A recent study published in the journal Nature Climate Change has found that rising temperatures and increased precipitation are the main factors responsible for the increase in methane emissions from wetlands. Wetlands are areas where water covers the soil either seasonally or permanently.
According to the study, methane emissions from wetlands have been increasing at a rate of 1.3-1.4 teragrams per year between 2000 and 2021.
The study also revealed that methane emissions in 2020 and 2021 have increased significantly by 14-26 teragrams per year and 13-23 teragrams per year, respectively, compared to the period between 2000 and 2006.
A new study has revealed that wetlands such as swamps, marshes, permafrost, bogs and fens are responsible for one-third of the total methane emissions, a potent greenhouse gas that has contributed to around 30% of the temperature rise since pre-industrial times.
On a 20-year timescale, methane is 84 times more potent than carbon dioxide. Wetlands are known to store more than 33% of the world’s terrestrial carbon.
However, they also release approximately 127-155 Tg of carbon each year, largely due to microbes. In 2020 and 2021, methane emissions from wetlands reached unprecedented levels.
The research, carried out by scientists from France, China, and the United States, focused on the impact of climate change on wetland methane emissions from 2000 to 2021.
The wetland methane feedback
Methane is a potent greenhouse gas that has contributed to approximately 30% of human-caused global warming since the Industrial Revolution.
The primary sources of methane emissions are human activities such as fossil fuel production, agriculture, and landfill sites. In 2021, several countries, including the US, EU, Indonesia, Canada, Brazil, and the UK, pledged to cut their methane emissions by 30% over the next decade.
A recent report by the International Energy Agency’s global methane tracker identified energy operations in the oil and gas sector as the most cost-effective area for methane abatement. However, natural sources account for 40% of methane emissions, with wetlands being the largest contributor.
Wetlands, which take various forms and support 40% of all species, are vital for ecosystem services such as water filtration and carbon storage. Wetland restoration is considered a crucial climate mitigation strategy, but wetlands can also release greenhouse gases.
Wetland methane emissions rising faster than expected
A new study has found that wetland methane emissions have risen at a faster rate than projected under the most pessimistic emission scenario (RCP8.5).
Over the past 20 years, wetland methane emissions have risen by 1.2-1.4m tonnes per year, compared to projected growth of 0.9m tonnes of methane per year under RCP8.5.
The study, which analysed wetland methane emissions from 2000-2021, also found an “exceptional” increase in methane emissions over 2020-21.
Global average annual emissions increased by 8-10m tonnes per year over 2007-21 due to climate change, compared to a 2000-06 baseline. However, emissions grew by 14-26m tonnes in 2020 and 13-23m tonnes in 2021.
The findings support recent research suggesting that methane emissions associated with wetlands are increasing rapidly due to positive climate feedbacks.
Wetlands as sources and sinks of greenhouse gases
A separate study published in Nature Climate Change investigates how global warming will impact greenhouse gas emissions from wetlands.
The study uses observations from 167 sites to assess the emissions of methane, carbon dioxide and nitrous oxide. While wetlands are currently a sink of greenhouse gases, the study finds that the “100-year global warming potential of wetlands” could rise by 57% under a global temperature increase of 1.5-2C.
The authors also found that greenhouse gas emissions from wetlands depend on the type of plant found in the wetland.
The study warns that “warming undermines the mitigation potential of pristine wetlands”, adding that there is “major uncertainty” over whether or not wetlands will remain a carbon sink as the planet warms.
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