More study needed on the negative effects of roads on wildlife at the population level
Written By Rafael Barrientos, Fernando Ascensão, Marcello D’Amico, Clara Grilo and Henrique M. Pereira
25th October 2022
A global road network is growing rapidly and associated with increased economic development. This growth typically comes at a high cost to biodiversity, with several well-documented negative impacts on wildlife species. Roads can accelerate economic growth and social integration, facilitating the transportation of people and goods, but they are also responsible for impacts such as animal mortality, obstructing movement, habitat loss and fragmentation, as well as indirect impacts including forest removal, increased human access and illegal hunting of wildlife.
Current research biases
We reviewed studies on the impacts of roads (roadkill, fragmentation and the mitigation actions addressed for both impacts) from around the world using the ISI Web of Science database. We identified 898 studies on mortality, 775 on habitat loss and fragmentation and 589 on mitigation, totalling 1517 different studies (as some of them studied more than one topic). When we focused on studies on road effects at the population level, e.g., how road mortality affects population viability or genetic structuring by reducing connectivity, we found only a small proportion addressed the population scale. Namely, only 7% of studies on mortality, 12% on habitat loss and fragmentation and 3% on mitigation (n= 117 studies), employed population-oriented approaches. Most population-level studies focused on the effects of habitat loss and fragmentation (80%), followed by roadkill (55%), and mitigation actions (16%).
These studies were mainly on carnivores (36%), ungulates (15%), marsupials (14%) and turtles (13%), whereas studies on invertebrates were anecdotal. Most (90%) of population-level studies were conducted in developed countries like the USA, Canada or Australia, whereas biodiversity-rich regions of Southeast Asia, South America or Central Africa had few studies. Concerningly, only 2% of the species identified by the IUCN Red List as threatened (Critically Endangered, Endangered or Vulnerable) by roads were included in the studies. This suggests that the scientific literature covers a minority of the species affected by the incoming expansion of the global infrastructure network.
Rethinking the focus of road studies
Our results show that we are far from understanding how roads affect the long-term viability of wildlife populations. Addressing this challenge will require shifting our focus from short-term studies to long-term studies, and rather than studying specific road sections or species we should be focusing on the road network and communities. One objective should be to obtain empirical data to carry out solid analyses to evaluate the extent to which the long-term persistence of the populations living in the vicinity of roads is affected by them. We highlight some key studies in our review that have addressed this global conservation concern with population-oriented approaches, demonstrating that this paradigm shift is possible. However, the fact that most population-level studies have been carried out on iconic species (but not always threatened) and in high-income countries shows that higher-quality studies will be required in developing nations with areas of high biodiversity.
Cover Photo: Tim Tetzlaff
Author information:
Rafael Barrientos, Road Ecology Lab, Department of Biodiversity, Ecology and Evolution, Faculty of Biology, Complutense University of Madrid, José Antonio Novais, 12, E-28040, Madrid, Spain. Contact: rbarrientos@ucm.es
Fernando Ascensão, cE3c - Centre for Ecology, Evolution and Environmental Change, Faculdade de Ciências, Universidade de Lisboa, 1749-016, Lisboa, Portugal
Marcello D’Amico, THEOECO, CIBIO-InBIO, University of Porto and University of Lisbon, Tapada da Ajuda Campus, 1349-017, Lisbon, Portugal
Clara Grilo, Department of Biology, Faculty of Sciences of the University of Lisbon & Centre for Environmental and Marine Studies (CESAM), University of Aveiro, Portugal
Henrique M. Pereira, German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig Deutscher Platz 5e, 04103 Leipzig, Germany & Institute of Biology, Martin Luther University Halle-Wittenberg, Am Kirchtor 1, 06108 Halle (Saale), Germany
Source:
Rafael Barrientos, Fernando Ascensão, Marcello, D’Amico, Clara Grilo, Henrique M. Pereira (2021) The lost road: Do transportation networks imperil wildlife population persistence? Perspectives in Ecology and Conservation 19: 411-416. DOI: 10.1016/j.pecon.2021.07.004.
Editor:
Tony Clevenger
Cite this summary:
Barrientos, R., Ascensão, F., D’Amico, M., Grilo, C. & Pereira, H.M. (2022). More study needed on the negative effects of roads on wildlife at the population level. Edited by Clevenger, T. TransportEcology.info, Accessed at: https://transportecology.info/research/road-impacts-population-studies [Date accessed].