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Increased concentration of airborne particulate matter (PM) in the atmosphere alters the degree of polarization of skylight which is used by honeybees for navigation during their foraging trips. However, little has empirically shown whether poor air quality indeed affects foraging performance (foraging trip duration) of honeybee. Here, we show apparent increases in the average duration of honeybee foraging during and after a heavy air pollution event compared with that of the pre‐event period. The average foraging duration of honeybees during the event increased by 32 min compared with the pre‐event conditions, indicating that 71% more time was spent on foraging. Moreover, the average foraging duration measured after the event did not recover to its pre‐event level. We further investigated whether an optical property (Depolarization Ratio, DR) of dominant PM in the atmosphere and level of air pollution (fine PM mass concentration) affect foraging trip duration. The result demonstrates the DR and fine PM mass concentration have significant effects on honeybee foraging trip duration. Foraging trip duration increases with decreasing DR while it increases with increasing fine PM mass concentration. In addition, the effects of fine PM mass concentration are synergistic with overcast skies. Our study implies that poor air quality could pose a new threat to bee foraging.

Background: Though the biomass of floral vegetation in understory plant communities in a forested ecosystem only accounts for less than 1% of the total biomass of a forest, they contain most of the floral resources of a forest. The diversity of understory honey plants determines visitation rate of pollinators such as honey bee (Apis mellifera) as they provide rich food resources. Since the flower visitation and foraging activity of pollinators lead to the provision of pollination service, it also means the enhancement of plant-pollinator relationship. Therefore, an appropriate management scheme for understory vegetation is essential in order to conserve pollinator population that is decreasing due to habitat destruction and disease infection. This research examined the diversity of understory honey plant and studied how it is related to environmental variables such as (1) canopy density, (2) horizontal heterogeneity of canopy surface height, (3) slope gradient, and (4) distance from roads. Vegetation survey data of 39 plots of mixed forests in Chuncheon, Korea, were used, and possible management practices for understory vegetation were suggested. Results: This study found that 113 species among 141 species of honey plant of the forests were classified as understory vegetation. Also, the understory honey plant diversity is significantly positively correlated with distance from the nearest road and horizontal heterogeneity of canopy surface height and negatively correlated with canopy density. Conclusions: The diversity of understory honey plant vegetation is correlated to vegetation structure and human impact. In order to enhance the diversity of understory honey plant, management of density and height of canopy is necessary. This study suggests that improved diversity of canopy cover through thinning of overstory vegetation can increase the diversity of understory honey plant species.

<p>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.</p> <p>This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2022-00155875).</p>