A Glimpse into the Transforming Ecosystem of Florida’s Everglades
Located at the entrance of Florida’s Everglades National Park, across from the Flamingo Visitor’s Center, there once thrived a lush mangrove ecosystem. This area was part of the most extensive mangrove forest in the Western Hemisphere. Today, however, what remains are the skeletal remnants of these mangroves, forming one of the Everglades’ largest ghost forests.
In September 2017, Hurricane Irma struck as a formidable category 4 storm, unleashing violent winds and a powerful storm surge that devastated vast areas of the mangrove forests. Even after seven years, these mangroves show minimal signs of recovery. “At this point, I doubt they’ll recover,” notes David Lagomasino, a coastal studies professor at East Carolina University.
Lagomasino’s presence in the Everglades is part of his fieldwork for NASA’s BlueFlux Campaign. This three-year initiative is dedicated to examining how subtropical wetlands affect atmospheric levels of carbon dioxide (CO2) and methane. Both gases play a significant role in absorbing solar radiation, contributing to the warming of Earth’s atmosphere.
The BlueFlux Campaign is spearheaded by Ben Poulter, a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Poulter’s research focuses on understanding the impact of human activities and climate change on the carbon cycle. As wetland ecosystems respond to rising temperatures, increasing sea levels, and severe weather events, Poulter’s team aims to assess how much carbon dioxide these wetlands can absorb and how much methane they release. The ultimate goal is to develop models that can predict and monitor greenhouse gas concentrations in coastal regions worldwide.
Despite their relatively small coverage, accounting for less than 2% of the Earth’s land-surface area, coastal wetlands play a crucial role in sequestering a significant amount of carbon dioxide. Florida’s coastal wetlands alone are estimated to remove approximately 31.8 million metric tons of carbon dioxide annually. To put this into perspective, a commercial aircraft would need to circle the globe over 26,000 times to emit an equivalent amount of carbon dioxide. Apart from absorbing CO2, coastal wetlands also store carbon in marine sediments. This carbon can remain underground and out of the atmosphere for thousands of years, a phenomenon referred to as blue carbon.
“We’re worried about losing that stored carbon,” Poulter explains. However, he also highlights the opportunity blue carbon presents for climate mitigation, provided that conservation and restoration efforts are backed by robust scientific research.
To delve deeper into this, Lagomasino has been collecting one-meter core samples to analyze historical rates of blue carbon development in mangrove forests. These samples help evaluate how carbon storage rates respond to specific environmental challenges, such as rising sea levels or the increasing frequency of tropical cyclones.
Preliminary data from space-based flux measurements indicate that while tropical wetlands serve as carbon dioxide sinks, they are also significant sources of methane. Methane, a greenhouse gas, traps heat approximately 80 times more effectively than carbon dioxide. Researchers estimate that the methane emissions from Florida’s wetlands could offset the carbon removal benefits by about 5%.
During his recent fieldwork, Lagomasino navigated the Everglades using a small skiff, as many areas are inaccessible by foot. At each research site, he used a metallic peat auger, resembling a giant letter opener, to extract core samples from the soft soil. The Everglades’ peat, composed primarily of carbon-rich, partially decomposed mangrove roots, stems, and leaves, serves as an ideal study subject.
With each sample, Lagomasino employs his body weight to drive the auger into the soil, securing a half-cylinder of earth. These samples are then sealed and sent to the laboratory, where they are sliced into flat discs for age and carbon content analysis.
The rate of peat formation in the Everglades is relatively rapid. In Florida’s mangrove forests, around 2 to 10 millimeters of soil accumulate on the forest floor each year, akin to sand filling an hourglass. Just like ice cores, sediment cores provide a glimpse into Earth’s past. The deeper the core, the further back in time researchers can explore. By examining the soil’s contents, scientists can glean insights into the climate conditions prevalent when the soil was formed.
In parts of the Everglades, soil deposits can reach depths of up to 3 meters (approximately 10 feet), with one meter potentially representing close to 100 years of peat accumulation. In contrast, similarly sized deposits in the Amazon rainforest may take over 1,000 years to develop. This difference underscores the potential for restoring peat losses in coastal wetlands significantly faster than in other forest types.
“There are also significant differences in fluxes between healthy and degraded mangroves,” says Lola Fatoyinbo, a research scientist at NASA’s Goddard Space Flight Center. In areas where mangrove forests have suffered, such as post-hurricane, the release of greenhouse gases into the atmosphere increases. As wetland ecology adapts to mounting natural and human pressures, the data produced will enable researchers to accurately monitor the impact of ecological changes on global carbon dioxide and methane levels.
Understanding Wetland Methane: A Potent Greenhouse Gas
Methane is naturally produced by microbes inhabiting wetland soils. However, changes in wetland conditions can accelerate the growth rate of these methane-producing microbes, leading to increased atmospheric methane emissions.
Methane is notably more potent than carbon dioxide as a greenhouse gas, with a warming potential 84 times greater over a 25-year period. As a result, methane emissions can offset some of the benefits that blue carbon ecosystems offer as natural carbon dioxide sinks.
While Lagomasino focuses on soil studies to comprehend long-term greenhouse gas storage, Lola Fatoyinbo and Peter Raymond, an ecologist at Yale University’s School of the Environment, measure how these gases are exchanged between wetland vegetation and the atmosphere. This measurement is known as gaseous flux.
To measure flux, scientists use chambers that neatly adhere to areas with significant gas exchange rates. Box-like chambers are secured to above-ground roots and branches, while domed chambers measure gas escaping from the forest floor. The concentration of gases within each chamber is recorded over time.
Generally, as wetland health declines, less carbon dioxide is absorbed, and more methane is emitted. However, the precise relationship between wetland health and gaseous flux remains poorly understood. Questions arise, such as what flux looks like in ghost forests, and how subtle changes in variables like canopy coverage or species distribution affect carbon dioxide sequestration or methane production.
“We’re especially interested in the methane part,” Fatoyinbo states. “It’s the least understood, and there’s a lot more of it than we previously thought.”
Based on data gathered during BlueFlux fieldwork, Poulter highlights that “coastal wetlands remove massive amounts of carbon dioxide and produce substantial amounts of methane. But overall, these ecosystems appear to provide a net climate benefit, removing more greenhouse gases than they produce.” This balance could shift as Florida’s wetlands continue to respond to ongoing climate disturbances.
The Future of South Florida’s Ecology
Florida’s wetlands have existed for around 5,000 years. However, in the past century alone, more than half of the state’s original wetlands have been lost due to vegetation clearance and water drainage to accommodate the growing population. The Everglades system now retains 65% less peat and 77% less stored carbon than it did before drainage. The future of this ecosystem, which not only serves as a significant carbon reservoir but also supplies drinking water for over 7 million Floridians and sustains unique flora and fauna, remains uncertain.
Nevertheless, scientists dedicated to understanding and restoring South Florida’s ecology remain optimistic. “Nature and people can coexist,” asserts Meenakshi Chabba, an ecologist and resilience scientist at the Everglades Foundation in Miami-Dade County, Florida. “But we need good science and good management to reach that goal.”
NASA’s BlueFlux campaign’s next phase involves developing a satellite-based data product to assist regional stakeholders in assessing, in real-time, how Florida’s wetlands are responding to restoration efforts aimed at safeguarding one of the state’s most treasured natural resources and the communities dependent on it.
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