Weather radar data reveal alarming declines in insect populations

A research team including a Keele University scientist have made a breakthrough in monitoring insect populations across the UK using weather radar data. Traditionally used to track rainfall and storms, these radars are now helping researchers monitor the daily movements and long-term numbers of flying and floating creatures—including bees, moths, flies, spiders, and other arthropods.

The study, published in Global Change Biology, examined radar data collected between 2014 and 2021 over 35,000 square kilometers of the UK. It found that while daytime insect numbers have remained relatively stable or even increased in southern regions, nighttime-airborne insects have declined overall—especially in the far north.

The data also showed that nocturnal arthropods such as moths have significantly declined over time, and areas with more light pollution showed lower night-time and day-time insect activity. Overall, there are more insects in landscapes dominated by woodland and cities, while there are fewer insects on farmland.

Professor James Bell, Professor of Entomology at Keele University and co-author of the study, said the new application for weather radar gives researchers “an unprecedented opportunity” to understand Earth’s diverse insects.

Professor Bell said, “For every human on Earth, there are 1.4 billion insects of which we know almost nothing. Long-distance insect migration is often misunderstood, an essential but often obscured component of the life cycle of these small animals.”

The new work supports Professor Bell’s previous findings, in collaboration with the Rothamsted Insect Survey, which revealed a 31% decline in nocturnal moth numbers between 1969 and 2016, partly driven by light pollution which profoundly alters their movement behavior.

Lead author Dr. Mansi Mungee, now at Azim Premji University, said, “This is one of the first studies to show how day and night-flying insects are being affected differently, and how their habitats influence those patterns. It’s a crucial step toward understanding where to focus conservation efforts.”

Using weather radar to monitor insects has huge potential for conservation and ecology by enabling cost-effective, scalable methods of biodiversity tracking. This data can also be used to inform strategies to lessen insect declines, as well as contribute to urban planning by revealing surprising insect hotspots in cities.

Co-author Dr. Christopher Hassall from the University of Leeds, added, “We’d like this research to contribute new insect metrics from radar to the UK Government’s biodiversity indicators, showing us how changes to landscape management affect insects.”

Insects may be small, but their impact on ecosystems is huge. They pollinate crops, break down waste, and are vital food for birds, bats, and other wildlife. Changes in their numbers can ripple through entire ecosystems.

Dr. Ryan Neely, Associate Professor of Observational Atmospheric Science at the National Centre for Atmospheric Science and the University of Leeds and co-author of the study said, “Arthropods make up around 80% of all known animal species, yet we’ve lacked consistent, large-scale tools to monitor them. This new weather radar-based approach changes that.”

The team, led by Dr. Mungee, repurposed data from the UK’s network of weather surveillance radars, which scan the sky hundreds of times a day. Using new radar technology that emits two different beams during a scan (known as “dual polarization”) and measuring how those signals are scattered back, the researchers were able to tell insects apart from raindrops and estimate the number of insects flying between 500 and 700 meters above ground.

Their results show an average of 11.2 trillion insects in the air during daytime hours and just over 5 trillion at night during the main flying seasons. Insect abundance was higher in areas with woodlands, grasslands, and even urban areas—but dropped in intensively farmed regions and where artificial lighting was high.

Dr. Hassall added, “As an ecologist I am fascinated by what weather scientists do, because their work is highly technical with advanced equipment, but at the same time, scientists use a lot of intuition and experience to understand complex patterns in the data. We’ve been able to use their wealth of implicit knowledge to interpret the strange features on weather radars, which we now know to be insects.

“Historically, they used to call these features ‘angels’ because radar operators didn’t know what they were. By the 1950s or 60s, there was strong suspicion it was birds and insects, and that grew in the 70s and 80s when they started calling these features ‘bioscatter,’ knowing that it was birds, bugs and bats.

“This study opens a window to a huge and important new source of biodiversity monitoring data. Our findings are just a tantalizing glimpse of what weather radar data can reveal for ecologists.”