Image Credit: "Adelaide. Brownhill Creek. Two butterflies consorting in the middle of the road came to a sticky end." by denisbin is licensed under CC BY-ND 2.0.
May 11, 2023
Among the aspects studied about the impacts of roads on insects are those generated in construction, collisions and the barrier effect.
Construction of the work
From the earliest stages, soil removal kills many organisms that live within the soil and destroys ant nests. This is the most immediate impact, since the construction of the highway represents the destruction of the habitat of the insect species that inhabit these places.
Collisions with vehicles
In addition to being run over by insects with vehicles, this impact is amplified by the effects that light, noise and vibration from cars generate on these organisms, since, for example, some flying insects can be attracted to light, causing make the impacts more lethal.
Most of the studies focus on relatively large insects, in which some authors mention that road kill could affect the population dynamics. However, other researchers indicate that vehicle collisions are negligible compared to deaths from natural causes. For this reason, it is necessary to assess the long-term impacts of roads.
There is also a relationship between insect mortality and traffic volume, which, in turn, is usually linked to the size of the road. Thus, higher mortality has been found at intermediate levels of traffic and it has been proposed that, with high speed limits, insect mortality could be reduced due to the gusts of wind generated by automobiles, thus avoiding collisions.
In addition, the impacts also depend on the same characteristics of the insects, such as their size, behavior and sex. The different species of insects differ in many aspects, one of them is their mobility, since there are species that fly very short distances, which makes them less likely to cross a road than species that travel longer distances. Likewise, the impact will depend on how each species reacts to the microclimate created by the road.
The effect of roads as barriers to dispersal
In order to analyze the effect that the fragmentation of the landscape due to roads has on insects, studies of diversity and abundance have been carried out depending on the proximity to the road and, in some studies, it is observed that either diversity or abundance increases with the distance On the other hand, other works mention that the diversity of species is greater close to the highway, although the composition is very different from that which exists within undisturbed habitats.
The most notable aspect of the barrier effect is the fact that the insects avoid crossing the road, which usually causes them to move along the banks looking for a suitable place to cross, forcing them to travel long distances and move away from their habitat. Again, the width of the road and the volume of traffic may limit the crossing of insect species.
Muñoz, P.T., Torres, F.P. & Megías, A.G. Effects of roads on insects: a review. Biodivers Conserv 24, 659–682 (2015). https://doi.org/10.1007/s10531-014-0831-2