Nature Geoscience Manuscript NGS-2020-12-02844A

Tropical peatlands are threatened by climate and land-cover changes but there remain substantial uncertainties about their present and future role in the regional and global greenhouse gas (GHG) budgets due to limited measurements. Measurements from a peatland in Sumatra, Indonesia, indicate that the radiative balance for sustained flux of carbon dioxide, methane and nitrous oxide over a 100-year period increased from 21.0 ± 4.5 tCO₂e ha⁻¹ yr⁻¹ (average ± standard deviation) at the intact site to 44.4 ± 1.5 tCO₂e ha⁻¹ yr⁻¹ at the degraded site. The significant carbon dioxide emissions from the intact site, during an extreme drought caused by a positive Indian Ocean Dipole phase combined with El Niño, highlight the potential importance of climate regime in determining the GHG budget of tropical peatlands. Reducing GHG emissions from these globally important ecosystems is of increasing importance in the context of climate change mitigation. Here, we show that protecting the remaining intact tropical peatlands from degradation offers a viable way to avoid significant radiative forcing, which for our study in Sumatra was 23 ± 5 tCO₂e ha⁻¹ yr⁻¹.