Climate change could reduce Amazon's methane absorption by 70%: Study

Extreme temperatures and humidity driven by climate change could reduce the Amazon rainforest's capacity to absorb the greenhouse gas methane by 70 per cent, a study has found.

Researchers said that under a warmer climate, the extreme rainfall and droughts projected for South America's Amazon could impact its net greenhouse gas emissions.

Often referred to as the 'lungs of the planet', the tropical rainforest lies majorly in Brazil, with parts in Peru, Colombia, Ecuador, among others, and is known to be a crucial 'greenhouse gas sink' that absorbs these gases from the air.

However, 20 per cent of the Amazon region, which remains flooded for nearly half a year, releases methane, countering its ability to absorb other greenhouse gases, the researchers at the University of Sao Paulo, Brazil said. Their study is published in the journal Environmental Microbiome.

Previous studies have shown that the flooded areas of Amazon contribute up to almost 30 per cent of methane emissions from wetlands globally.

"Although it's already been shown that factors such as air temperature and seasonal flooding can influence the composition of microbial communities affecting the flow of methane in these environments. But what should we expect in the context of climate change and the projected extreme weather?" Lead author Julia Gontijo, a postdoctoral researcher at the University of California, Davis, US, said.

For this study, researchers took soil samples from two flooded regions of the Amazon and one from elevated forests known to absorb methane. These samples were subjected to extreme temperatures -- 27 degrees Celsius and 30 degrees Celsius -- and humidity.

They found that in the soil sample from the elevated forest methane absorbtion dropped by 70 per cent in hot and dry conditions, while methane production surged in heavy rainfall, as the soil was not used to dealing with extreme humidity.

"Within this (elevated) forest soil, an average decrease of 70 per cent in (methane) consumption potential was observed with temperature increase in dry conditions," the authors wrote.

It means that the floodplain microbiome can adapt to climate change but the upland forest microbiome is sensitive to its effects, which could cause a shift in the balance of greenhouse gas emissions in the Amazon in future, Gontijo said.

"In view of the Amazon Rainforest biome's importance in proportion to global levels, this could represent a very serious problem," she said.

She further said that in both (the) floodplains, although there were no observation of significant changes in methane emission patterns, the number of methane-producing microorganisms increased that can be a future problem.

The results could be used in framing public policies, the author added.