Assessment of district scale ecosystem health in India using multi decadal carbon and water use efficiencies

Ecosystem health assessments are critical for understanding ecosystem functioning under increasing climatic and anthropogenic stress, particularly across India’s heterogeneous landscapes. Here, we present a district-scale assessment (n = 640) integrating carbon use efficiency (CUE) and water use efficiency (WUE) over 1982–2018 to quantify spatial patterns, trade-offs, long-term evolution, and drought responses. District-mean CUE ranges from ~ 0.35 to 0.60, while WUE exhibits strong aridity-driven gradients, with higher values in humid and irrigated regions and lower values in arid districts. We estimate long-term trends and resilience using lag-1 temporal autocorrelation and classify ecosystem health based on combined changes in CUE and WUE. Approximately 55–60% of districts show increasing trends in both efficiencies, although these gains are frequently accompanied by rising evapotranspiration (ET), particularly in cropland-dominated districts, indicating growing water demand. Trade-offs between CUE and WUE are pronounced across land-cover and aridity gradients, with humid districts exhibiting higher CUE but lower WUE, and semi-arid districts prioritizing water-use efficiency. Extreme drought years, identified using climatic water deficit, lead to widespread declines in WUE across over two-thirds of districts, while CUE responses are more variable and ecosystem-specific. Overall, the results reveal spatially coherent patterns of resilience loss and efficiency trade-offs linked to water availability and management intensity. The proposed framework provides a long-term, district-scale perspective on carbon–water coupling and offers decision-relevant indicators for identifying regions vulnerable to water stress and ecosystem degradation.