Two dedicated scientists found themselves in a tricky situation, their boat bogged down in a Louisiana swamp. As they strained to push it free with a metal pole and a paddle, the disturbed mud released a stream of bubbles.
“That’s methane!” exclaimed Gage Hunter, a graduate student, identifying the potent greenhouse gas escaping from the murky depths.
Hunter and postdoctoral researcher Manab Dutta were on a crucial mission in this New Orleans-area wildlife reserve: to track methane, a powerful heat-trapping gas generated by local bacteria.
While industrial sources like gas and oil operations are well-known for methane leaks, there’s growing alarm about the escalating emissions from natural ecosystems, particularly wetlands.
Annually, wetlands are estimated to release a staggering 180 to 400 million metric tons of methane, significantly more than the 120 to 133 million metric tons from fossil fuel industries and coal mining. This information comes from the Global Methane Budget, a continually updated scientific assessment. Methane forms in waterlogged, oxygen-deprived soils and is then released into the atmosphere through bubbles, decaying organic matter, and certain plants. A warmer planet accelerates these microbial processes, leading to an even faster release of methane from wetlands globally.
From the vast Everglades to the dense Amazon, researchers worldwide are dedicated to pinpointing the precise quantities of methane wetlands generate and the environmental conditions that influence these emissions.
Video: Scientists navigate a narrow waterway in the Luling, Louisiana swamp, a crucial research area near the Mississippi River.
Dr. Dutta skillfully steers the research boat through the swamp, heading towards a designated study area.
Understanding methane’s complete cycle is urgent because, in the short term, it’s 80 times more potent than carbon dioxide as a heat-trapping gas. It’s already responsible for approximately 30% of global temperature increases since the Industrial Revolution.
Hunter investigates both types of bacteria: those that produce methane and those that consume it. The critical distinction lies in the net amount of methane released into the atmosphere.
“We’re the ground team, focused on deciphering the methane dynamics within the soil,” explained Hunter, a student in Louisiana State University’s oceanography and coastal sciences department. “We leave the atmospheric measurements to others.”
Images: Scientists meticulously record the depth of swamp samples, prepare specialized domes for gas collection, and analyze sediment slurries in a Baton Rouge lab.
Freshwater swamps consistently emit methane, with higher levels in summer and lower in cooler months. Conversely, saltwater marshes release very little, if any. This insight points to a possible mitigation strategy: increasing seawater flow into coastal swamps. Such “plumbing” adjustments could not only reduce methane but also revitalize wildlife habitats and support commercial fisheries.
As the planet warms, the bacterial processes generating methane accelerate. Moreover, increased global temperatures lead to more rainfall, potentially enlarging wetlands and, consequently, their methane output.
Concurrently, the fossil fuel industry has been working to curb its methane emissions. A recent December study indicated that methane releases from this sector have stabilized over the last twenty years.
However, Ben Riddell-Young, a lead author and research scientist at the University of Colorado Boulder, noted that during the same period, methane emissions from landfills and agricultural activities (also fueled by methane-producing bacteria) have been on the rise. He succinctly explained, “There’s more waste and more cows.”
Interactive Chart: A chart illustrates that microbes, not fossil fuels, are primarily driving methane’s rise. It displays annual methane emissions from 1999-2022. Shaded areas on the chart indicate uncertainty within one standard deviation. (Source: Proceedings of the National Academy of Sciences).
Other scientists, however, remain cautious, arguing that current measurement uncertainties make it difficult to confirm a plateau in fossil fuel methane emissions.
A recent, un-peer-reviewed analysis using data from a lost MethaneSAT satellite (developed by the Environmental Defense Fund) suggests that methane emissions from roughly half of the world’s oil and gas regions are actually 50% higher than previous EPA and European Commission estimates, which rely on ground-level fossil fuel production.
