Roads act act corridors, to the benefit of humans and the sometimes benefit of plants and animals. They help move people around, but they also fragment landscapes. They provide paths for native species to expand, but also allow non-native species to get a foothold. They cause great disturbance in the landscape, which is helpful if you’re a disturbance-dependent species, but otherwise not so great.
Roads in the mountains can act as corridors to help species move both up and down the elevational gradient. Given that climate change is likely to cause range shifts that move upward in elevation, mountain roads may have unintended consequences in the future for some species’ distribution. A new study has focused on looking how species ranges are altered along roads that span an elevational gradient as compared to the surrounding natural habitat, focusing on plants. It also asks whether there is a difference between native and non-native species in their use of mountain roads as corridors.
Using vegetation surveys from eight mountain regions across four continents (MIREN, the Mountain Invasion Research Network), researchers collected data on hundreds of species and compared their native status, elevational range, and affinity for abiotic factors (temperature and nitrogen). They found that the elevational range amplitudes of non-native plants were on average broader in the roadsides than in the adjacent vegetation, likely due to the increased disturbance that helps spread propagules and the higher nutrient levels found in roadsides. Native plants also had broader range amplitudes in roadsides as compared to adjacent vegetation, although the effect was not as pronounced. Overall, roads were effective corridors for all species regardless of native status, and aided both low-elevation plants in moving upward, and high-elevation plants in moving downward.
So what does this mean for mountain plants facing climate change? While roads may be detrimental in fragmenting the landscape and supporting the movement of non-native species, they may also act as a much-needed lifeline for native species to expand their range. Roads will be a more important factor than previously realized when predicting how species distributions will shift within mountainous regions.
Lembrechts, J. J., J. M. Alexander, L. A. Cavieres, S. Haider, J. Lenoir, C. Kueffer, K. McDougall, B. J. Naylor, M. A. Nuñez, A. Pauchard, L. J. Rew, I. Nijs, and A. Milbau. 2016. Mountain roads shift native and non-native plant species’ ranges. Ecography. DOI: 10.1111/ecog.02200.
Haddad, N. 2015. Corridors for people, corridors for nature. Science 350: 1166-1167.