Status of Road Ecology Research in Africa: Do We Understand the Impacts of Roads, and How to Successfully Mitigate Them?

Abstract

Across Africa, transport infrastructure, including roads, is being built in over 30 planned development corridors that are likely to have major impacts on remaining natural habitats and associated biodiversity. Linked to this is the projected increase in human population size, which is predicted to grow by 1.3 billion people by 2050. Road ecology is the study of the ecological effects (both positive and negative) of roads and traffic but is perceived to be under-researched in Africa. In this context, we undertook a systematic review of road ecology research in Africa to understand the geographic and taxonomic scope of work undertaken to date, as well as recommendations for reducing the impacts of roads. We discovered 210 road ecology publications from Africa (published between 1954 and 2016), with most publications from the more affluent and politically stable regions (e.g., southern and East Africa). We found more publications than expected, with relevant research concealed within studies whose primary focus was on other topics. Most publications (1) focused on single species, and in particular on mammals (where chimpanzees and forest elephants were most studied); (2) were from southern Africa; and 3) were conducted in the grassland and savannah biome and the tropical and subtropical forest biome. Most publications examined the direct impacts of roads, in particular wildlife-vehicle collisions. Only one-third of the publications provided some form of recommendation for intervention to reduce or mitigate the impacts of roads, based on evidence from the publication. Most recommended interventions related to ecosystem or natural process recreation, as well as site and area stewardship. Gaps and future directions for research include rigorous testing of measures to mitigate the impacts of roads, inclusion of traffic monitoring in studies, understanding the impacts of upgrading roads, and exploring livelihood, economic and moral incentives and education and training as potential interventions for reducing the impacts of roads. Our review has highlighted the need for accelerating the study of the impacts of roads on natural habitats and biodiversity, in light of planned large-scale infrastructure development, and especially the study of appropriate mitigation measures that can be rigorously assessed and implemented before and during construction and upgrading of roads in Africa.

Mitigating the Impacts of Development Corridors on Biodiversity: A Global Review

“…There was only one specifically looking at cumulative impacts (Lechner et al, 2017). These findings align with Collinson et al (2019) who, in a review on road ecology research in Africa, found that most publications examined the direct impacts of roads only and focused on single species assessments. Notably, there were only two publications specifically assessing the impacts of development corridors on ecological connectivity (Heinicke et al, 2019;Wierzchowski et al, 2019), despite that habitat fragmentation is one of the most well-established effects of infrastructure development (van der Ree et al, 2011;Barrientos et al, 2019), which often occurs in early stages of corridor construction.…”

“…Although the term "Development corridor" has been often used as an umbrella term for these initiatives (Mulenga, 2013;Laurance et al, 2017;Enns, 2018;Collinson et al, 2019;Dong et al, 2019;Heinicke et al, 2019;Sloan et al, 2019b;Müller-Mahn, 2020), corridor terminology is diverse, not standardised, and it depends on the purpose of the corridor, the actors involved, and the stage at which it is. As such there are transport, trade, utility, agricultural, or resource corridors, among others (Nogales, 2014;Hope and Cox, 2015;The Development Coridors Partnership, 2021).…”

“…Here, we describe corridors from a biodiversity perspective and identify the elements of best practice in biodiversity impact mitigation, considering related ecosystem services where possible. We focus on the specific nature of these complex initiatives acknowledging that the science to understand and manage the impacts of individual infrastructure projects has many years of history (Spellerberg and Morrison, 1998) and is well-advanced, especially for roads (Coffin, 2007;Fahrig and Rytwinski, 2009;van der Ree et al, 2011;Forman et al, 2015;Bennett, 2017;Collinson et al, 2019) but also railways (Barrientos et al, 2017(Barrientos et al, , 2019. Here we are particularly interested in development corridors more broadly and how impacts on biodiversity are assessed and what mitigation measures (if any) are proposed.…”

“…How Biodiversity Impact Mitigation Is Approached Collinson et al (2019) also found that only one-third of publications on impacts of roads on biodiversity provided recommendations for interventions to reduce or mitigate the impacts. Comparatively, in this review, only one-fifth (52 out of 271) of publications that assessed impacts on biodiversity discussed mitigation measures; meaning that most publications assessing impacts of corridors on biodiversity do not propose recommendations to manage the impacts they foresee.…”

Inference in road ecology research: what we know versus what we think we know

“…[4][5][6]). It is then very natural that researchers recommend mitigation measures based on their results in the Discussions of their papers [7]. These recommended measures generally fall into one of three major categories: measures intended to increase animal movement across roads, measures to reduce road-kill and measures to reduce traffic effects on roadside populations, such as pollution and traffic disturbances [8].…”