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| Bees as polinator (image credited by wikimedia.org) |
Bees play a crucial role in pollinating crops and wild plants, making them essential for biodiversity and food production. However, pesticide exposure is one of the major environmental stressors affecting bee health, particularly in landscapes modified by human activities. While much research has focused on honey bees (Apis mellifera), there's a growing need to understand the impact on non-Apis bees, which include bumble bees, stingless bees, and solitary bees. These species have different ecological traits and varying levels of sensitivity to pesticides, highlighting the need for targeted research and mitigation strategies.
Pesticide Exposure Pathways
Non-Apis bees are exposed to pesticides through various pathways. They come into contact with pesticides in the environment during foraging, nest construction, brood care, and hibernation. Exposure can occur through oral intake of contaminated nectar, pollen, water, or honeydew, and through contact with pesticide residues on plants, soil, and nesting materials. The type and extent of exposure depend on the bees' foraging habits, nesting ecology, and the spatial and temporal patterns of pesticide use in their habitats.
Different bee species exhibit unique ecological traits that influence their pesticide exposure and susceptibility. For instance, solitary ground-nesting bees, which make up approximately 75% of the 20,000 bee species worldwide, are particularly vulnerable to soil-borne pesticides. These bees often excavate nests in the ground, exposing them to pesticide residues in the soil. Conversely, bumble bees and other social bees that nest in cavities or above ground may face different exposure risks based on their nesting materials and foraging behaviors.
Effects of Pesticides on Non-Apis Bees
Pesticides can have lethal and sublethal effects on bees. Lethal effects include direct mortality from acute or chronic exposure, while sublethal effects may impair bees' behavior, physiology, and reproductive success. Sublethal impacts can include reduced foraging efficiency, impaired navigation and memory, decreased reproductive output, and altered social behavior. These effects can cumulatively affect bee populations and the ecosystem services they provide, such as pollination.
Research Gaps and Future Directions
Despite increased research on non-Apis bees, significant gaps remain in our understanding of their pesticide exposure and effects. Current studies often focus on a limited number of species and pesticide types, mainly neonicotinoids. More comprehensive research is needed to cover a broader range of bee species and pesticides, considering the diverse ecological traits and behaviors of non-Apis bees.
Future research should prioritize:
- Diverse Model Species: Expanding studies to include a variety of non-Apis bee species that represent different ecological niches.
- Exposure Pathways: Understanding the specific exposure pathways and environmental contexts that affect different bee species.
- Sublethal Effects: Investigating the sublethal effects of pesticides on bee behavior, physiology, and reproductive success under realistic field conditions.
- Landscape-Level Studies: Conducting landscape-level studies to assess the cumulative impacts of pesticide exposure across different habitats and seasons.
- Integrated Pest Management (IPM): Developing and promoting IPM practices that minimize pesticide use and exposure while maintaining agricultural productivity.
Effective conservation of non-Apis bees requires informed policy decisions based on robust scientific evidence. Environmental risk assessments (ERAs) for pesticides should incorporate data on non-Apis bees, considering their unique vulnerabilities and exposure pathways. Policies should also promote habitat conservation and restoration, providing bees with safe nesting sites and diverse floral resources.
Understanding and mitigating the impacts of pesticides on non-Apis bees is crucial for preserving biodiversity and ensuring sustainable agricultural practices. By addressing research gaps and implementing targeted conservation strategies, we can protect these vital pollinators and the ecosystems they support.
For more detailed information on pesticide exposure and its effects on non-Apis bees, and to explore further research and policy recommendations, visit our website.
Source: Raine, N. E., & Rundlöf, M. (2024). Pesticide Exposure and Effects on Non-Apis Bees. *Annual Review of Entomology*, 69, 551-576. doi:10.1146/annurev-ento-040323-020625. Licensed under a Creative Commons Attribution 4.0 International License.