Nocturnal Arthropod Declines Unveiled by Weather Radars at a National Scale

Arthropod declines have been widely reported; however, a lack of comprehensive data has hindered our ability to assess their large-scale generality and drivers. Here, we used a novel and freely available dataset – atmospheric scans from a network of meteorological radars – to quantify high resolution aerial abundance of both, diurnal and nocturnal arthropods across the United Kingdom. Using observations between 2014 and 2021, and covering >42,000 km², we estimated that at least 2.31(±1.28) quadrillion arthropods fly over the UK each year, with high vertical and spatial heterogeneity. Our analysis revealed a widespread decline in nocturnal, but not diurnal arthropods. Furthermore, we observed more pronounced losses in northern latitudes, for both diurnal and nocturnal arthropods, attributed to changes in light pollution, land cover, and weather. While previous studies have reported declines in specific species and places, our study reveals broadscale and widespread losses, especially in the abundance of nocturnal aerial arthropods, and highlights the importance of considering spatial variation in temporal biodiversity trends. Additionally, we demonstrate the potential for weather radar datasets to enhance understanding of biodiversity decline trends and causes at fine resolution across large spatio-temporal extents.