A new study using data from the Met Office radar network has shed stark light on the dramatic decline of nocturnal flying insects across the UK, particularly in northern regions. Scientists say this phenomenon signals troubling changes to insect populations and the wider ecosystems they support.
Researchers from University of Leeds repurposed data from the Met Office’s 15 weather surveillance radars—originally designed for precipitation and cloud tracking—to detect airborne insects hundreds of times a day. Their analysis, covering the period from 2014 to 2021, reveals that while daytime insect numbers remained stable or even increased in southern regions, night-flying insect counts dropped significantly overall—especially in the UK’s far north.
The team estimated that during the day, roughly 11.2 trillion insects were airborne between 500–700 metres above ground, compared with just over 5 trillion at night. The disparity is not just one of numbers but geography too: nocturnal insect abundance fell more markedly in intensively farmed areas and in places with high levels of artificial nighttime lighting.
One of the lead researchers, Mansi Mungee—formerly at Leeds and now at Azim Premji University in India—described the study as “a crucial step toward understanding where to focus conservation efforts.” She explained that this is among the first studies to show how day- and night-flying insects are being affected differently and how their habitats influence those patterns.
The findings highlight two major drivers. First, artificial light at night, already known to disrupt insect behaviour, may be contributing to the nocturnal decline. “It could be a blip, but there’s also a shift in the way we are lighting the night, in terms of the types of bulbs and car headlights getting brighter,” said co-author Christopher Hassall. Second, the decline in northern species is likely linked to climate change: as environments become warmer and drier, species adapted to cooler northern regions may shrink or disappear, while southern species lag behind in filling the gap. “The northern species will be declining because it’s getting too warm and too dry for them,” Hassall noted.
Interestingly, the research found insect abundance was higher in urban areas and landscapes with woodlands or grasslands, and lower in intensively farmed regions—suggesting that habitat diversity and green space may help support flying insect populations.
The study focuses on raw insect abundance rather than species diversity—a caveat acknowledged by the authors. However, the use of radar data offers an innovative way to monitor insects on a large scale bypassing some of the limitations of traditional citizen-science biodiversity monitoring.
These revelations come at a time when concerns about global insect declines and their knock-on effects on pollination, food webs and broader ecosystem services are rising. While much attention has focused on daytime pollinators and ground-dwelling species, this work shines a spotlight on the invisible world of nocturnal insects and highlights an urgent need to understand and address the forces driving their disappearance.
For conservation and policy makers, the message is clear: preserving night-time insect populations may require addressing light pollution, restoring habitat heterogeneity in agriculture, and factoring in climate-driven range shifts. Without action, the silent flight of countless insects across UK skies may become a thing of the past.
