restoration efforts, said Kristin Bird, a physical scientist at the U.S. Geological Survey in California. "At a regional level, it can provide resource managers the ability to prioritize land in parks and forests for climate change mitigation."
Seeing coastal wetlands as a beneficial tool for society would reflect a change in attitude because they were long regarded as mosquito-infested nuisances or as an obstruction to lake views.
Typically they were dredged and filled, and Central Michigan's Uzarski said that in the Great Lakes, nearly half of coastal wetlands were destroyed in little more than a century for agriculture and development.
"We tend to develop the shoreline and people don't want to live on a coastal wetland, they like to live on a beach or right on the water," Uzarski said. "If you look around Saginaw Bay or Lake Huron, lawns go right to the water's edge."
Bird said coastal development still threatens to destroy and fragment wetlands, not only reducing habitat but also releasing into the atmosphere large amounts of carbon stored in the soils, said Bird.