Zürcher Nachrichten - Arctic warming spurs growth of carbon-soaking peatlands

Peatlands are the largest terrestrial store of carbon, locking away twice as much heat-trapping CO2 from the atmosphere in their waterlogged soils as all the world's forests.

These carbon-rich reservoirs, composed of partially decayed organic matter, only cover three percent of Earth's surface, and generally fade out in the far north where harsh weather limits plant growth.

But warmer temperatures caused by climate change have improved growing conditions for plants in the Arctic, and satellite data has shown a general "greening" of this frosty region.

Using drones, satellite imagery and on-the-ground observations, an international team of scientists assessed peatlands in the European and Canadian Arctic to see if they had benefited from warmer climes.

They found strong evidence that peatlands "have likely undergone lateral expansion over the last 40 years" in the Arctic, which is the fastest warming region on Earth.

"The permafrost thaws a little, provides a water source for vegetation, and surface vegetation recovers. In this study, we specifically see a lateral expansion," Michelle Garneau, a professor at the University of Quebec in Montreal, and co-author of the study, told AFP.

The most marked change was observed where summer temperatures have risen the most, such as in the Norwegian archipelago of Svalbard.

"All these new vegetated surfaces that didn't exist three decades ago are currently actively absorbing carbon," Garneau added.

This suggests Arctic peatlands "are an increasingly important natural carbon sink, at least in the near term", said study co-author Karen Anderson, a professor from the University of Exeter, which led the research.

But how they respond to climate change in future is "still highly uncertain", said the study published in the peer-reviewed journal Communications Earth and Environment.

Recent modelling suggests that northern peatlands "may become a carbon source from mid-century" as they dry out and permafrost thaws, the study said.

They are also at risk from wildfires, which release masses of stored up carbon at once.

"If temperatures continue to rise, we are likely to see changes in rainfall, and we are not sure how sustainable new or existing peatlands will be," said Anderson.

More peatlands also means more natural emissions of methane, a potent greenhouse gas far more effective at trapping heat than CO2.

"So while our study gives us some positive news, it does not detract from the urgent need to reduce greenhouse gas emissions and stabilise our climate," said Anderson.

S.Scheidegger--NZN