The world’s warming tropical wetlands are emitting more methane than ever before, signalling a troubling acceleration in climate change that could further derail global climate goals.

Recent research highlights a significant and largely unaccounted surge in methane emissions, primarily from tropical wetlands, that may compel governments to intensify cuts in emissions from fossil fuel and agricultural sources.

Wetlands store immense amounts of carbon in decaying plant matter, which is broken down by microbes in oxygen-poor conditions. As global temperatures rise, this process accelerates, increasing methane production. Heavy rainfall and flooding, driven by shifting climate patterns, have further expanded wetland areas, compounding the issue.

Although scientists have long anticipated rising methane emissions from wetlands in a warming climate, atmospheric measurements from 2020 to 2022 revealed methane concentrations at their highest levels since systematic recording began in the 1980s.

Four recent studies point to tropical wetlands as the main source of this unprecedented increase, with these regions contributing over 7 million tonnes to the methane spike in recent years.

“Methane concentrations are not just rising, but rising faster in the last five years than any time in the instrument record,” said Stanford University environmental scientist Rob Jackson, who chairs the group that publishes the five-year Global Methane Budge, last released in September.

Advanced satellite instruments pinpointed the tropics as the epicentre of the surge. Further analysis of methane’s chemical signatures confirmed its natural origin, linked to wetlands rather than fossil fuels. The Congo Basin, Southeast Asia, the Amazon, and southern Brazil emerged as significant contributors.

Data published in Nature Climate Change in March 2023 show that wetland emissions have exceeded previous worst-case climate projections by about 500,000 tonnes annually over the past two decades. This suggests that existing climate models may underestimate methane’s role in global warming.

“We should probably be a bit more worried than we are,” said climate scientist Drew Shindell at Duke University.

The La Niña climate pattern, which causes heavier rainfall in parts of the tropics, was partially responsible for the recent emissions surge, according to a September study in Proceedings of the National Academy of Sciences. However, La Niña alone cannot account for the record-high methane levels, indicating broader climatic and ecological factors are at play.

Methane is 80 times more potent than carbon dioxide in trapping heat over 20 years and has contributed to about one-third of the 1.3°C (2.3°F) warming since 1850. While methane dissipates from the atmosphere within a decade, its short-term impact on warming is profound.

To meet the Paris Agreement’s goal of limiting global warming to 1.5°C (2.7°F), governments must address rising wetland methane emissions. Over 150 nations have pledged to cut methane emissions by 30% from 2020 levels by 2030, focusing on reducing leaks from oil and gas infrastructure. However, progress has been slow.

According to the International Energy Agency’s 2024 Global Methane Tracker, fossil fuel methane emissions have remained at record highs, around 120 million tonnes annually, since 2019.

Satellite observations have identified over 1,000 significant methane leaks from oil and gas operations in the past two years. However, only 12 leaks were addressed by the countries notified, according to a U.N. Environment Programme report.

Some nations have outlined ambitious plans to combat methane emissions. For instance, China has pledged to reduce flaring at oil and gas wells. Meanwhile, the Democratic Republic of Congo, the largest tropical methane emitter in 2024, is working to monitor and manage methane from its extensive swampy forests and wetlands, according to Environment Minister Eve Bazaiba.

“We don’t know how much [methane is coming off our wetlands],” she said. “That’s why we bring in those who can invest in this way, also to do the monitoring to do the inventory, how much we have, how we can also exploit them.”

As methane emissions from tropical wetlands continue to rise, scientists warn that global climate goals will become increasingly unattainable without stronger action.

 

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