Railways as Barriers for Wildlife: Current Knowledge

Abstract

In this chapter we provide practical suggestions, together with examples, to identify, monitor and mitigate railway barrier effects on wildlife, as this is considered one of the railways' greatest impacts. Railways can be both physical and behavioral barriers to wildlife movement, as well as disturbance to populations living close to them. Also, mortality is recognized as an important contribution to the barrier effect. However, the consequences of habitat loss, and fragmentation due to railways alone remain largely unexplored. Barrier effects have mainly been mitigated with wildlife passes, with the effectiveness of this tool being one of the most-studied topics in Railway Ecology. Methods formerly employed to monitor pass usage, such as track beds or video-surveillance, are now being replaced by molecular ones. Among the latter methods, genetic fingerprinting allows individual-based approaches, opening the door to population-scale studies. In fact, genetic sampling allows for the assessment of functional connectivity, which is closely linked to successful reproduction and population viability, variables not necessarily coupled with crossing rates. There is strong evidence that railway verges offer new habitats for generalist species and for opportunistic individuals, a point that deserves to be experimentally explored in order to find wildlife-friendly policies. Preventing animals from crossing (e.g., by fencing), should be reserved for collision hotspots, as it increases barrier effects. Instead, it has been shown that warning signals or pole barriers effectively reduce collisions without increasing barrier effects. In this respect, we argue that computer simulations are a promising field to investigate potential impact scenarios. Finally, we present a protocol to guide planners and managers when assessing barrier effects, with emphasis on monitoring and mitigation strategies.

Methods to reduce wildlife collisions with rail vehicles

“…The growing railway infrastructure, the development of transport corridors and increasing speeds of vehicles cause the increase in impact of railways on the natural environment. Apart from the emission of exhaust gases into the atmosphere, among the effects of this long-term impact it can be noticed the fragmentation of habitats and disturbance of the balance of ecosystems as well as an increase in animal mortality as a result of the collision with the train [5]. This is undesirable both ecologically and for the reasons of traffic safety.…”

“…Rozbudowująca się infrastruktura kolejowa, rozwój korytarzy transportowych i coraz większe prędkości poruszania się pojazdów powodują zwiększenie oddziaływania kolei na środowisko naturalne. Poza emisją spalin do atmosfery, wśród skutków tego długofalowego oddziaływania można zauważyć fragmentacje siedlisk i zaburzenie równowagi ekosystemów oraz wzrost śmiertelności zwierząt w wyniku kolizji z pociągiem [5,6]. Jest to niepożądane zarówno ekologicznie, jak i ze względów bezpieczeństwa ruchu.…”

Identifying and mitigating the impacts on primates of transportation and service corridors

“…The impact of T&S corridors on different taxa is relatively well documented (e.g., van der Ree et al, 2011;Barrientos & Borda-de-Água, 2017;Richardson et al, 2017). The cause of wildlife population declines as a result of T&S corridors range from direct mortality to behavioral changes (e.g., Shannon et al, 2014;Sadleir & Linklater, 2016).…”

Spatial Response to Linear Infrastructures by the Endangered Golden Lion Tamarin

“…The second factor, which is known as the "barrier effect", refers to the combination of a series of factors, including mortality [16], that hinder animal movement over these structures. Animals may change their behavior to avoid clearings caused by habitat loss [17,18], the presence of physical structures, cars or traffic on roads [6,19], noise and vibration of railroads [20], or other disturbances…”