Online Supplement for Adaptive Irrigation Management Significantly Reduces GHG Emissions and Increases Yields in Balinese Rice Terraces from Adaptive irrigation management by balinese farmers reduces GHG emissions and increases rice yields

The potential for changes in water management regimes to reduce greenhouse gases (GHG) in rice paddies has recently become a major topic of research in Asia, with implications for top-down versus bottom-up management strategies. Flooded rice paddies are a major source of anthropogenic GHG emissions and are responsible for approximately 11% of global anthropogenic CH₄ emissions. But rice is also the most important food crop for people in low- and lower-middle-income countries. While CH₄ emissions can be reduced by lessening the time the plants are submerged, this can trigger increased emissions of nitrous oxide N₂O, a more potent greenhouse gas. Mitigation options for CH₄ and N₂O are different, and minimizing one gas may increase the emission of the other. Accurate measurement of these gas emissions in rice paddies is difficult, and the results are controversial. We analysed these trade-offs using continuous high-precision measurements in a closed chamber in 2018–2020. Based on the results, we tested a bottom-up adaptive irrigation regime that improves nitrogen uptake by rice plants while reducing combined GHG emissions and nitrogen runoff from paddies to reefs in agricultural drainages. In 2023, we undertook a follow-up study in which farmers obtained higher rice yields with adaptive intermittent irrigation compared to uniformly flooded fields. These results use the polycentric, self-governing capacity of Balinese subaks for continuous adaptation.This article is part of the theme issue ‘Climate change adaptation needs a science of culture’.