Drought-induced peatland carbon loss exacerbated by elevated CO<sub>2</sub> and warming.

Quan, Quan; Zhou, Jian; Hanson, Paul J; Ricciuto, Daniel; Sebestyen, Stephen D; Weston, David J; Chanton, Jeffrey P; Wilson, Rachel M et al. · Science · 2025

basic_science · Level V

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Abstract

Extreme drought events are predicted to increase with climate change, yet their impacts on ecosystem carbon dynamics under warming and elevated carbon dioxide (eCO<sub>2</sub>) remain unclear. In a peatland experiment with five warming treatments each under ambient carbon dioxide (aCO<sub>2</sub>) and eCO<sub>2</sub> (+500 parts per million), a 2-month extreme drought in 2021 reduced net ecosystem productivity by 444.0 ± 65.8 and 736.6 ± 57.8 grams of carbon per square meter at +9°C under aCO<sub>2</sub> and eCO<sub>2</sub>, respectively-228.6 ± 56.8% and 381.9 ± 83.4% of the reduction at +0°C under aCO<sub>2</sub>. This exacerbation was driven by warming-induced water table decline, prolonged low water tables, and CO<sub>2</sub>-enhanced substrate availability through increased plant carbon inputs. Findings indicate that future climate will greatly amplify carbon loss during extreme drought, reinforcing positive carbon-climate feedbacks.