Global Warming Could Make Microbes Living in Alaskan Tundra Release More Greenhouse Gases, Scientists Warn

Scientists who studied the Alaskan tundra have warned that global warming could make microbes which live in the soil release more greenhouse gases. The permafrost soils on the northern latitude make up around 16 percent of the Earth's surface, but harbor about half of our planet's total carbon beneath its surface. As such, disruptions to this area have the potential to worsen climate change, the authors of the study published in the journal PNAS explained.

To find out what might happen to the microbes if the frigid soil is heated up by rising global temperatures, the team visited a "moist, acidic tundra area" at a site in interior Alaska, near Denali National Park in the Eight Mile Lake region. Past research has shown the northern latitude has experienced rates of warming above the global average, and the permafrost in the area chosen by the team has thawed in the past few decades.

Researchers marked six experimental blocks around 100 meters from one another in September 2008, and in the winter put up two snow fences around each plot. The fences blocked strong winds, and the thicker snow which landed on the experimental blocks as a result of the fences raised the temperature by around 1.1 degrees Celsius (2 degree Fahrenheit) compared with the control plots.

Scientists removed cores of soil from the experimental and control blocks 1.5 years after the start of the experiment, and then after 4.5 years, from depths of 15 to 25 centimeters and 45 to 55 centimeters. The former represents soil which is frozen during the winter but thaws in the warmer months between May to September, while the latter relates to the permafrost which thaws only for a brief period every year.

Next, the team sequenced the DNA of the microbes living in the soil, and compared the results of the control and experimental plots.

Eric R. Johnston, a postdoctoral researcher at Oak Ridge National Laboratory who worked on the study while completing his PhD at Georgia Tech, commented in a statement: "At the upper boundary of the initial permafrost boundary layer—45 to 55 centimeters below the surface—the relative abundance of genes involved in methane production (methanogenesis) increased with warming, while genes involved in organic carbon respiration—the release of carbon dioxide—became more abundant at shallower depths."

More widely, existing research has similarly shown methane and carbon dioxide are being released at a greater rate throughout the region in recent years "as a result of climate warming," said Johnston.

Kostas T. Konstantinidis, co-author of the study and a professor at the Georgia Institute of Technology, commented in a statement: "We saw that microbial communities respond quite rapidly—within four or five years—to even modest levels of warming."

Konstantinidis explained: "Because of the very large amount of carbon in these systems, as well as the rapid and clear response to warming found in this experiment and other studies, it is becoming increasingly clear that soil microbes—particularly those in the northern latitudes—and their activities need to be represented in climate models," he said. "Our work provides markers—species and genes—that can be used in this direction."

Their conclusion mirrored the sentiment of a consensus statement published by scientists last week, which stressed humanity can't afford to forget the part microbes play in climate change.

Some 33 scientists across fields including environmental microbiology and microbial ecology from thirty-five research institutions in eight countries published the "warning to humanity" in the journal Nature Reviews Microbiology.

Jae-Llane Ditchburn, lecturer in molecular biology at the University of Cumbria who was not involved in the PNAS study, told Newsweek: "This study is significant because it brings a compelling microbial perspective into thawing permafrost in climate change.

"While previous studies have investigated laboratory-incubated permafrost soils under controlled conditions, this study has gone further to execute a longitudinal experiment in the field," she said.

Referring to the United Nations' Intergovernmental Panel on Climate Change, she said: "The IPCC hasn't yet accounted for soil microbial communities particularly in thawing permafrost (as per their 2018 special report of global warming of 1.5C) so their findings add information to be considered for future climate change modeling."

Professor Lars Bakken, an expert in microbial physiology and ecology at the Norwegian University of Life Sciences, who didn't work on the paper, told Newsweek: "I was surprised that such modest changes in temperature could induce such profound changes of the microbiota or the soils.

"Although the study enriches our understanding of how climate change affects microbial life in tundra soils, the information is unlikely to improve our predictions of the systems' climate forcing."

This article has been updated with comment from Lars Bakken.