Progressive release of long-stored carbon from tropical peatland disturbances

Koarashi, Jun   ; Ito, Masayuki*; Atarashi-Andoh, Mariko  ; Kokubu, Yoko   ; Matsueda, Makoto   ; Kusin, K.*; Jaya, A.*; Dohong, S.*; Hirano, Takashi*

Tropical peatlands are globally important, millennia-old carbon sinks, yet unprecedented human-driven degradation is triggering alarming carbon emissions. Comprehensive quantification of carbon dynamics across the disturbance sequence, from peat swamp forests to drained and fire-impacted peatlands, remains a critical knowledge gap. Here we show that over 18 years (1996-2014), drainage and subsequent peat fires released approximately 30-41 kg C m from peatlands in Central Kalimantan, Indonesia, using radiocarbon dating of peat profiles and groundwater dissolved organic carbon. Drainage contributed 5-11 kg C m, primarily from centuries- to millennium-old, previously waterlogged peat. Fires released 23-32 kg C m from peat accumulated over the past 3,000 years, initiating progressive oxidative decomposition of older peat. Extrapolation to Indonesia's disturbed peatlands suggests a release of 0.81-3.70 Gt between 1996 and 2014, with ongoing decomposition releasing an additional 0.03-0.08 Gt C annually, accelerating the impact on the global carbon balance.