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African Wetlands a Major Source of Methane Emissions, Study Finds

Climate
The largest wetland in Africa is in the South Sudan. George Steinmetz / Corbis Documentary / Getty Images Plus

Methane emissions are a far more powerful greenhouse gas than carbon dioxide – about 28 times more powerful. And they have been rising steadily since 2007. Now, a new study has pinpointed the African tropics as a hot spot responsible for one-third of the global methane surge, as Newsweek reported.


Satellite data captured a large influx of water from East African lakes, including Lake Victoria, flowing into the wetlands of South Sudan. That water triggered plant growth and microbial activity that produced a massive amount methane, as the BBC reported.

"Methane is the second most important greenhouse gas, behind carbon dioxide," Mark Lunt, an atmospheric scientist at the University of Edinburgh in Scotland, told Newsweek. "We need to be able to understand how and why it is changing in our atmosphere to inform how we might mitigate future emissions."

Lunt is the lead author of the new study published in the journal Atmospheric Chemistry and Physics. Lunt and his team used six years of satellite imagery to figure out if there was methane coming from Africa, which had been largely overlooked because of a dearth of atmospheric data, according to Newsweek.

"There are very few studies that have focused in detail on Africa, primarily because there isn't much atmospheric methane data from there," said Lunt in a university press release. "Using satellite data gives a unique perspective on the continent that wouldn't otherwise be available."

The research team used data from GOSAT, the Japanese Greenhouse Gases Observing Satellite, to look at annual and seasonal methane emissions in sub-Saharan Africa.

The area identified in the study, the South Sudanese wetland, is recognized by UNESCO as one of the largest freshwater ecosystems in the world. It covers an estimated 22,000 square miles.

Satellite images "show the Sudd wetlands expanded in size, and you can even see it in aerial imagery – they became greener," said Paul Palmer, an atmospheric scientist at the University of Edinburgh who co-authored the research, to the BBC. "There's not much ground-monitoring in this region that can prove or disprove our results, but the data we have fits together beautifully."

The new research helps put together the pieces of a puzzle that has vexed scientists about the sources of methane emissions. While fossil fuels and agricultural practices have certainly made enormous contributions to the release of methane, there is undoubtedly a natural source as well, as the BBC reported.

Methane in the atmosphere had stabilized during the early 2000s, but atmospheric concentrations spiked in 2007 and then again in 2014.

"Global levels of methane in the atmosphere have been on the rise since the mid-2000s, after a period of relative stability," said Lunt, as Newsweek reported. "There are many different explanations for why this is the case but the primary suspects have been an increase in microbial sources such as wetlands and agriculture from the tropics, as well as increases in fossil fuel emissions from countries such as the U.S. and China. Alternatively the sink – the process of removal of methane in the atmosphere – could have decreased resulting in the resumption of growth we see."

The climate crisis will lead to an increase in methane emissions from natural sources, since warmer temperatures will cause wetland microbes to accelerate the rate they break down and to release more methane, according to a study published in the Proceedings of the National Academy of Sciences.

"Wetland methane is produced through a process known as methanogenesis. Essentially wetlands are anaerobic environments which are ideal for the production of methane," Lunt explained Newsweek. "Microorganisms break down organic matter in a process that results in the production of methane."

Lunt added that a study like this is important for identifying future interventions and improving predictions for Earth's climate.

"In order to understand how methane might change in the future, it is essential that we can adequately explain changes in the present and recent past," said Lunt in a University of Edinburgh statement. "Studies such as this can help narrow down the list of possible explanations, and hopefully improve our predictive capabilities for the future."

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