Green roads and highways to protect biodiversity: monitoring the impacts of the N4 national highway (TRAC N4), South Africa, on wildlife.

Abstract

Transport infrastructure, in this instance, roads and highways, is a critical element of sustainable human economic development and society by driving development and serving as the main mode of transport. In South Africa, road corridors are especially important in improving access from rural areas into areas of economic zones, which promotes development, job creation, and accessibility needs. In addition, road transport provides an enabling environment for freight movement and contributes ~74% of total land freight income in the sector in South Africa. However, when roads are not built following the bounds of sustainability, they may have negative impacts on both humans and the environment. Poorly planned transport infrastructure can have severe impacts on ecological connectivity and species survival. Roads can create barriers to wildlife movement, limiting terrestrial wildlife's ability to find essential ecological resources such as water, food, and mates. Road fragmented landscapes may accelerate incidents of wildlife-vehicle collisions. Whilst these incidents almost always result in wildlife mortality, they can also impact the overall health and functionality of ecosystems. Furthermore, they could risk human safety by causing injuries to road users. These impacts are particularly relevant in South Africa, which is home to iconic wildlife, with a wide array of habitats that harbour over 20,000 different species of flora and fauna, whilst still transitioning to a green economy. The present study expands on previous research by emphasising the urgent need for adopting road development projects that optimise social and economic benefits while safeguarding biodiversity and ecosystems through the inclusion of ecological connectivity. Firstly, the global use of camera trapping techniques as a research tool for monitoring crossing-structure use by wildlife in road fragmented landscapes was evaluated. Whilst the global trend in road ecology studies that deployed camera traps to evaluate crossing structure use has showed a geographical bias, it was clear that camera trap use to monitor wildlife crossing structures is still an emerging area of research. In addition, although the evaluation showed that the camera trap approach was successful in monitoring animals’ use of crossing structures, the study design, sampling, and surveying techniques deployed by each study varied considerably and were not standardised. This highlighted the need and significance of studies to maintain consistency in the protocol of monitoring crossing structure so that studies will be comparable in terms of use patterns. Secondly, green transport infrastructure has become an important element of sustainable development frameworks. Maintaining ecological connectivity between road-fragmented natural landscapes plays a significant role in conserving wildlife populations. The present study has comprehensively assessed the relevance of South Africa’s national policies on sustainable road transport development in maximising the ecological functionality of road networks through promoting the inclusion of ecological connectivity. This thesis further proposed a synthesised analytical framework for promoting transport infrastructure sustainability that presents a usercentric integrated model and establishes road project planning and design that optimise social and economic benefits while minimising negative ecological impacts through strategic collaborations. Thirdly, this study has explored wildlife roadkill patterns and animal movement on a national highway that bisects landscapes of grasslands, freshwater ecosystems and wetlands, which are suitable homes for a variety of species. This doctoral study further researched the usefulness of road specialised structures (bridges, culverts, viaducts and tunnels) in helping animals to move across the TRAC N4 Toll Route, so we can reduce roadkill incidents and improve landscape ecological functionality. This will assist in promoting the consideration and inclusion of ecological connectivity and biodiversity needs in road transport development sustainability frameworks in South Africa.