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Climate: Permafrost thaw doubles carbon losses

Study says greening tundra won’t offset permafrost meltdown

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Study says new plant growth won’t compensate for carbon emissions from melting tundra in the Arctic. bberwyn photo.

Staff Report

FRISCO — Permafrost could dwindle by 30 to 70 percent by the end of the century, and more vegetation in the Arctic won’t be enough to offset the carbon emissions from thawing organic soils.

Scientists with the Woods Hole Research Center reached their conclusions after a series of field tests designed to measure net gains or losses in carbon emissions. The study is published in the journal Ecology.

“Our results show that while permafrost degradation increased carbon uptake during the growing season, in line with decadal trends of ‘greening’ tundra, warming and permafrost thaw also enhanced winter respiration, which doubled annual carbon losses,” said WHRC assistant scientist Sue Natali.

Permafrost contains three to seven times the amount of carbon sequestered in tropical forests. A warming climate is already thaw permafrost, which will result in the release of carbon dioxide and methane into the atmosphere creating feedbacks to climate change — more warming and greater permafrost thaw.

Prior to this study, “the understanding of permafrost feedbacks to climate change had been limited by a lack of data examining warming effects on both vegetation and permafrost carbon simultaneously,”  Natali said.

“There is 100 times more carbon stored below ground than above ground in the Arctic, so observed changes in plant productivity are only a very small component of the story. Given the amount of carbon stored below ground in the arctic, it is very unlikely that plant growth can ever fully offset losses from permafrost thaw,” Natali said.

The three year Carbon in Permafrost Experimental Heating Research project warmed air and soil and thawed permafrost using two warming experiments. The “winter warming” treatment consisted of snow packs, which functioned like down comforters insulating the ground during the winter until the snow was removed at the start of the growing season. The “summer warming” treatment consisted of open-topped greenhouses that warmed the air during the summer. The team measured warming effects on CO2 uptake by plants and release by plants and microbes.

“The only way we can accurately project future climate is to understand the responses of both plants and microbes to a warming climate,” Natali said. “This study was the first to simulate whole ecosystem warming in the arctic, including permafrost degradation, similar to what is projected to happen as a result of climate change. There is a strong potential for significant global carbon emissions if rates calculated here become typical for permafrost ecosystems in a warmer world.”

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