Permafrost thaw spurs methane emissions

Arctic soil that’s been frozen for thousands of years is thawing at an alarming rate due to climate change. Melting permafrost frees up water and nutrients that could spur the growth of methane-producing bacteria and methane-transporting plants. Scientific modeling suggests this could cause a disastrous positive-feedback loop, whereby increased methane emissions cause further warming, which thaws more permafrost, leading to more methane emissions, and so on. Now researchers report experimental evidence for the connection between nutrients released from permafrost thaw and increased methane emissions. Mark Lara, a plant biologist at the University of Illinois at Urbana-Champaign, and his team traveled to a research site outside Utqiaġvik, Alaska, where the tundra is increasingly populated by the methane-transporting grass Arctophila fulva. This plant acts like a straw, rapidly transporting the gas out of the soil and into the air, Lara says. The team took tundra samples back to the lab and exposed them to high levels of nitrogen and phosphorus consistent with those released during permafrost thaw. Methane emissions increased by 64% in these samples, compared with those given lower levels of these nutrients (J. Geophys. Res. Biogeosci. 2019, DOI: 10.1029/2018JG004641). Lara says he doesn’t know whether these results apply to other regions, as Arctic plant and bacteria populations vary.