Global projection of potential effects of future air quality on bee visual navigation

Airborne aerosols can alter incoming solar radiation inducing different radiative responses, yet the potential ecological effects of changes in the degree of linear polarization (DoLP) by the light alteration remain largely unknown. Light polarization is an important navigational cue for honeybee for which a threshold intensity (i.e., the DoLP) for a reliable response is known as 15%. Here, we quantify the relationship between the mass concentration of airborne fine particulate matter (PM2.5) and the DoLP by ground-based observation to provide an estimate of how the quantity of PM2.5 changes the DoLP in general and how these changes will impair navigation of honeybee by limited-visibility at the global level. We find that the PM2.5 mass concentration exponentially decreases the DoLP, reducing the average and maximum DoLP, and the size of area containing perceivable polarization information by honeybee over the sky. Applying these results to global air quality prediction models, EMAC, MPI-ESM1.2-HAM, MIROC-ES2 under a BaU (for EMAC) and SSP370 (for MPI-ESM1.2-HAM, MIROC-ES2L) scenario, we find that projected areas and the number of days of limited-visibility that honeybee experience increases globally on average. Our estimates capture almost year-round risk hotspots of limited-visibility over sub-Saharan Africa, Eastern Mediterranean, Southeast Asian regions in 2050. In particular, India is projected to experience approximately a 10 folds increase in the number of days of limited visibility. Developing countries are more vulnerable to degrading air quality than developed countries in terms of limited-visibility for honey bees. Overall, our study demonstrates degrading air quality in 2050 as a result of business-as-usual emissions of air pollutants can affect bee navigation, threatening fundamental plant-pollinator interactions. Further, warming climate will exacerbate this impact.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2022-00155875).