Peat fires contribute disproportionately to Siberian fire carbon emissions

Arctic and boreal fires are critical threats to terrestrial carbon reservoirs, particularly peat fires that trigger long-term irrecoverable carbon losses and permafrost thaw. However, the occurrence of peat fires and their associated carbon emissions remain highly uncertain. 30-meter satellite-derived maps of burned area and peatland coverage reveal that Siberian fires burned over 107 million hectares during the 2001 to 2023 period, with peat fires accounting for up to one-third of this area. These peat fires emitted 1.24 ± 0.06 petagram of carbon, largely exceeding conventional datasets' estimates. We found that anomalous dry and warm climatic conditions represent the primary driver of extreme peat fire seasons and that overwintering of 2020's late-season peat fires substantially contributed to extensive fires of 2021. Peat fires, especially those in Arctic regions, exhibit a pronounced sensitivity to extreme weather, posing a critical threat to the stability of permafrost peatlands and their large carbon stocks.