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Pollinator assemblages in grasslands along river valleys depend on the urban matrix and local habitat scale variables
Sown wildflower meadows: Can they replace natural meadows in urban spaces for bees, butterflies and hoverflies?
Abstract The decline in pollinator populations is partly due to human practices that have contributed to the loss of wild and flower‐rich habitats. In cities, especially city centres, urban green spaces, which are usually small, are often sown with wildflower meadows. The study compared the number and species richness of three main groups of pollinating insects (wild bees, butterflies and hoverflies) for two types of meadows in Warsaw: sown wildflower meadows and the natural meadows. The research results showed that there was no difference in the composition of insect‐pollinated plants between the meadow types. There was also no difference between the meadow types concerning the species richness of butterflies, bees and hoverflies. However, it was confirmed that the number of butterflies was twice as high in natural meadows than it was in sown floral meadows, while in the case of wild bees and hoverflies, no such differences were found. The study confirmed that areas sown with wildflowers, usually of small area, concentrate pollinating insects and have a similar value for pollinators as larger areas of natural meadow. Sown wildflower meadows, if properly cared for, can ensure the richness of melliferous plant species and thus positively affect the diversity and number of pollinators. Sown meadows can compensate insects for the absence of large, natural meadows, especially in the fragmented spaces in cities.
Land Use Change Consistently Reduces α‐ But Not β‐ and γ‐Diversity of Bees
ABSTRACTLand use change threatens global biodiversity and compromises ecosystem functions, including pollination and food production. Reduced taxonomic α‐diversity is often reported under land use change, yet the impacts could be different at larger spatial scales (i.e., γ‐diversity), either due to reduced β‐diversity amplifying diversity loss or increased β‐diversity dampening diversity loss. Additionally, studies often focus on taxonomic diversity, while other important biodiversity components, including phylogenetic diversity, can exhibit differential responses. Here, we evaluated how agricultural and urban land use alters the taxonomic and phylogenetic α‐, β‐, and γ‐diversity of an important pollinator taxon—bees. Using a multicontinental dataset of 3117 bee assemblages from 157 studies, we found that taxonomic α‐diversity was reduced by 16%–18% in both agricultural and urban habitats relative to natural habitats. Phylogenetic α‐diversity was decreased by 11%–12% in agricultural and urban habitats. Compared with natural habitats, taxonomic and phylogenetic β‐diversity increased by 11% and 6% in urban habitats, respectively, but exhibited no systematic change in agricultural habitats. We detected a 22% decline in taxonomic γ‐diversity and a 17% decline in phylogenetic γ‐diversity in agricultural habitats, but γ‐diversity of urban habitats was not significantly different from natural habitats. These findings highlight the threat of agricultural expansions to large‐scale bee diversity due to systematic γ‐diversity decline. In addition, while both urbanization and agriculture lead to consistent declines in α‐diversity, their impacts on β‐ or γ‐diversity vary, highlighting the need to study the effects of land use change at multiple scales.