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

## TL;DR

This study assesses the quality of new habitats for dengue-carrying mosquitoes under future climate scenarios in Asia, finding increased risk areas and introducing a new index to evaluate habitat quality.

## Contribution

The study introduces a novel Composite Index Scale (CIS) to quantify habitat quality for dengue vectors under climate change scenarios.

## Key findings

- Vulnerable suitable habitat for Aedes aegypti is projected to expand up to 2.22 million km² by the end of the 21st century.
- The Composite Index Scale (CIS) showed strong correlation with habitat vulnerability, indicating its effectiveness in predicting dengue transmission risk.
- 12 of 16 scenarios for A. aegypti and 10 of 16 for A. albopictus showed high vulnerability due to favorable habitat quality.

## Abstract

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.

Using MaxEnt and a novel Composite Index Scale (CIS), we quantified habitat quality for Aedes aegypti and A. albopictus across historical and future (SSP1–4) climate scenarios in Asia. We found that vulnerable suitable habitat areas for A. aegypti and A. albopictus will expand by up to ~2.22 million km2 and ~1.73 million km2, respectively, with 12 of 16 and 10 of 16 scenarios showing high vulnerability. CIS values were strongly correlated with the number of pixels ≥ 0.5, demonstrating its effectiveness as a robust predictor of dengue vector risk.