Biodiversity loss and declines in local insect abundance are an undeniable feature of the Anthropocene. However, estimating the effects of anthropogenic change on insect abundance is challenging because insect time series data are rare, geographically biased, and focus mainly on charismatic taxa. In this study, we used a nation-wide network of weather surveillance radar to provide data on insect abundance at continental scale. We analyzed a 10-year time series of insect density in the sky above the United States, and identified regions of increases and declines.
Continental scale insect density varied strongly between years with no net change over the period 2012-2022. Underlying the net stable pattern was spatial variation between regions of declines and increases. Regionally, declines in insect density were more common in the Central Plains region and along the East coast, while increases mainly occurred in the western United States. Next, we used the national land cover database to analyze change in insect abundance across land cover types. Areas that experienced declines in day-flying insect density in the past decade had higher levels of human development in the landscape. Declines were not associated spatially with crop use, pastures, or forests.
This study provides the first continental scale analysis of the role of land use and anthropogenic change on day-flying insect density. We also demonstrate the utility of weather surveillance radar for large-scale monitoring to provide time series of insect abundance.
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