Tracking the skies: What 90 years of data reveal about high-flying insects and growing pest threats

Are insects really disappearing everywhere? A new international study published in Insect Science offers a more complex picture. While many ground-dwelling insects have declined sharply in recent decades, high-flying migratory insects that travel hundreds of meters above the ground seem to be holding steady.

These insects, including pollinators, predators, and crop pests, play a vital role in moving nutrients, energy, and genetic material across ecosystems. Studying them has proven notoriously difficult, as they spend much of their lives high in the atmosphere.

To fill this gap, researchers from Nanjing Agricultural University and international collaborators compiled a unique dataset spanning 92 years (1926–2017) across Europe, North America, and Asia. Using data from aerial sampling programs that employed kites, balloons, and aircraft alongside new fieldwork, they tracked long-term trends in high-altitude insect populations.

The results reveal a striking contrast to the widely discussed “insect apocalypse.” Overall, the abundance of migratory insects has remained largely stable over nine decades, suggesting that traits such as high mobility, rapid reproduction, and adaptability may protect them from some environmental pressures that have impacted non-migrant species.

However, the researchers also uncovered a more concerning shift: agricultural pests are on the rise. In regions such as East Asia and the UK, pest species like the rice leaf roller moth (Cnaphalocrocis medinalis) and the brown planthopper (Nilaparvata lugens) have increased sharply, while beneficial insects may be declining, a change that is masked by the overall stability in total numbers.

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Professor Gao Hu, corresponding author, explained:
"Our research, even when based on historically discontinuous data, clearly shows that the aerial abundance of major migratory pests has not declined over time. This challenges the assumption that pest pressures are naturally easing and underscores the urgent need to maintain and even strengthen our national long-term monitoring systems and pest management strategies. We cannot afford complacency; these ‘pests on the wing’ continue to pose a persistent threat to food security."

Professor Jason W. Chapman, co-lead author, added:
“Our work, which draws together decades of challenging high-altitude sampling, reveals an important truth: while much of our attention focuses on pests, the sky is also a vast highway for countless insect species, including vital predators and pollinators. The continued robustness of pest populations suggests that the entire high-altitude ecosystem remains remarkably active.

This points to a major knowledge gap, we are likely underestimating the scale and ecological importance of beneficial insect migration. To truly understand the health of our agricultural and natural systems, we must broaden our focus beyond the ‘villains’ to include the full airborne community.”

Dr Boya Gao, first author, noted:
“The absence of decline in these pest populations, even in fragmented historical records, likely reflects their extraordinary adaptability. High-altitude migration is a high-risk, high-reward strategy, and these insects have evolved remarkable resilience using favourable winds to travel vast distances and colonise new habitats. Their persistent numbers are a testament to this evolutionary success and must be factored into future pest management strategies.”

The team emphasizes the need for continued, high-altitude insect monitoring to distinguish between harmful and beneficial species. Tracking the insects flying above us and how their numbers are changing will be essential for protecting pollinators, supporting sustainable farming, and managing the growing challenge of crop pests in a changing climate.

About the Authors:
This study was conducted by a multinational research team co-led by Professor Gao Hu and Professor Jason W. Chapman. The group specialises in insect migration ecology, focusing on the movement patterns and population dynamics of major agricultural pests in East Asia. The first author, Dr Boya Gao, focuses on radar entomology and the study of high-altitude insect migration.

The team includes key collaborators from the Henan Academy of Agricultural Sciences, the Plant Protection Station of Xiushan (Chongqing), Rothamsted Research, the Natural Resources Institute (University of Greenwich), and the Centre for Ecology and Conservation (University of Exeter), who contributed invaluable data and writing support.

Together, this collaboration advances understanding of the large-scale ecological impacts of insect migration and its implications for food security and biodiversity in the face of global environmental change.

Read the full article here: https://onlinelibrary.wiley.com/doi/10.1111/1744-7917.70193