Peatlands across the Arctic are expanding as the climate warms, new research shows.
Scientists used satellite data, drones and on-the-ground observations to assess the edges of existing peatlands (waterlogged ecosystems that store vast amounts of carbon).
The study – led by the University of Exeter – found peatlands in the European and Canadian Arctic have expanded outwards in the last 40 years.
While this could slow climate change by storing carbon, the researchers warn that extreme future warming could cause widespread loss of peatlands – releasing that carbon and further accelerating the climate crisis.
"The Arctic has warmed faster than the rest of the planet, with average temperatures increasing by about 4°C in the last four decades," said Dr Katherine Crichton.
"This has improved growing conditions for plants, causing 'greening' of the Arctic. We wanted to identify if this greening could be from peatland plant communities.
"We know from paleo records that warmer periods in Earth's history led to more carbon being stored in peatlands.
"Our new study puts these pieces together to examine whether our warming climate is causing peatland expansion – and we find strong evidence that it is."
Peatlands cover just 3% of Earth's surface but they store about 600 billion tons of carbon – more than all the world's forest biomass combined.
The Arctic has large peatland areas but these peter out in the far north, where harsh conditions limit plant growth.
In the new study, researchers examined 16 sites – a range of peatlands in both the low and high Arctic – and compared data from 1985-95 with the last 15-20 years.
They found strong evidence of expansion at more than two thirds of sites (measured by "peak-summer greening" – increased growth of peatland-forming plants at the edges of existing peatlands).
The largest changes were found in places with the highest increases in summer temperature, such as the Norwegian islands of Svalbard.
"Our findings suggest Arctic peatlands are an increasingly important natural carbon sink, at least in the near term," said Professor Karen Anderson, from the Environment and Sustainability Institute on Exeter's Penryn Campus in Cornwall.
"But 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. Plus we could see increases of methane emissions at the same time.
"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."
The story behind the study
This study took researchers on an unexpected journey that included COVID lockdowns, polar bear safety training and dragging a canoe overland.
Like many research projects, it started with pilot studies – one extracting and analysing peatland samples in Canada and Finland, the other testing "remote sensing" with drones and satellites.
The team wanted to combine these to find out how climate change is affecting Arctic peatlands. They started applying for funding in 2013, and got their first rejection in 2015. Two more rejections came the following year. In 2018, they finally got a grant – and the project started in summer 2019.
Dr Crichton used Google Earth Engine to identify possible study sites, and Professor Angela Gallego-Sala went on the first fieldwork expedition – to Svalbard, where she received training on avoiding encounters with hungry polar bears.
With the research finally making progress, COVID lockdowns halted fieldwork and lab work. While this hampered the project, Dr Crichton's computer-based work could continue. "I was still at my desk using Google Earth Engine," she said. "Lockdown didn't make any difference to the work I was doing."
So Dr Crichton continued identifying fieldwork sites, analysing data and applying for permits – paving the way for fieldwork in Canada in 2021-22. On one of those expeditions, Professor Gallego-Sala stayed at a basic research station on Bylot Island where the washing facility was a "half-frozen lake". She said: "It was light all the time. You could do fieldwork all day long and all night if you wanted to."
From that research station, the team visited remote sites via helicopter. Many sites had no name, and the pilot wanted names in order to arrange pick-ups – so sites got informal names including "Glacial Nirvana" and "Angela's Paradise". At each site, the team extracted peatland cores to learn about the history of the peatland and how it might be changing.
At Salluit in northern Canada, the team had an Inuit guide for expeditions out into the peatland – during which they saw wildlife including black bears and reindeer, and caught fish and mussels for dinner each evening. When the team laid out their plan one day, the guide shrugged and said: "You can go wherever you want." He did not mention that their plan would leave their canoe stuck on a large area of sand at low tide.
The three female researchers had to push the stranded boat overland, while the guide sat in it. "We pushed it a long way through the sand," Professor Gallego-Sala said. "It was pretty tough – but it was also hilarious, and we managed to get it out."
"Meanwhile, I'm still sat at my computer by the way," said Dr Crichton, laughing. But this work provided a crucial component – allowing comparison between peatland cores and long-term satellite data that shows peatland edges getting greener as vegetation spreads.
Professor Gallego-Sala added: "Going out for fieldwork is a short time in comparison to the rest of the work. There is lots of lab work to analyse the samples, then extensive data analysis before the findings can be written into a published paper."
The study is part of a project called Increased Accumulation in Arctic Peatlands (ICAAP), funded by the Natural Environment Research Council.
The paper, published in the journal Communications Earth and Environment, is entitled: "Satellite data indicates recent Arctic peatland expansion with warming."
