Climate-driven shifts in lumpy skin disease risk across Iran: Insights from ensemble species distribution models

This study aimed to identify the environmental determinants influencing the distribution of lumpy skin disease and to predict changes in its spatial distribution risk and potential geographic range across Iran under future climate change scenarios using ensemble Species Distribution Models (SDMs). To this end, following data cleaning and quality control of 3654 disease occurrence records, a total of 2849 presence points recorded between 2013 and 2024 were retained for model development. The CTA, GAM, GBM, and RF algorithms were implemented within an ensemble modelling framework. The final ensemble model (EMca) achieved a True Skill Statistic (TSS) score of 0.85, an area under the receiver operating characteristic curve (AUC) of 0.96, and a Boyce index of 0.96 during calibration. For the validation data, the corresponding scores were 0.66, 0.89, and 0.93, respectively. The model therefore demonstrated broadly consistent predictive performance across calibration and validation based on these three evaluation metrics. Future projections were generated using three General Circulation Models (GCMs) HadGEM3-GC31-LL, MIROC6, and MPI-ESM1-2-HR under the SSP2-4.5 and SSP5-8.5 climate scenarios for the 2021-2040 and 2041-2060 time periods. The results indicated that hydrological, anthropogenic, and climatic variables were the three primary determinants of the spatial distribution of lumpy skin disease. Among the predictor variables, distance to rivers, distance to roads, and annual precipitation were identified as the most influential factors governing disease distribution, respectively. Furthermore, the risk maps revealed that western and northwestern Iran, together with the Zagros Mountain Range, which currently represent the principal disease hotspots, are projected to remain the major potential hotspots under future climate change scenarios. Range size analysis further indicated that although a proportion of the currently suitable areas for lumpy skin disease is projected to be lost under future climate conditions, the emergence of newly suitable areas is expected to largely offset these losses. Consequently, the net change in the disease's potential range is predicted to be minimal during the 2021-2040 period (-0.98%). However, this decline is projected to increase to -4.34% under the SSP2-4.5 scenario and -8.01% under the SSP5-8.5 scenario during the 2041-2060 period. Overall, the findings suggest that, in the near future, climate change is more likely to drive a spatial reorganization of disease risk hotspots than to cause a substantial expansion of the disease's potential distribution. These findings provide a robust scientific basis for targeted surveillance, strategic vaccination, and the development of early warning systems for the effective management of lumpy skin disease in Iran.