District-level assessment of the ecohydrological resilience to hydroclimatic disturbances and its controlling factors in India

The carbon and water cycles play an important role in ecosystem functioning and are linked to each other through different physical and biological processes. The hydroclimatic disturbances such as droughts affect both hydrological as well as the ecological processes. Increasing hydroclimatic disturbances under climate change will adversely affect the ecohydrological processes and hence, the assessment of the ecohydrological resilience and its controlling factors is important for the sustainability of the ecosystems. In this study, an assessment of the resilience of terrestrial ecosystems in India to hydroclimatic disturbances was carried out at the district (i.e. administrative division) scale. Ecosystem water use efficiency (WUEe ), defined as the ratio of net primary productivity (NPP) to evapotranspiration, was used as an indicator of ecosystem functioning or its response to hydroclimatic disturbances. We found a large spatial variation in WUEe in India at district scale, which was significantly higher in lower Himalayan regions compared to rest of the country. Increasing trend in WUEe was found for central parts of the country. The resilience was measured in terms of the ratio of the WUEe under the dry conditions and the mean WUEe , which indicates the ability to absorb hydroclimatic disturbance. Out of 634 districts considered for this study, only 241 (~38%) districts were found resilient to dry conditions, whereas a significant reduction in WUEe was observed for some of the districts. The resilience at district scale indicates the cross-biomes response of ecosystems. In general, the forest dominated districts had higher resilience compared to districts dominated by other biome types. Also, districts having temperate climate were found having higher resilience. Out of 30 states and union territories (UTs) only 10 states had more than 50% resilient area. The results of this study highlight the need for better ecosystem management policies in the country.