Roadsides are wonderful. Over only a span of a few meters, the vegetation changes completely. A line-shaped ecosystems that differs in all imaginable conditions from the natural, undisturbed vegetation next to it.
Over the pace of only a few footsteps, you can find a completely altered microclimate, messed-up hydrology and a changed nutrient composition. Roadsides get often a lot more sun because they are less shaded by a plant canopy. Disturbance by cars and road building often provides a reasonable amount of bare soil. And that is very important: that exhausting competition for resources with other species is finely reduced!
Let this be exactly the kind of ecosystem loved by our aliens. This particular combination of factors results in a nice and clear correlation: where you have roadsides, you find aliens. Only a few meters away from the road, they disappear.
The extent of these road effects, although not always visible, can sometimes be felt even far away from the road. Even more important in our story, roadsides can become a source of alien species, releasing their aliens in the undisturbed nature away from the roads. If the aliens manage to escape from the roadsides – where their damage is limited to these few already ruined meters, they can become a real problem.
What happens with these roadsides and their associated aliens in the mountains is one of the main questions from my research. So I promise you to reveal more about this line-shaped ecosystems as soon as my paper is published.