Around 25 million kilometers of new roads are expected to be built worldwide by 2050. Along with power lines and railways, highways crisscross the landscape everywhere, disrupting ecosystems.
This linear infrastructure prevents animals from moving safely in their habitat. It also reduces access to the resources they need, such as food, enough space, and mating partners. This threat to biodiversity is a conservation issue globally, but especially in developing countries where 90% of new road construction is expected.
The African continent is home to unique biodiversity and extraordinary landscapes. Planned infrastructure developments will no doubt threaten some of the continent’s last pristine deserts.
We are particularly concerned about the future of primates. The International Union for Conservation of Nature (IUCN) lists half of the continent’s 107 primate species as threatened.
Primates are affected by roads
According to the IUCN, 18% of the world’s primates are directly affected by roads and railways and 3% by public service infrastructure. However, these numbers are based on limited research. The true impact is likely to be greater.
The case of South Africa shows why. None of the South African primate species currently have linear infrastructure listed as threatened by the IUCN. But that doesn’t mean they aren’t negatively affected. It just means that lists need to be better informed.
The more mortality data available, the better we will understand impacts, know where to focus interventions, and inform future infrastructure developments to lessen human impact on biodiversity.
We recommend that infrastructure, such as roads and power lines, be more prominently recognized as a direct threat when developing Red List assessments.
primate deaths
Most of the electrocution data used in our study was accessed from the Eskom Central Incident Register.
Roadkill data for our study were available from two sources: the Endangered Wildlife Trust’s Wildlife and Transport Program national database and our own observations.
Since 2011, the Endangered Wildlife Trust has received records of systematic patrols on certain roads and species, and investigative research from experts in specific areas. Citizen science data comes from across the country, including national and regional highways, with varying speed limits, widths, and vehicle usage.
systematic patrols
The area covered by systematic patrolling is 1,370 km, covering 0.2% of the country’s entire road network and 0.9% of the paved road network.
The highest number of deaths recorded were of vervet monkeys. This was to be expected as vervet monkeys have a much wider geographic distribution in South Africa than bushbaby and samango monkey species, so they are more likely to encounter roads and power lines.
The greater (or fat-tailed) bushbaby and samango monkey are associated with forests with woodlands covering only about 0.1% of South Africa’s land area.
While the total of 483 primate deaths over 25 years may not seem very high, we can assume that many remain undetected. For example, carcasses can be removed by scavengers or hidden by dense vegetation along roadsides. They may be in remote locations, in the case of power lines, or seriously injured animals may later die some distance from the road.
For highways, the actual fatality rate can be 12 to 16 times the detection rate.
Solutions to build more nature-friendly roads
Encouragingly, there are more and more to look for which show that primates, as well as many other tree-dwelling species, accept man-made canopy bridges as a means of crossing gaps in their habitat.
In South Africa, we conducted a field experiment to test what type of canopy bridge primates would use to cross gaps between trees. We found that all five South African primate species used the canopy bridges offered to them. His preferred design was a solid pole bridge rather than a stair bridge.
More and more roof bridges of various types are being provided in different countries. But the investigation shows that Africa is lagging behind other continents in doing this, and there are no canopy bridges in South Africa. We suggest that all infrastructure development projects pay attention to maintaining the integrity of landscapes, for example by providing bridges for animals.
Registration of animals killed on roads
We all need and use linear infrastructure in our daily lives, so we all have some level of responsibility. Therefore, we encourage people to record wildlife kills and submit them to publicly available repositories such as iNaturalist any Global Biodiversity Information Facility .
Laura Praill of Oxford Brookes University and her colleagues are also developing a new global database of roadkill primates and it should be available to the public in April 2023.
Public awareness and participation are essential to lessen the human impact on biodiversity.
This article was written by Birthe (Bibi) Linden, Postdoctoral Research Fellow at the University of Venda, and Wendy Collinson, Research Fellow and South African Research Chair in Biodiversity Value and Change at the University of Venda.