COS 141-1 - Broad scale monitoring of aerial insect abundance using dual polarization weather radar

Abstract: There are increasing concerns about possible declines in the abundance and biodiversity of insects, and in the ecosystem services they provide. However, the evidence base for such dynamics remains sparse and inconsistent due to the scarcity of data, as most entomological data are time consuming and expensive to collect. The growing global network of sophisticated weather radars provides a promising new source of entomological information. Each radar facility collects data on airborne material over thousands of km² every few minutes, providing information not only about the amount of material in the air column, but also on the size, shape and diversity of objects detected. This allows insects to be distinguished both from precipitation and from larger flying animals.
Here, we describe local and regional trends in insect abundance and biomass using data from dual-polarization weather radars in the UK. Firstly, we validate the use of weather radar data at local scale by demonstrating strong correlations between radar reflectance patterns and near-ground point insect samples (moth light traps and broad-spectrum suction traps). Moreover, abrupt shifts in radar cluster composition are detected around sunset and sunrise each day, corresponding to shifts in activity between diurnal and nocturnally flying insect taxa. We can then quantify the relationships between insect abundance and regional landscape (e.g. land use, topography) and climate variables across the UK. Finally, we can use the relationship between regional drivers and insect abundance to produce a national map of aerial insect biomass. The predictions from this spatial model can then be validated using standardised monitoring data. We will close by discussing how these novel biomass measures can be compared to patterns in insect-based functions and services, e.g. crop pest and biocontrol patterns and aerial insectivore population performance. In a few cases, it may even be possible to do species-level aerial monitoring; for example tracking locust swarms and seasonal migration and emergence events. Ultimately, repeated assessments across time and space will allow the dynamics of airborne insect populations and communities to be followed, and their responses to putative drivers and mitigation actions to be assessed. Radar-based insect monitoring thus provides an exciting new tool for monitoring the nature, causes, and consequences of insect declines at unprecedented scales.