The study of the negative effects of roads on animals is still insufficient

The studies that analyse the effects of the negative impacts of roads on animal populations have focused, above all, on large mammals in developed countries, without taking into account other less striking species or developing countries, according to a research project undertaken by Universidad Complutense de Madrid (UCM).

The work, published in Perspectives in Ecology and Conservation, consisted of a bibliographic review of 1,517 studies taken from the Web of Science repository regarding three subjects: roadkill, the fragmentation of the habitat and measures to mitigate these two impacts.

Noteworthy among the conclusions is the lack of variety of species: the studies only consider 2% of species endangered by roads, according to the Red List of Threatened Species, compiled by the International Union for Conservation of Nature (IUCN) – the most complete list of the state of conservation of species of animals and plants on a global scale.

This percentage focuses on large mammals, primarily carnivores, such as foxes and bears (36 %), along with hoofed animals such as deer and antelope (15%), marsupials such as kangaroos and koalas (14%) and tortoises (13%).

The authors point to a lack of less striking species that are also affected by transportation networks, including primates, bats and invertebrates.

In terms of their location, biologists find the studies in Southeast Asia, South America and Central Africa to be insufficient.

This geographic and species limitation, while affecting decision-making on conservation matters does not reveal the reality of the global problem.

“This lack of knowledge should be covered in any future research. For example, instead of recording roadkill, we should study how this affects the population dynamic. When seeing whether roads hinder the movements of fauna and whether animals use the mitigation measures installed, studies should include whether the absence of connectivity or the improvement in this following mitigation affect the survival of populations that live close to transportation networks”, proposes Rafael Barrientos, a researcher at the  Department of Biodiversity, Ecology and Evolution at UCM.

In addition to the Madrid university, the Portuguese universities of Lisbon, Aveiro and Porto also took part in the study, along with the German Centre for Integrative Biodiversity Research and Martin Luther University Halle-Wittenberg.