A climate-driven environmental sustainability indicator for assessing future Phlebotomus expansion risk in semi-arid Iran

Climate change can redistribute environmentally suitable conditions for Phlebotomus vectors in semi-arid regions, but conventional habitat-suitability models provide limited information on the broader environmental dimensions of future expansion. This study developed a Climate-Driven Environmental Sustainability Indicator (ESI) to assess spatial patterns of future Phlebotomus expansion risk in semi-arid Iran. We analyzed 312 spatially filtered occurrence records and environmental predictors using MaxEnt. Future suitability was projected for 2041–2060 under SSP2-4.5 and SSP5-8.5 using an ensemble of five CMIP6 climate models. The ESI integrated habitat suitability, climate exposure, habitat expansion potential, and environmental vulnerability. Model performance, spatial validation, inter-model variability, and predictor sensitivity were assessed. The model showed strong predictive performance (mean test AUC: 0.942 ± 0.018). Mean Temperature of the Driest Quarter was the largest relative contributor (38.4%). Suitable habitat increased by 25,400 km 2 under SSP2-4.5 and 51,200 km 2 under SSP5-8.5, with northward and elevational shifts. High-to-Very-High ESI areas increased from 20.7% at baseline to 28.0% and 38.9%, respectively. Expansion was concentrated mainly in northern and transitional environments, whereas contraction occurred in hyper-arid southern areas. The ESI provides a transparent framework for translating climate-driven suitability changes into multidimensional environmental expansion-risk assessment while incorporating uncertainty. It does not represent disease transmission probability.