Land-use intensification threatens biodiversity as humans have rapidly transformed the global environment for food production. Generally, agricultural habitats have lower taxonomic diversity and different community composition compared with natural habitats, although the magnitude of changes varies greatly among studies, and the effect on other facets of diversity remain unclear. Given that agricultural land area is expected to increase in the future, it is crucial to understand their ecological impacts on biodiversity. To understand the consequences of agricultural expansion on bee diversity, we collected bee trait and community composition data globally. We examined if taxonomic and functional diversity estimates were higher in semi-natural habitats compared to agricultural habitats, and in sites adjacent to semi-natural habitats. As agricultural landscapes contain sites with different management strategies, which potentially lead to variable bee diversity patterns, we included enhancement habitats, field margins, organic and conventional farms to assess diversity differences between agricultural and semi-natural habitats.
Results/Conclusions
Here, we provide results based on 635 communities from 33 studies documenting bee communities in agricultural and semi-natural habitats. Surprisingly, there was no significant difference in taxonomic and functional diversity between semi-natural and all agricultural habitats. However, higher quantities of semi-natural habitats within 1 km of sites significantly increased taxonomic diversity, and to a lesser extent functional diversity. Furthermore, we found that small bees are numerically less abundant in sites isolated from semi-natural habitats, suggesting that the loss of functional diversity is partially contributed by the loss of small bees. Our results highlight the vulnerability of small bees in agricultural expansion, which can be explained by their weaker abilities in collecting resources and recolonizing habitats. Our study also highlights the importance of landscape drivers in determining bee diversity across sites, emphasizing the need to preserve and/or restore semi-natural habitats in agricultural landscapes to increase conservation value.