Night-flying insects over UK in decline, weather radar study reveals | Insects

Scientists used Met Office radar data to track trillions of insects flying over the UK for the first time and revealed an alarming decline in nocturnal species.

The team reused data from the UK network of 15 weather surveillance radars that scan the sky hundreds of times a day.

The analysis shows that daytime insect numbers remained relatively stable or even increased in southern regions between 2014 and 2021, but nighttime airborne insects decreased overall, especially in the far north.

Dr., who conducted the study as a postdoctoral researcher at the University of Leeds and currently works at Azim Premji University in India. “This is one of the first studies to show how day- and night-flying insects are affected differently and how their habitats influence these patterns,” said Mansi Mungee. “This is a very important step towards understanding where to focus conservation efforts.”

Modern radar works by sending microwave pulses that bounce off precipitation and other airborne obstructions. Radar can determine the location, number and size of airborne insects by measuring the return time, intensity and other characteristics of the signal.

The results show that an average of 11.2 tons of insects flew between 500 and 700 meters above the ground during daylight hours, and at night this number was just over 5 tons. Insect abundance was higher in areas with woodlands, grasslands, and even urban areas; however, it decreased in areas with intensive agriculture and high levels of artificial lighting.

Birds, bats and insects were first detected as mysterious spots under British military surveillance during World War II; Radar operators were so confused that the confusing signals were initially known as “angels”.

In the intervening decades, as radars have become preferred for weather forecasting, Met Office scientists have developed complex algorithms to eliminate “biological scatter” caused by swarms of insects and migratory birds.

Animal biology researcher at the University of Leeds and co-author of the study, Dr. “They were throwing away masses of data on biodiversity,” Christopher Hassall said. “We realized that this data could potentially be mined and that, rather than being intrusive, it could be a wealth of information.”

Instead, the insect mapping team ignored the other half of the data—rain, clouds, and weather—to reveal the insects’ aerial movements.

“Some of the insects are active fliers, some just follow thermals,” said Dr Ryan Neely, from the National Center for Atmospheric Science and the University of Leeds. “It’s a great way to visualize what the weather is doing. It’s really beautiful.”

The current study focused on overall numbers rather than how many different species are present; this is often the focus of citizen science monitoring of insect biodiversity.

Nocturnal insects such as moths have shown an overall decline over the past four years, driven by declines in northern regions. Scientists concluded that artificial light at night, which is known to disrupt insect behavior, may be contributing to their decline.

“It may be a disruption, but there’s also a change in the way we light the night in terms of the types of bulbs and car headlights being brighter,” Hassall said.

During both day and night, there was a decrease in species in the north and an increase in insects in the south; This is probably linked to the climate crisis.

“The numbers of northern species will decline because the weather is getting too hot and too dry for them,” Hassall said. “They will be replaced by southern species, but there is a delay.”

It turns out that cities have higher insect numbers than homogeneous farmland, which is likely to offer less diverse habitats. The findings were published in the journal Global Change Biology.