Swamp helped spark rise in climate-warming gas

Methane emissions from a vast swamp in East Africa played a key role in a recent rise in levels of the gas in the atmosphere, a study suggests.

Satellite data have revealed that East Africa accounted for a third of the increase in global levels of methane between 2010 and 2016.

The rise of 1.5 million tonnes each year is roughly the same as the amount emitted annually by the UK, researchers say.

Natural source

Much of the gas – which is around 25 times more potent at trapping heat than carbon dioxide – was produced by microscopic bacteria in a vast swamp in South Sudan called the Sudd wetlands, the team say.

Their findings improve understanding of natural sources of methane and could aid the development of more accurate models to predict emission levels.

Methane levels

A lack of data had until now meant it was difficult for scientists to assess Africa’s contribution to global levels of methane, which is also emitted by other sources including livestock and burning of fossils fuels.

Atmospheric levels of the greenhouse gas – which is second only to carbon dioxide in terms of its contribution to climate change – have risen steadily since 2007, but the cause is poorly understood.

Satellite data

A team led by Edinburgh scientists used satellite data to analyse methane emissions from Africa between 2010 and 2016.

They found that around 90 per cent of the 1.5 million tonne rise in emissions each year came from East Africa alone.

This is likely because the Sudd wetlands – which cover an area roughly twice the size of Wales – had at the time been extended as a result of increased water levels in upstream rivers, researchers say.

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. Studies such as this can help narrow down the list of possible explanations, and hopefully improve our predictive capabilities for the future.

Dr Mark LuntSchool of GeoSciences

The study, published in the journal Atmospheric Chemistry and Physics, was funded by the Natural Environment Research Council. The work also involved researchers from the National Centre for Earth Observation, the Centre for Ecology and Hydrology and the University of Leicester.

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