Scientists have made a breakthrough in monitoring insect population trends across the UK using an unexpected tool: weather radar. Traditionally used to track rainfall and storms, these radars are now helping researchers monitor the daily movements and long-term abundance of flying and floating insects – including bees, moths, flies, spiders, and other arthropods – over thousands of square kilometres.

The study, which examined radar data collected between 2014 and 2021, analysed aerial insect activity over 35,000 square kilometres of the UK. It found that while daytime insect numbers remain relatively stable or even increased in southern regions, nighttime-airborne insects have declined overall – especially in the far north.

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. A drop in their numbers can ripple through entire ecosystems. Despite growing concern about insect declines due to climate change, land use, and light pollution, it’s been difficult to track large-scale trends – until now.

“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,” says Dr Ryan Neely, Associate Professor of Observational Atmospheric Science at the National Centre for Atmospheric Science (NCAS) and the University of Leeds.

The team repurposed data from the UK’s network of weather surveillance radars, which scan the sky several times a day. By measuring how radar signals bounce off airborne objects and using dual-polarisation technology to tell insects apart from raindrops, the scientists were able to estimate the number of insects flying between 500 and 700 metres 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. Interestingly, 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 Christopher Halsall, Associate Professor of Animal Biology at the University of Leeds, talks about the value of collaborating with radar experts at the National Centre for Atmospheric Science: “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 the 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.”

The study highlights a clear trend that nocturnal insects, such as moths, are faring worse than their daytime counterparts. Artificial light at night, already known to disrupt insect behaviour, may be contributing to their decline. The researchers found that areas with more light pollution showed lower night-time insect activity.

“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,” says Dr Mansi Mungee.

Beyond insects, this innovative use of weather radar could transform how we monitor airborne wildlife in general. The data is freely available and covers wide areas, making it a cost-effective, scaleable, and standardised method for long-term ecological research and conservation.

As insect populations continue to shift in response to climate change, land use, and light pollution, this new radar approach offers hope – not just for better monitoring, but for better protection. For example, weather radar monitoring of insects could contribute to urban planning by revealing surprising insect hotspots in cities due to light attraction. 

“The importance of this study is to open 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,” says Dr Christopher Halsall.

The researchers are already working with Natural England and the Department for Environment, Food & Rural Affairs to inform strategies that aim to lessen insect declines: “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,” adds Dr Christopher Halsall.

The research team included scientists from Keele University, National Centre for Atmospheric Science, Rothamsted Research, UK Centre for Ecology and Hydrology, University of Leeds, and University of Reading. The work was made possible with funding from the Natural Environment Research Council. Dr Mansi Mungee led the work as a postdoctoral researcher at University of Leeds, and is now based at Azim Premji University, India.