Will Turning Wetlands Into Condos Kill Us All?

Wetlands naturally sequester carbon. Draining them is a big eco-no-no.

An emergent marsh in Morgan City, Louisiana. (Photo: Sean Gardner / Reuters)
The director of the Public Trust Project, Alison has written for Grist and Politics Daily, among others.

Drained wetlands in Sweden emit as much greenhouse gas as Swedish industry, new research shows.  

The Swedish Environmental Protection Agency commissioned scientists at two universities to analyze the scale of carbon emissions given off by agricultural lands and forests that were once wetlands.

The researchers found that these drained wetlands, which comprise 10 percent of the country’s surface area, are a significant source of harmful emissions.

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Wetlands are areas of land that flood periodically, like marshes, bogs, and swamps, which create distinct ecosystems with rich soil that supports aquatic plants. When wetlands are drained or degraded because of agriculture, forestry, or oil and gas development, they can emit carbon dioxide and nitrous oxide into the atmosphere. 

“As long as wetlands remain wet, only methane is given off,” lead researcher Dr. Asa Kasimir Klemedtsson, from the Department of Earth Sciences at the University of Gothenburg, said in a press release about her findings.

“When they are not being drained, wetlands are really good at taking carbon out of the air and putting it in the ground where it is not aggravating the greenhouse effect and changing the climate,” said Scott Eustis, coastal wetlands specialist at the Gulf Restoration Network, an organization working to protect Louisiana’s wetlands from development, pollution, and damages from the oil and gas industries.

Wetlands are found on every continent except Antarctica. In the continental U.S., there are 105 million acres of wetlands, according to the U.S. Fish and Wildlife Service.

But wetlands have been disappearing for centuries, largely because of human activities like dredging, draining, and logging, as well as sea level rise and erosion. Since the 1600s, the U.S. has lost half of its original wetlands.

A full 40 percent of the country’s remaining wetlands are located in the state of Louisiana. But decades of oil and gas development have destroyed between 250,000 and 400,000 acres of the state’s marsh wetlands. The Mississippi River Delta loses the equivalent of a football field of marshland every hour due to erosion.

“The loss of wetlands has created a number of problems, one of which is that it’s made our interior areas in Louisiana, like New Orleans, very vulnerable to hurricane surges,” Eustis said. “We saw this in Hurricane Katrina in 2005, and it has been an ongoing problem every year. Before we lost these wetlands, hurricanes happened but they weren’t so much of a threat. Now these storms are life threatening, and threatening to our coastal infrastructure and industry.” 

Every 2.7 miles of wetlands can absorb an average of one foot of storm surge, according to a Louisiana government website, as well as a significant amount of carbon.

Exactly how much carbon wetlands can store is an important calculation—and until recently, a challenging one, too. Just this year, an environmental consulting company called Tierra Resources released a proposed methodology for measuring how much carbon the Delta wetlands could sequester if they were restored, and what economic benefit that restoration would bring to the region—just the opposite of the question posed by Swedish researchers.

Sarah Mack, a consultant with Tierra Resources, told the New York Times that her research showed that some forest projects could absorb between five and 40 tons per acre per year, for decades.

But altering the course of wetland loss is slow-going. Although coastal wetland restoration efforts have been ongoing for more than two decades, "not a single project capable of reversing the trend awaits approval [by the government]," according to the New Orleans Times-Picayune. Unless significant restoration is undertaken, Louisiana's marsh wetlands will be gone by 2040—signalling disaster for coastal areas and the industries they support.

“There’s a lot of discussion after [Hurricane] Sandy, about whether New York needs a large flood barrier,” Eustis said. “In Louisiana, we need to restore the natural environment as part of our flood defense.” 

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