Transportation infrastructure is a growing but under-appreciated threat to the world’s primates.
Written By Benjamin Galea
7th April 2022
The expansion of linear infrastructure development into primate territory: necessary or needlessly destructive?
Approximately 75% of the world’s 493 extant primate species occurring across their native ranges (Asia, mainland Africa, Madagascar, and the Neotropics) are currently experiencing considerable population declines. Primates serve key ecological functions such as seed dispersal and pollination, generate income or food for people, hold cultural significance, and yield invaluable insights into human evolution. Linear infrastructure, namely, roads, rail, electrical transmission lines, pipelines, seismic lines, and aerial tramways, collectively termed transportation and service (T&S) corridors, are recognised by the IUCN as significant contributors to the global decline of primates. There is currently an increased demand to expand T&S corridors in areas where a large proportion of primates occur and where governance and institutional regulations happen to be weak, further accelerating the decline in primate populations.
The global extent and significance of such impacts on primates remains to be formally assessed, and the most effective mitigation approaches required to address these impacts also need to be identified. We conducted the first comprehensive systematic review of the impact of T&S corridors on primates. The number and distribution of affected species, the types of T&S corridors affecting different species, the severity of impact, and species’ responses to such impacts were explored. We also sought to determine what mitigation measures have been recommended, implemented, and evaluated and which have been effective and why. We focused on gaps in knowledge relating to impacts and mitigation measures and taxonomic and geographical biases in current research.
Chimpanzees risk the crossing of an unpaved road in Uganda. Photo: Cheryl Ramalho
The impact of transportation and service corridors on primates
Out of 523 studies, 327 were identified as suitable and included in this review. The majority of studies were conducted in Asia (45%), followed by mainland Africa (31%), the Neotropics (22%), and Madagascar (2%). We found 218 primate species and subspecies (44% of total amount) across the globe that are currently affected by T&S corridors. This number is far higher than the 92 primate species (including 9 subspecies) listed by the IUCN as currently threatened by T&S corridors. Our review uncovered that roads were the corridor type with the greatest and most widespread impact on primates (Figure 1). Roads are rapidly expanding into areas that have until now been relatively road-free. The impacts from roads affected all primate families and at least one species from each genera.
Figure 1. The number of primate species impacted by each type of transportation and service corridor based on the reviewed literature
After roads, electrical transmission lines and pipelines posed the next-greatest threat to primates. Like roads, these corridors are strongly associated with deforestation in primate habitats because of their construction processes. Arboreal and semiterrestrial primates that would normally use tree branches to brachiate (i.e., swinging from branch to branch) or cross between canopies are at a risk of death by electrocution from exposed transmission lines. Pipelines associated with hydroelectric, gas, and oil projects severely fragment primate habitats. They also require the creation of additional access roads for construction and maintenance, potentially boosting other activities, such as logging and hunting. The impacts of pipelines are similar to those of seismic lines, resulting in typically extensive habitat loss and increased access for human activities. Railway tracks caused habitat loss and fragmentation in a manner similar to roads. However, despite presenting an extreme barrier to highly arboreal primates, they appear to be less of a barrier to semiterrestrial primates than roads and cause fewer collisions, potentially because of lower and more predictable rail traffic volume.
Mitigating the impacts on primates
Mitigating the impact of T&S corridors on biodiversity requires a number of approaches: taking measures before infrastructure is developed (halting or altering development plans), in situ interventions that avoid or reduce impacts directly on-site, educating users of T&S corridors once development is complete, and the restoration or offsetting of habitat disturbances. Interventions to reduce mortality and facilitate movement across gaps are diverse and must consider whether animals are preferentially terrestrial or arboreal. Wildlife crossing structures suspended between trees and other structures for arboreal animals have been used extensively with significant success. We found numerous wildlife crossing structures that effectively aid primate travel between fragments created by T&S corridors or activities that have been facilitated by T&S corridors. These structures can be of minimal cost to construct and maintain (Figure. 2).
Figure 2. The diversity of effective wildlife crossing possibilities for primates. Wildlife crossings with little or no evidence of use by primates include large bridges, underpasses and steel ropes.
Aside from crossings, traffic control measures and insulation of electrical transmission lines have been implemented to prevent primate collisions and electrocutions. Insulation is simple and effective enough, either using insulated lines and terminal bridges when building new transmission towers, upgrading existing ones that are exposed, or braiding multiple lines into one insulated line to reduce the risk of electrocution.
We recommend that apart from expanding research efforts, T&S corridors also be more strongly recognized by government and conservation bodies as a mounting threat to primates and other animals. A clear direction is needed for the management of T&S corridors already in place and the assessment of those being planned. Ideally, primates and other animal groups affected by T&S corridor developments are safeguarded before, during, and after development takes place. Regional governing and funding bodies should ensure that developers and users of T&S corridors are properly regulated, sanctioned, and made aware of the threat which they pose to primates, other biodiversity, and ecosystem integrity.
Author information:
Benjamin Galea
Contact: bengalea97@gmail.com
Source:
Galea, B., & Humle, T. (2021). Identifying and mitigating the impacts on primates of transportation and service corridors. Conservation Biology. 1–14. https://doi.org/10.1111/cobi.13836
Editor:
Fernanda Teixera and Rodney van der Ree
Cite this summary:
Galea, B. (2022). Transportation infrastructure is a growing but under-appreciated threat to the world’s primates. Edited by Teixera, F. and van der Ree, R. TransportEcology.info, Accessed at: https://transportecology.info/research/transportation-threats-to-primates [Date accessed].
