New research, published in the journal Nature Communications, suggests that methane emissions from lakes in the northern hemisphere could double in the next 50 years, due to a “feedback loop,” according to BBC News. As the climate warms, more cattail plants are growing in the areas around freshwater lakes. When pieces of these plants fall into the lake, it greatly boosts the amount methane that is produced – and methane is 25 times as potent as a greenhouse gas as carbon dioxide.
Currently, freshwater lakes emit 16 percent of the world’s natural methane emissions, compared to the 1 percent from all of the world’s oceans combined.
Methane is released when microbes in sediment on the lake floor consume organic material, such as pieces of plants, that sink to the bottom of the lakes. According to the new research, the amount of methane emissions vary greatly depending on what materials fall into the lake. The study compared emissions from cattails to those from coniferous and deciduous trees. In a 150-day incubation period, the cattails yielded 400 times the amount of methane emitted from conifer tree material. According to researchers, deciduous and coniferous trees may contain chemicals that limit the amount of methane produced by the microbes.
The paper’s senior author, Dr. Andrew Tanentzap of the University of Cambridge, said to BBC News:
“The cattails don’t have the same chemicals and so they are no longer inhibiting the microbes from producing methane…by now comparing what’s happening in the reed beds to what’s might happening beneath a forest – wow, it’s a massive difference!”
The study warns that this mechanism could lead to substantially more greenhouse gases being emitted from freshwater lakes, and since a warming climate can lead to increased growth of aquatic plants, this phenomenon could create a feedback loop of higher and higher levels of methane.
The researchers found that the number of lakes in the northern hemisphere surrounded by cattails could double between 2041 and 2070, leading to an methane output to rise 73 percent during the growing season.
“This forecasts a whole range of these different aquatic plants moving northwards with warmer temperatures into a part of the world that’s dominated with lakes so there is going to be more habitat available to them,” according to Tanentzap.
Other researchers praised the study as an important revelation about what to expect from the coming decades of climate change. According to York University’s Sapna Sharma, an expert in how climate change will impact lakes:
“This study was able to elucidate a mechanism by which lakes may produce even more methane that previously thought. Uncovering another potential source of methane production from boreal lakes is useful to further understanding global carbon cycles and ultimately improve climate projections.”