Is road traffic an important driver of global insect decline?

Insect populations have declined dramatically over recent decades, yet the relative importance of the underlying drivers remains poorly understood. These declines are commonly attributed to habitat loss, climate change, agricultural intensification, and pesticide use. However, we hypothesize that road traffic represents an additional, largely overlooked driver of insect decline. Local research shows that road traffic contributes to insect mortality not only through direct collisions with vehicles but also via traffic-related pollutants and habitat disturbance. Roads and vehicles are now pervasive across landscapes worldwide, and traffic volumes have increased considerably over the past half-century. Despite this, the ecological consequences of road traffic for insects have received surprisingly little attention compared to other anthropogenic pressures.

To address this gap, we conducted a global analysis of the potential impact of road traffic on insect populations. Our spatial assessment reveals that agricultural and peri-urban landscapes—areas already identified as hotspots for insect declines—are disproportionately affected by high traffic densities.

Although a few studies have estimated insect mortality along specific road segments, little is known about the cumulative impact at regional or global scales. We extrapolate such local mortality estimates using global traffic data to approximate the worldwide impact of road traffic on insects. Our preliminary results indicate very high impacts of road traffic on insects. These findings underscore the urgent need to integrate road ecology into insect conservation frameworks and to develop mitigation strategies that address this overlooked threat.

However, mitigating the impact of road traffic on insects poses significant challenges. Roads and traffic may act as magnets for insects due to night-time lighting from streetlamps and vehicles, increasing collision risk. Traffic flows are constant throughout the year and extremely difficult to reduce without major societal changes. Moreover, road traffic introduces numerous additional stressors—such as chemical pollutants, noise, and microclimatic alterations—that compound its ecological footprint. We discuss these complexities alongside potential solutions, such as infrastructure design and lighting management, aiming to reduce the ecological impact of roads and safeguard insect biodiversity.