Effects of roads on insects: a review

In the last few decades, mounting evidence points to a negative impact of roads on several groups of animals. Most studies on the effects of roads on animal populations concentrate on vertebrates, and only a few on insects. It is difficult to determine the real effects of roads on insects due to the variety of methods used. We review recent literature examining the ecological impact of roads on insects. The objectives of our synthesis are to gain insight into the effects of the construction and operation of a road on insect groups, and to determine the gaps of knowledge. We found that roads negatively affect the abundance and diversity of insects due to two main factors: (1) the high mortality of some groups when crossing the road, with more impact at higher traffic volumes. (2) The unwillingness of many species to cross a road or live close to it. Roads are major barriers for small or flightless species, although the response varied for flying species. Finally, both experimental and observational evidence support the idea that air pollutants and de-icing salt used for the road maintenance negatively affect insects.