Wild bee fauna in apple orchards: effects of managed bee populations and surrounding landscape

Summary

Insects, including bees, play a vital role in pollination, which is essential for plant reproduction and agricultural food production. However, bee populations have experienced significant declines in the last few decades due to various anthropogenic factors such as intensified agriculture, habitat loss, and climate change. In Switzerland, nearly 600 wild bee species exist, with 45% of all native bee species at risk and 60 species already extinct. Therefore, the introduction of managed bees, such as honeybees and managed mason bees, into agricultural ecosystems has increased to supplement wild bee pollination. Given the importance of apple production in Switzerland, understanding the impact of different factors on wild bee populations in apple orchards is crucial. This study sought to explore how managed bees, the surrounding landscape, and cultivation types can impact the abundance and species richness of wild bees in Swiss apple orchards. Understanding these relationships can help in developing effective conservation and management strategies to enhance wild bee populations, which, in turn, can positively impact apple production. The study was conducted within 15 different apple orchards across Switzerland, the bee occurrence was measured with pan traps. Simultaneously, drone recordings were used to map the landscape within a 500 m radius to identify nesting structures as well as foraging and habitat opportunities for wild bees. The findings of this study indicate that the presence of managed mason bees, may have a negative impact on the abundance and species richness of wild bees in Swiss apple orchards. This suggests that the management of managed bee populations needs to be carefully considered in order to avoid disrupting the wild bee populations in these orchards. Further, the relationship between wild bee populations and the surrounding landscape in the studied apple orchards may be more complex than previously thought, with structural features potentially playing a more important role than overall land use in influencing wild bee populations. These findings emphasize the need for conservation efforts and the provision of suitable habitats to maintain and enhance wild bee populations, which are crucial for the pollination of apple orchards in Switzerland.