Natural methane emissions rise in warmer temperatures

The results of a decade-long investigation suggest that methane emissions from natural resources will be higher than predicted. According to the study, global warming is shifting the balance of the microbial communities that regulate methane within ecosystems.

Two types of microorganisms are responsible for the production and removal of methane. Methanogens naturally produce methane, while methanotrophs convert it into carbon dioxide. 

Past studies have found evidence that these processes will respond to global warming differently. 

For the current study, researchers conducted experiments in artificial ponds for 11 years to examine how freshwater microbial communities respond to rising temperatures.

The team found that global warming increased methane production, but not methane removal. The disproportionate effects led to higher methane emissions that have not been identified in previous studies that focused on temperatures alone.

Study co-author Mark Trimmer is a professor of Biogeochemistry at Queen Mary University of London.

“Our observations show that the increase in methane emissions we see is beyond what you could predict based on a simple physiological response to the temperature increase,” said Professor Trimmer. 

“Long-term warming also changes the balance in the methane-related microbial community within freshwater ecosystems so they produce more methane while proportionately less is oxidized to carbon dioxide.” 

“As methane is a far more potent greenhouse gas than carbon dioxide, together these effects increase the global warming potential of the carbon gases released from these ecosystems.”

The research team also conducted a meta-analysis of published data on methane emissions from wetlands, forests, and grasslands worldwide. The analysis confirmed that ecosystems produce a disproportionate amount of methane in response to warming, resulting in a higher rate of emissions.

“Our findings fit with what we see in the real world for a wider variety of ecosystems,” said Professor Trimmer. “Together these results suggest that as Earth temperatures increase through global warming, natural ecosystems will continually release more methane into the atmosphere.”

Over a 100-year period, methane has about 28 times the global warming potential of carbon dioxide. At least 40 percent of methane is released from freshwaters such as wetlands, lakes, and rivers.

Study co-author Dr. Kevin Purdy is an associate professor of Microbial Ecology at the University of Warwick. 

“Our studies have led to a better understanding of how global warming can affect methane emissions from freshwaters,” said Dr. Purdy. “This means that future predictions of methane emissions need to take into account how ecosystems and their resident microbial communities will change as the planet warms.”

The study is published in the journal Nature Climate Change.

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By Chrissy Sexton, Earth.com Staff Writer