(Kalarus and Bąkowski 2015). The wide range of environmental conditions
occurring in tracks, led to the presence of a large number of nectar plant species,
allowing the existence of many butterfly species, from those selecting dry and warm
microhabitats to forest specialists (Kalarus and Bąkowski 2015). Similar results
have been found for other pollinators due to the high diversity of bee forage flora,
although their diversity is higher in lines with intermediate traffic volume, and
differs between microhabitats within the embankments (Wrzesień et al. 2016). On
the contrary, Cerboncini et al. (2016) found no effects of railway edge on microclimate in a Brazilian Atlantic forest, probably because railway track was narrow
and the forest was well developed. Finally, especially in more impacted landscapes,
there is an opportunity to integrate old tracks once they are abandoned into the
regional conservation schema. They can act, for instance, as habitat corridors
among protected areas, as many of their new uses—like rail-cycle or hiking—are
wildlife-friendly activities. However, much more research is needed on the conservation potential of abandoned tracks as well as on cost-effective maintenance
methods, like the weeding by domestic animals used in France (Orthlieb 2016).
Also in France, Kerbiriou et al. (2015) found a strong increase in the population of
hibernating pipistrelle bats (Pipistrellus pipistrellus) in a railway tunnel as a result
of the end of the exploitation of the railway line, remarking on the idea that
abandoned railway structures can have second-life fulfilling conservation purposes.
Methods to Estimate Barrier Effects
Some of the methods we describe below were first used in road ecology studies (Smith
and van der Ree 2015), but all of them are useful for railway ecology studies as well.
Direct Methods
(1) Wildlife-train collisions data. This is the simplest method to estimate barrier
effects due to wildlife mortality. A reduction of WTCs after applying mitigation
measures has been commonly argued to be a measure of the effectiveness of
management policies (e.g., Andreassen et al. 2005; Kušta et al. 2015), although
WTC data without PVAs may be a poor surrogate of the impact of the railway.
(2) Track beds. These consist of a layer of fine sand, marble dust, or clay powder of 3–
30 mm thick, spread across the entire pass (usually underpass or culvert), and
smoothed with a brush. It should be fine enough to detect the tracks of small
vertebrates such as mice or amphibians, or even macroinvertebrates. The pass
must be reviewed every 1–2 days and, if necessary, the material must be removed
and extra material added (Yanes et al. 1995; Rodríguez et al. 1996; Baofa et al.
2006). This method, combined with strips of soot-coated paper, as well as
4 Railways as Barriers for Wildlife: Current Knowledge
49
occurring in tracks, led to the presence of a large number of nectar plant species,
allowing the existence of many butterfly species, from those selecting dry and warm
microhabitats to forest specialists (Kalarus and Bąkowski 2015). Similar results
have been found for other pollinators due to the high diversity of bee forage flora,
although their diversity is higher in lines with intermediate traffic volume, and
differs between microhabitats within the embankments (Wrzesień et al. 2016). On
the contrary, Cerboncini et al. (2016) found no effects of railway edge on microclimate in a Brazilian Atlantic forest, probably because railway track was narrow
and the forest was well developed. Finally, especially in more impacted landscapes,
there is an opportunity to integrate old tracks once they are abandoned into the
regional conservation schema. They can act, for instance, as habitat corridors
among protected areas, as many of their new uses—like rail-cycle or hiking—are
wildlife-friendly activities. However, much more research is needed on the conservation potential of abandoned tracks as well as on cost-effective maintenance
methods, like the weeding by domestic animals used in France (Orthlieb 2016).
Also in France, Kerbiriou et al. (2015) found a strong increase in the population of
hibernating pipistrelle bats (Pipistrellus pipistrellus) in a railway tunnel as a result
of the end of the exploitation of the railway line, remarking on the idea that
abandoned railway structures can have second-life fulfilling conservation purposes.
Methods to Estimate Barrier Effects
Some of the methods we describe below were first used in road ecology studies (Smith
and van der Ree 2015), but all of them are useful for railway ecology studies as well.
Direct Methods
(1) Wildlife-train collisions data. This is the simplest method to estimate barrier
effects due to wildlife mortality. A reduction of WTCs after applying mitigation
measures has been commonly argued to be a measure of the effectiveness of
management policies (e.g., Andreassen et al. 2005; Kušta et al. 2015), although
WTC data without PVAs may be a poor surrogate of the impact of the railway.
(2) Track beds. These consist of a layer of fine sand, marble dust, or clay powder of 3–
30 mm thick, spread across the entire pass (usually underpass or culvert), and
smoothed with a brush. It should be fine enough to detect the tracks of small
vertebrates such as mice or amphibians, or even macroinvertebrates. The pass
must be reviewed every 1–2 days and, if necessary, the material must be removed
and extra material added (Yanes et al. 1995; Rodríguez et al. 1996; Baofa et al.
2006). This method, combined with strips of soot-coated paper, as well as
4 Railways as Barriers for Wildlife: Current Knowledge
49