Abstract
Rice-crab co-culture is a representative ecological circular farming system, yet its water and energy requirements and associated emissions remain insufficiently quantified under contrasting irrigation strategies. Here, we combined a three-year field experiment in Heilongjiang Province, Northeast China, with life cycle assessment to quantify partitioned water inputs (rice irrigation and crab-related exchange), energy demand, greenhouse gas emissions, and economic performance under water-saving versus flooded co-culture management. Across the three experimental years, water-saving co-culture reduced rice irrigation by 24.7–26.0% and crab exchange water by 36–37% compared with flooded co-culture. It also reduced total carbon footprint by 32.5% and decreased carbon footprint per unit output value by 35.1%, indicating improved climate efficiency per economic output. Nonrenewable energy consumption was lower under water-saving co-culture, while revenues increased over the three experimental years, indicating an association between water-saving management and improved resource-use and economic performance. Overall, our results provide field-based evidence that optimizing water-level management in habitat-constrained rice-crab systems can simultaneously reduce water and energy inputs and emissions, offering transferable insights for irrigated rice-aquatic production under increasing water and energy constraints.