Methane emissions from wetlands rose 5-6% since 2000-2006: Study

Methane is responsible for roughly 30 per cent of the rise in temperature since the pre-industrial period

By Rohini Krishnamurthy
Published: Wednesday 22 March 2023
Photo: iStock12jav.net

Warming temperature and increased precipitation appears to be driving methane emissions from wetlands – land areas where water covers the soil either seasonally or permanently, according to a new study.

Methane emissions from wetlands rose at a rate of 1.3-1.4 teragrams (1 Tg equals 1,000,000 tonnes) per year from 2000 to 2021, the study published in Nature Climate Change journal highlighted.

Emissions in 2020 and 2021 increased by 14-26 Tg per year and 13-23 Tg per year, respectively, compared to 2000-2006. 

Methane is responsible for roughly 30 per cent of the rise in temperature since the pre-industrial period. It is also 84 times more potent on a 20-year timescale.

Wetlands like swamps, marshes, permafrost (permanently frozen ground), bog and fens are responsible for a third of total methane emissions.

Fens are wetlands fed by groundwater, while bogs are depressions filled by rainwater.

Wetlands store more than a third of the world’s terrestrial carbon. However, they can also act as a source, releasing roughly 127-155 Tg of carbon annually, a 2021 study stated. This is largely attributed to microbes inhabiting wetlands.

Moreover, methane emissions reached record levels in 2020 and 2021. Evidence suggests that living sources had a role in it.

Researchers from China, the United States and France investigated climate-change-driven wetland methane emissions from 2000 to 2021.

They simulated methane emissions based on data from ground-based meteorological stations.

The other source of data was from reanalysis, which is observations with past short-range weather forecasts rerun with modern weather forecasting models. 

Their analysis showed that global mean annual methane emissions in 2007–2021 due to climate change impacts on wetlands increased by 8–10 Tg per year compared to 2000–2006. This represents a 5–6 per cent jump.

Wetlands from South America were the single largest contributor, according to simulations from ground-based stations.

Reanalysis-based simulations indicated that Africa, South Asia and Southeast Asia are also responsible for high emissions from wetlands. 

Wetlands in the tropics contributed the most to the spike in 2020 and 2021. “Tropical wetlands are emerging hotspots, with 2020 and 2021 being highly anomalous years,” the researchers wrote in their study. 

Methane emissions cause a positive climate feedback, which means it amplifies warming. Increased rain due to global warming, for instance, creates more wetlands, which increase methane emissions. This, in turn, causes more global warming and rain, creating a feedback loop.

Despite this, most climate models such as Earth System Models and Integrated Assessment Models that were a part of the last Assessment Report of the Intergovernmental Panel on Climate Change do not consider this process. 

The models focus on the long-term increase in atmospheric methane concentrations due to human activities such as industry and agriculture, the study highlighted.

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