Spatial Landscape and Ecosystem Services Assessment of a Dryland Reservoir–Watershed System

Abstract

Dryland reservoir–watershed systems face multiple environmental pressures, including water scarcity, anthropogenic land conversion, and increasing demands for sustainable ecosystem management. Nevertheless, ecological assessments of these systems frequently remain disconnected from their surrounding landscape context, limiting their relevance for integrated watershed management. To address this gap, this study employs a spatially explicit ecosystem-service assessment framework to quantify carbon storage and habitat quality across the Shahid Shahcheraghi reservoir–watershed system in northeastern Iran. A seven-class land use/land cover (LULC) map for 2025 was generated and used as the primary input for the InVEST Carbon and Habitat Quality models. Total carbon storage was estimated at approximately 39.37 million Mg C, with soil organic carbon constituting the dominant pool (74.3%), followed by belowground biomass (17.1%) and aboveground biomass (8.4%). Spatially, carbon storage was generally higher in areas with greater vegetation cover. Habitat quality, by contrast, revealed a markedly asymmetric distribution: the mean habitat quality index was 0.27, with 70.7% of the study area classified as having very poor habitat quality, whereas 22.9% fell within the good to excellent categories. High-quality habitats were predominantly concentrated in mountainous areas characterized by extensive grasslands and tree/shrub cover, while low-quality areas were concentrated in developed and highly accessible zones subject to greater anthropogenic disturbance. These findings reveal pronounced spatial heterogeneity in ecological condition and demonstrate that integrating readily available geospatial data with the InVEST modelling framework can provide a replicable and cost-effective approach for assessing ecosystem condition in data-limited dryland environments.