Beavers are moving further into the tundra as the Arctic warms with their construction activities causing a higher release of the greenhouse gas methane.
In many places, nature lovers rejoice at the beavers’ remodeling efforts as they enrich ecosystems and increase species richness. However, in the Arctic tundra, where the American beaver (Castor canadensis) has been expanding over the past 50 years due to rapid Arctic warming, its activities are causing problems that could exacerbate climate change.
They build dams, often flooding the surrounding vegetation and turning arctic rivers and streams into lentic water. Flooding leads to faster thawing of permafrost, which promotes the release of the greenhouse gases carbon dioxide and methane. In addition, beaver dams impede or even prevent the onward transport of organic material, which is subsequently deposited in beaver ponds. The accumulated organic material is degraded by oxygen-consuming microorganisms, creating ideal conditions for the release of methane.
In a recent study, a research team led by the University of Alaska Fairbanks used satellite data and airborne remote sensing to examine, for the first time at the landscape level, whether more methane is released into the atmosphere around beaver ponds.
The study area, located in northwest Alaska in the lower Noatak River basin, covers an area of 430 square kilometers, where the researchers identified methane hotspots using hyperspectral cameras. In the journal Environmental Research Letters, the team reports that there are many methane hotspots near the ponds which become smaller with increasing distance from the pond. They came to this conclusion by comparing the location of methane hotspots with the location of 118 beaver ponds and non-beaver streams and lakes as determined from satellite imagery. There are 51 percent more methane hotspots near beaver ponds than around waterbodies with no beaver activity, according to the study.
In the study, the researchers report that beaver activity in the region was minimal until 2000 but has increased sharply in recent times. In particular, damming drained thermokarst lakes would lead to greater methane release, as they are rich in organic matter and are likely to promote methanogenesis to a significant degree, the authors said.
The research team expects that beaver activity in the Arctic will increase the release of methane, at least initially. “We say ‘initially’ because that’s the data we have,” Ken Tape, research professor at the University of Alaska Fairbanks Geophysical Institute, said in a university news release. “What the longer-term implications are, we don’t know.”
Methane is a greenhouse gas 25 times more potent than carbon dioxide and contributes significantly to atmospheric warming. According to the U.S. Environmental Protection Agency, methane concentrations in the atmosphere have more than doubled over the past 200 years due to human activities.
Julia Hager, PolarJournal
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