Canadian Lakes Could Emit 73% More Methane as Atmosphere Warms
This story has been corrected to remove an inaccurate reference to the number of lakes in the world, based on an inaccurate reading of the source material for the story. Check the comments section below for details.
Freshwater lakes in Canada and around the world could become a potent new source of methane and atmospheric vapour as they respond to a warming climate, according to two recent studies.
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Methane releases from Canada’s northern lakes could increase 73% as climate change shifts the way vegetation decays, a team of British, Canadian, and German scientists report in the journal Nature Communications. And faster evaporation of the world’s lakes could release more of the “most abundant greenhouse gas of them all,” Climate News Network reports, releasing 16% more water into the atmosphere as vapour by 2100, according to U.S. and Chinese researchers publishing in Nature Geoscience.
The study of Canadian lakes “took samples from the decaying vegetation—deciduous leaves, pine needles and reeds and rushes—in lake beds and incubated them for 150 days to see what gases emerged,” Climate News Net states. “Those lakes rich in cattails—sometimes called bulrushes—produced 400 times more methane than lakes layered with conifer needles, and 2,800 times the methane from deciduous leaves submerged in temperate forest lakes.”
The study found that the number of lakes in the Canadian Shield colonized with a type of cattail could double in the next 50 years, producing 73% more methane. “We believe we have discovered a new mechanism that has the potential to cause increasingly more greenhouse gases to be produced by freshwater lakes,” said University of Cambridge researcher Andrew Tanentzap. “The warming climates that promote the growth of aquatic plants have the potential to trigger a damaging feedback loop in natural ecosystems.”
The evaporation study, meanwhile, found that the 80% of the world’s lakes located in high latitudes will freeze later in winter and thaw earlier in spring as the atmosphere warms. “That would mean more open water, which absorbs [solar] radiation more efficiently than ice,” Climate News Net notes.
“At the same time, warmer temperatures would deliver more energy to support evaporation: the two processes could account for half of all future changes in evaporation. So much energy is trafficked in the process of lake evaporation that researchers have even suggested it as a potential source of renewable electricity.”
“Typically, we focus on the ‘top-down’ ways that the upper part of the atmosphere triggers feedbacks that enhance warming,” said Yale University meteorologist Xuhui Lee. “But if we want to make accurate predictions of hydrological changes, we’ll need to understand what’s happening at the bottom of the atmosphere, including what’s happening at the surface of lakes—because those changes are driving the hydrological response to climate change.”