The Florida Everglades is a complicated climate actor. The 1.5-million-acre wetland system remains a carbon sink, removing an average of 13.7 million metric tons of carbon dioxide from the atmosphere each year, but the system also releases methane. In a new study, Yale School of the Environment scientists analyzed the greenhouse gas fluxes in its mangroves and fresh-water marshes, providing a more detailed approach for guiding restoration efforts
The study, published in the Proceeding of the National Academy of Sciences (PNAS) , found that between 2003-2020, the Everglades increased carbon capture by 18%, with saltwater mangroves having the greatest capacity to capture carbon. Only about 16% of the carbon dioxide captured was offset by methane emissions in the mangroves. In freshwater marshes, almost 82% of carbon dioxide captured was offset by net methane emissions.
Methane accounts for 30% of the warming since industrialization. It traps over 80 times more heat than carbon dioxide over a 20-year period.
"While different wetland types vary in how they capture and release greenhouse gases, the study confirms that the Everglades continues to function as a major carbon sink. This diversity offers important insights for strengthening climate resilience and guiding restoration efforts," said Sparkle Malone , assistant professor of ecosystem carbon capture, and coauthor of the study.
Wetlands must be understood as integrated systems, in which carbon dioxide uptake and methane emissions interact in complex yet manageable ways, she said.
"Freshwater marshes, while associated with higher methane emissions, remain invaluable. They play a critical role in flood control, water filtration, habitat provision, and carbon storage. Rather than diminishing the Everglades' climate value, the findings provide a roadmap for maximizing it," Malone said.
The study investigated fluctuations in wetland carbon exchange rates in blue carbon ecosystems, which include the coastal saline mangroves and marshes, and teal carbon ecosystems, which are made up of non-tidal freshwater marshes and forests in the Everglades.
The team used measurements from the Coastal Everglades Ameriflux towers to understand carbon exchange rates within the Everglades National Park and Big Cypress National Preserve in southern Florida between 2000 and 2024. They also reviewed atmospheric carbon measurements above Everglades study sites collected by NASA by plane between 2022 and 2024 and satellite data that measured vegetation changes across the study area. By combining satellite, tower, and flight data, the team created a model that can estimate fluctuations in carbon exchange.
"This sort of broad collaboration between government agencies and academics combining long-term monitoring data with cutting-edge methods is necessary to understand complex and important ecosystems like the Florida Everglades," said Peter Raymond , the Oastler Professor of Biogeochemistry and co-director of the Yale Center for Natural Carbon Capture., who coauthored the study.
By identifying the conditions under which ecosystems capture and store carbon most efficiently land managers can prioritize protection and restoration efforts that enhance the region's overall climate benefits, the researchers noted. Protecting mangroves from hydrologic disruption and storm damage, for example, helps preserve one of the most effective natural carbon sinks on Earth.
"Our work shows that you can't consider carbon dioxide or methane in isolation," said doctoral candidate Jonathan Gewirtzman '23 MPhil, who coauthored the study. "We really have to understand the balance of ecological processes, and this information can inform better decisions."
