Drivers of nocturnal and diurnal insect declines in urban landscapes

Le résumé fourni par la source

Insect pollinators are essential for the health and resilience of terrestrial ecosystems, delivering key ecosystem services in the face of anthropogenic disturbance. Urbanisation may be a key threat to pollinator diversity and abundance. However, the scale of the threat remains unknown due to an overwhelming research emphasis on bees and a lack of comparative studies of hyper-diverse taxa such as nocturnal moths. Consequently, the question of which pollinator groups will be more affected by urbanisation remains unknown, and the habitat features that support key taxa remain controversial. We conducted the first large-scale assessment of the negative effects of increasing urbanisation on the diversity of bee, hoverfly and nocturnal moths across three cities. We report up to a 43% reduction in species richness along replicated urbanisation gradients, suggesting that a wide range of pollinators are limited due to abiotic stresses and limited resources in urban environments. Landscape mapping indicated that these effects are driven by the reduction of tree cover and semi-natural habitat; however, the specific landscape drivers were taxon-specific, suggesting that urban insect conservation depends on the preservation or expansion of habitat features specific to different threatened taxa. In the first empirical comparison of three major pollinator taxa, we show that, relative to bees, moths and hoverflies are particularly sensitive to urbanisation, and we highlight the importance of including these frequently overlooked pollinator groups when assessing the biodiversity impacts of environmental change.

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