“We lack comprehensive monitoring to truly assess whether industrial and agricultural emissions are stable,” stated Ben Poulter, a senior scientist at Spark Climate Solutions.
Dr. Poulter previously led BlueFlux, a six-year NASA-funded project in the Florida Everglades that used low-flying aircraft to measure methane and carbon dioxide levels. The project faced setbacks in April following budget cuts from the Trump administration.
A recent study in the Proceedings of the National Academy of Sciences, analyzing 23 years of data from the Everglades (via satellites, aircraft, and towers), revealed that these wetlands absorbed approximately 14 million metric tons of carbon dioxide annually – roughly 10% of Florida’s yearly vehicle emissions. However, they also released six million metric tons of methane, effectively canceling out about half of the climate benefit from carbon dioxide absorption.
Dr. Poulter concurs that as the climate continues to warm, methane emissions from wetlands are worsening.
“Early on, we suspected wetlands contributed to rising methane,” he commented, “and in the last three to five years, the scientific community has largely agreed that they’re a significant factor in this acceleration.”
Video: Methane bubbles visibly escape from the swamp’s surface.
Every new discovery about methane sparks discussions on improving measurement techniques and finding effective solutions. Over 150 nations, including the United States, have committed to the Global Methane Pledge, aiming for a 30% reduction in methane emissions from 2020 levels by 2030. Achieving this could involve repairing leaks in natural gas operations, transitioning to renewable energy, modifying rice cultivation methods, and capturing methane from landfills.
However, Brian Buma, a senior climate scientist at the Natural Resources Defense Council, pointed out that this pledge overlooks natural methane sources. “When forecasting warming rates, many countries’ scenarios disregard this increasing contribution, especially from wetlands,” he stated.
On the 20-minute journey to the Louisiana marsh study site, Hunter observed bald eagles, herons, and hawks soaring above, while invasive nutria (beaver-sized rodents) moved beneath the water’s surface.
Dr. Dutta and Hunter carefully deploy a specialized dome to collect methane samples at a Luling, Louisiana research site.
A laptop screen displays real-time methane readings from the instruments.
Upon reaching the study area, Hunter stepped onto the floating marsh and carefully placed a transparent, dome-shaped plastic chamber over a cleared patch of soil. He then linked the chamber to a network of tubes and wires, connecting them to his laptop to monitor soil methane emissions for the next hour.
“While these marshes store significant carbon in their soils, we have a crucial knowledge gap regarding the fate of that carbon once buried,” Hunter noted.
Later, in a Baton Rouge chemistry lab, Hunter conducted an experiment by injecting a radioactive tracer into swamp mud sealed in a vial. This technique allows him to track methane’s journey from microbes through the soil and into the air.
“The bacteria consumed the radioactive methane, converting it into radioactive carbon dioxide,” he explained. “This radioactive carbon dioxide then serves as our indicator for how much methane they processed.”
While individual analyses are quick, gaining a comprehensive understanding of the Louisiana marsh will require months, if not years, of data collection. At just 26, Hunter is at the forefront of this research. He cautiously points out that current marshland restoration efforts in Louisiana, which involve diverting more fresh water from the Mississippi River, could inadvertently lead to increased methane emissions.
“Our goal is to thoroughly assess the environmental impact of marsh restoration, particularly concerning greenhouse gas dynamics,” Hunter affirmed.
Hunter and his colleagues emphasize that the most rapid way to mitigate the wetland methane feedback loop is to significantly cut industrial greenhouse gas emissions, including both carbon dioxide and methane, as these are the primary drivers of global warming.
Meanwhile, these scientists continue their dedicated work: identifying new methane sources in the field, collaborating with peers, and meticulously analyzing data to comprehend the shifts in Earth’s natural cycles.
“Our laboratory aims to track methane’s entire journey, from its genesis to its release into the atmosphere,” Hunter concluded. “As scientists, we are committed to doing our utmost to reduce methane emissions and, in turn, curb climate change.”