About 100 Trillion Bugs: Weather Radar Reveals How Many Insects Fill U.S. Skies on a Typical Summer Day

For many Americans, a summer evening is defined by the steady hum of insects. But translating that familiar soundtrack into a national-scale estimate of aerial insect traffic requires a different tool: weather radar.

How Researchers Counted the Uncountable

Scientists from the Swiss Federal Research Institute, the University of Oklahoma and MIT developed a method that uses data from the network of operational weather radars maintained by NOAA to estimate flying-insect abundance across the continental United States. By analyzing observations from 140 NOAA radars, they converted radar echoes from biological targets into an estimate of insect numbers and biomass.

Headline Finding

The team estimates that roughly 100 trillion flying insects traverse the lower 48 states on a typical summer day. That enormous cohort represents millions of tons of biomass that help sustain birds and other insectivores.

What The Decade-Long Record Shows

The researchers compiled a continuous time series of flying-insect abundance spanning 2012–2021 and found that, at the continental scale, overall abundance was relatively stable during this period. However, this apparent balance masks important regional differences.

Regional Patterns And Temperature Links

Winged-insect density rose in some regions and declined in others. Those regional trends correlated with winter temperature changes: areas that warmed experienced declines in flying-insect density, while areas that cooled tended to see increases. The effect of winter warming was stronger at higher latitudes. The authors suggest that warmer winters may disrupt cold-induced dormancy strategies that many insects rely on to survive lean months.

Strengths And Limitations Of The Radar Approach

Radar offers a powerful way to monitor insect abundance over vast areas and long timeframes—something that local traps or visual surveys alone cannot provide. However, radar cannot identify species or life stages, so it cannot replace ground-based surveys. The researchers emphasize the value of combining radar records with local monitoring, citizen science and targeted sampling to obtain species-level and ecological detail.

“It is therefore important to combine radar data with other data sources—local surveys, citizen science, and so on,” said Elske Tielens of the Swiss Federal Research Institute.

Context And Future Use

The study authors note that steep insect declines may have occurred prior to the era covered by NOAA radar records—likely before the 1990s—so the radar baseline primarily reflects trends since instrumented monitoring became widespread. Going forward, the radar-based method provides a reproducible baseline for detecting future changes in flying insects and can be applied in other regions of the world where ground monitoring is sparse.

Bottom line: Weather radars reveal that an astonishing number of insects fill U.S. skies on a summer day, and this large-scale view—paired with on-the-ground monitoring—can help scientists track changes in insect abundance and behavior as climate and land use continue to change.

Study published in Global Change Biology. Lead image credit: Tunatura / Shutterstock. Originally reported by Nautilus.