Wildfires offset the increasing but spatially heterogeneous Arctic–boreal CO2 uptake
Anna‐Maria Virkkala, Brendan M. Rogers, Jennifer D. Watts, Kyle A. Arndt, Stefano Potter, Isabel Wargowsky, Edward A. G. Schuur, Craig R. See, Marguerite Mauritz, Julia Boike, M. Syndonia Bret‐Harte, Eleanor Burke, Arden Burrell, Namyi Chae, Abhishek Chatterjee, Frédéric Chevallier, Torben R. Christensen, R. Commane, A. J. Dolman, Colin W. Edgar, Bo Elberling, Craig A. Emmerton, E. S. Euskirchen, Liang Feng, Mathias Goeckede, Achim Grelle, Manuel Helbig, David Holl, Järvi Järveoja, Sergey V. Karsanaev, Hideki Kobayashi, Lars Kutzbach, Junjie Liu, Ingrid T. Luijkx, Efrèn López‐Blanco, Kyle Lunneberg, Ivan Mammarella, Maija E. Marushchak, Mikhail Mastepanov, Yojiro Matsuura, Trofim Maximov, Lutz Merbold, Gesa Meyer, Mats B. Nilsson, Yosuke Niwa, Walter C. Oechel, Paul I. Palmer, Sang‐Jong Park, Frans‐Jan W. Parmentier, Matthias Peichl, Wouter Peters, Roman Petrov, William L. Quinton, Christian Rödenbeck, Torsten Sachs, Christopher Schulze, Oliver Sonnentag, Vincent L. St. Louis, Eeva‐Stiina Tuittila, Masahito Ueyama, Andrej Varlagin, Donatella Zona, Susan M. Natali
Abstract
Abstract The Arctic–Boreal Zone is rapidly warming, impacting its large soil carbon stocks. Here we use a new compilation of terrestrial ecosystem CO 2 fluxes, geospatial datasets and random forest models to show that although the Arctic–Boreal Zone was overall an increasing terrestrial CO 2 sink from 2001 to 2020 (mean ± standard deviation in net ecosystem exchange, −548 ± 140 Tg C yr −1 ; trend, −14 Tg C yr −1 ; P < 0.001), more than 30% of the region was a net CO 2 source. Tundra regions may have already started to function on average as CO 2 sources, demonstrating a shift in carbon dynamics. When fire emissions are factored in, the increasing Arctic–Boreal Zone sink is no longer statistically significant (budget, −319 ± 140 Tg C yr −1 ; trend, −9 Tg C yr −1 ), and the permafrost region becomes CO 2 neutral (budget, −24 ± 123 Tg C yr −1 ; trend, −3 Tg C yr −1 ), underscoring the importance of fire in this region.