Written by Pablo Medrano-Vizcaíno, Clara Grilo & Manuela González-Suárez

November 13th, 2023

Sloths are highly vulnerable to road impacts in Latin America. *Photo credit: Andrés Reinoso Morales*

Plans for future road and railway developments are ambitious across many parts of the planet, including highly biodiverse regions. In these areas, road mortality and other impacts affect a great number of wild species. However, the implementation of rigorous impact assessments and development of comprehensive avoidance, minimisation, and mitigation plans has been hindered by a lack of detailed research.

We developed a method to identify areas and species that should be prioritized for road ecology-focussed conservation and research. This approach can be applied to any region and to different taxonomic groups. Here, as a case study, we developed this work in Latin America, a highly biodiverse region where road and rail expansion is rapid and the impacts on many species of fauna and regions are unknown.

For this, we systematically searched for studies about wildlife roadkill in Latin America. We found 85 studies from which roadkill data was available for 346 bird species and 159 mammal species. From each found study, we collated the number of roadkill per species and various relevant variables, such as sampling period, length of the studied road, and geographical coordinates of the study area. Roadkill rates per species were calculated as the number of carcasses divided by the length of the road surveyed and the sampling period. This rate was multiplied by 365 to obtain standardized roadkill rates as the number of individuals per kilometre per year.

With this data, we predicted roadkill rates over a 1° × 1° grid cell across Latin America using machine learning Random Forest models (a fancy statistical method with a high predictive accuracy) that combined observed roadkill rates, study location, wildlife traits (morphological, life history, and diet data) and habitat preferences (top panel of Figure 1). Finally, the combination of predicted roadkill rates per species with road density, and location of studies, allowed us to identify priority areas for research and conservation in Latin America.

To identify priority species for conservation and research, we calculated:

the percentage of species reported as roadkill
the percentage of species classified as Threatened (Critically Endangered, Endangered, and Vulnerable), Data Deficient, and Not Threatened (Near Threatened and Least Concern) according to the IUCN Red List (https://www.iucnredlist.org/)
the average predicted roadkill rate for each taxonomic order.

Then, we classified as conservation priorities those orders with at least 33% of species reported as roadkill and high predicted roadkill rates. Additionally, we identified two types of research priorities:

Type A for understudied but likely susceptible orders (high predicted roadkill rates, and roadkill data available for <33% of species)
Type B for unstudied groups (no roadkill data available) with at least 33% of species listed as Threatened or Data Deficient (Figure 2).

Priority areas for conservation

We found that the Amazon, a region with a relatively low road density and many road-free areas is inhabited by many species which are highly vulnerable to road mortality. Upgrading or building new roads in this region would be devastating for wildlife – and all new road projects should be avoided here. We categorized this region as a priority for conservation. A similar situation was found for some areas of Argentina, Colombia, and Panama (bottom panel of Figure 1).

Priority taxa for research

We identified birds such as cuckoos, nightjars, pelicans and waterfowl, and mammals like rabbits and hares as priorities for research. Although these groups have a high vulnerability to roadkill, only a few species were detected on the road surveys (<33%). Additionally, birds like albatrosses and penguins, and mammals such as shrews, shrew opossums and moles also require research. According to the IUCN, a considerable percentage of species (at least 33%) from these groups are threatened with extinction or classified as Data Deficient (Figure 2). Although actual roadkill rates are still unknown (surely because of lack of studies), road mortality is likely a major threat to their populations and urgent investigation of the impact of roads is necessary.

Figure 2. Priority taxa for conservation and research. T=number of threatened species, DD=Number of species categorized as Data Deficient, NoT=Number of species not classified as T or DD, %=percentage of species reported as roadkill.

A widely applicable approach

The results presented in this study can guide the strategic allocation of resources for conservation and research in Latin America. Our method can also be applied to identify priorities for other regions and taxa in other parts the world. For example, it may be particularly valuable for countries and regions where resources for scientific studies are limited, such as in Africa and much of Asia. The method can also be used to inform preliminary impact assessments of proposed road and rail projects as an initial screening tool to identify at-risk species that may be impacted by the project and thus warrant further detailed investigation.

Author information

Pablo Medrano-Vizcaíno, Ecology and Evolutionary Biology, School of Biological Sciences, University of Reading, United Kingdom & Red Ecuatoriana para el Monitoreo de Fauna Atropellada-REMFA, Quito, Ecuador. Contact: pabmevi@gmail.com

Clara Grilo, Department of Biology, Faculty of Sciences of the University of Lisbon & Centre for Environmental and Marine Studies (CESAM), University of Aveiro, Portugal

Manuela González-Suárez, Ecology and Evolutionary Biology, School of Biological Sciences, University of Reading, United Kingdom

Source citation

Medrano-Vizcaíno, P., Grilo, C., & González-Suárez, M. (2023). Research and conservation priorities to protect wildlife from collisions with vehicles. Biological Conservation, 280, 109952. https://doi.org/10.1016/j.biocon.2023.109952

Editor:

Daniela Araya

Cite this summary:

Medrano-Vizcaíno, P., Grilo, C. & González-Suárez, M. (2023). Priority regions and species to study and protect from road impacts in Latin America. Edited by Araya, D. TransportEcology.info, Accessed at: https://transportecology.info/research/priority-regions-species-roads-latinamerica