Habitat Quality Assessment Within Expanded Ranges of Dengue Vectors Using a Composite Index Scale

As climate change drives shifts in species distributions, understanding the habitat quality within expanded ranges (defined as newly suitable areas (km²) under future climate scenarios compared to the past baseline, identified using a ≥ 0.5 suitability threshold) remains a critical gap in accurately assessing disease vector risk. Although many studies focus on the geographic range expansion of Aedes species under future climate scenarios, it remains unclear whether these expanded ranges possess the habitat quality necessary for stable mosquito populations. Using MaxEnt modeling, we projected habitat suitability across historical and future climate scenarios (SSP1-4) and applied a Composite Index Scale (CIS) to quantify habitat quality within Asia. Results indicate that, in the past, habitat vulnerability for Aedes aegypti and A. albopictus was 1,698,972 km² and 1,328,577 km², respectively. Future projections suggest that vulnerable suitable habitat areas for A. aegypti will increase to between 1,991,596 km² and 2,220,554 km² by the end of the 21st century. In contrast, the expected rise in suitable areas for A. albopictus will be between 1,589,240 km² and 1,734,846 km². We propose the CIS, which incorporates normalized bioclimatic suitability, habitat suitability changes, niche breadth, niche position, and range shifts, as a refined measure to better quantify habitat quality. Findings reveal that 12 of the 16 scenarios showed improved habitat quality for A. aegypti, highlighting an elevated risk of dengue transmission. For A. albopictus, 10 of the 16 scenarios demonstrated high vulnerability due to favorable habitat quality as predicted by the CIS. A significant correlation was found between CIS values and the number of vulnerable pixels with values ≥ 0.5, highlighting the effectiveness of the CIS as a robust indicator for habitat quality assessment and associated risk.