Jun 1 2016

New report calculates Alaska’s greenhouse gas potential

Plant growth in Alaska should store as much carbon as the state loses to wildfire and thawing permafrost through 2100, a new analysis predicts.

Scientists from the University of Alaska Fairbanks, U.S. Geological Survey and the U.S. Forest Service did the analysis to help understand the changing climate.

The scientists found that Alaska’s ecosystems currently capture as much carbon as they lose to the atmosphere.

However, they said, rising temperatures, more wildfires and thawing permafrost still could tip the balance and make Alaska a net carbon source. That would further increase the concentration of gases that trap the sun’s energy and warm the Earth’s atmosphere.

“The fact that Alaska isn’t projected to be a big source of carbon through 2100 is a surprise,” said co-author A. David McGuire, an ecosystem modeler with the USGS and the UAF Institute of Arctic Biology.

“The most important message is that Alaska, in general, has been a sink (reservoir) of greenhouse gases over the last 50 years,” McGuire said. “And when you look at the entire state, even considering recent decades in which the boreal region has had a lot of fire activity, Alaska is not projected to lose a lot of carbon to the atmosphere over the remainder of the century.”

Alaska has only about 18 percent of the nation’s land, but it contains more than half of the nation’s carbon.

Most of Alaska’s carbon — about 91 percent — is locked away from the atmosphere in frozen soils. Scientists are concerned about how warming temperatures, thawing permafrost, increasing wildfires and changing stream flow in Alaska will convert this carbon to greenhouse gases.

Nevertheless, the report found, plant growth in the Arctic is expected to store more carbon than is released from soils through 2100.

The ecosystems of Alaska’s uplands and wetlands already act as a moderate carbon sink, absorbing 3.7 million metric tons of carbon per year. That rate should increase in the rest of the century, as plants grow faster in warmer temperatures.

Southeast Alaska’s rainforest would also play an important role. The report estimates that the region’s productivity would increase by 8 to 27 percent under various scenarios.

Carbon released by increasing wildfire activity will partially counter the plant absorption, especially in the boreal forest blanketing the state’s central regions. Carbon is released not only when accumulated moss and other vegetation burns but also if the underlying frozen peat exposed by fires thaws in the summer.

With projected increases in temperature, wildfires and permafrost thawing, carbon releases beyond 2100 may be larger than those before 2100, the scientists said.

“The models for permafrost thaw between 2100 and 2200 tend to show a great loss of carbon, and that may be the case for Alaska,” said McGuire.

The distribution of plants in Alaska also is changing and will continue to change.

“The report shows that there will be quite a substantial shift from coniferous forest to deciduous forest,” said co-author Scott Rupp, forest ecologist and director of the UAF Scenarios Network for Alaska and Arctic Planning. “And the tundra will continue to shift from grass to shrub.”

Historically, national assessments of carbon stock and greenhouse gas levels have not included Alaska because of its size, lack of roads and meager field data.

This state-based investigation is the most recent chapter of a nationwide study that Congress mandated in 2007 under the Energy Independence and Security Act.

“We’re still learning a lot in this field,” said Virginia Burkett, USGS associate director for climate and land use change. “While we can’t yet portray these types of studies as precise or definitive, it is absolutely vital that we pursue a field-based understanding of the carbon cycle of the Earth in various settings so we can better understand both the natural and the human-influenced mechanisms of climate change. This assessment was based on the best available data from field surveys, remote sensing, authoritative maps and model simulations.”

ON THE WEB: The USGS publication, Baseline and Projected Future Carbon Storage and Greenhouse-Gas Fluxes in Ecosystems of Alaska, is available online. McGuire and USGS colleague Zhilang Zhu were co-lead authors of the report.

The lead authors have prepared an auxiliary set of slides: http://bit.ly/USGS-Carbon-2016 that highlight key findings and statistics of the assessment.

ADDITIONAL CONTACTS: David McGuire, 907-474-6242, admcguire [at] alaska [dot] edu & Scott Rupp, 907-474-7535, tsrupp [at] alaska [dot] edu

MEDIA CONTACTS: Marie Thoms (for McGuire) 907-474-7412; Kristin Timm (for Rupp) 907-474-7064