The researchers have predicted that both wetlands' ability to sequester carbon in their soil will increase at a steady pace through year 50. At the 15-year mark, these two wetlands were sequestering carbon about 40 percent faster than was a similar reference natural wetland 200 grams of carbon per square meter per year vs. 140 grams of carbon per square meter per year. This could be because of the high biomass production in the created wetlands, Mitsch said.
Though almost all freshwater wetlands are known to release methane, a greenhouse gas, into the atmosphere, Mitsch asserts that wetlands are valuable carbon dioxide sinks and that more than compensates for the methane emissions. Methane oxidizes in the atmosphere while carbon dioxide does not, tipping the balance of value for protection against greenhouse gases in favor of wetlands because of their carbon storage capacity, he said.
"I think wetlands' value as carbon sinks is gigantic, but it is still under-appreciated," Mitsch said. "This study and other work we've done suggests that wetlands can be cost-effective tools to reduce the effects of carbon emissions while they perform their other ecosystem functions, such as water quality improvement and flood control."
The Ohio State wetlands tell a different tale about their ability to retain nutrients, which helps prevent certain substances from fouling adjacent bodies of water.
Phosphorus is problematic in inland freshwater systems, where, in excess, it can stimulate the growth of algae. The experimental wetlands at Ohio State started strong at retaining phosphorus, but the retention rate has declined over time, from 60 percent to 10 percent over the course of the 15 years of study.
For nitrates, which can lead to algae blooms and kill some fish species in coas
|Contact: William Mitsch|
Ohio State University