Chapter 4
Railways as Barriers for Wildlife:
Current Knowledge
Rafael Barrientos and Luís Borda-de-Água
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.
R. Barrientos (&) Á L. Borda-de-Água
CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos,
Universidade do Porto, Campus Agrário de Vairão, Rua Padre Armando Quintas,
4485-661 Vairão, Portugal
e-mail: barrientos@cibio.up.pt
R. Barrientos Á L. Borda-de-Água
CEABN/InBIO, Centro de Ecologia Aplicada “Professor Baeta Neves”, Instituto Superior de
Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
© The Author(s) 2017
L. Borda-de-Água et al. (eds.), Railway Ecology,
DOI 10.1007/978-3-319-57496-7_4
43
Railways as Barriers for Wildlife:
Current Knowledge
Rafael Barrientos and Luís Borda-de-Água
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.
R. Barrientos (&) Á L. Borda-de-Água
CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos,
Universidade do Porto, Campus Agrário de Vairão, Rua Padre Armando Quintas,
4485-661 Vairão, Portugal
e-mail: barrientos@cibio.up.pt
R. Barrientos Á L. Borda-de-Água
CEABN/InBIO, Centro de Ecologia Aplicada “Professor Baeta Neves”, Instituto Superior de
Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
© The Author(s) 2017
L. Borda-de-Água et al. (eds.), Railway Ecology,
DOI 10.1007/978-3-319-57496-7_4
43