How to Mitigate Wildlife Mortality in Railways?
Over the last few decades, research and investment on mitigation measures to
reduce wildlife mortality on roads have increased greatly (Jackson and Griffin 2000;
Glista et al. 2009; Polak et al. 2014; Kociolek et al. 2015; Ward et al. 2015). In
railways the efforts to increase wildlife safety have not been as considerable (van
der Grift 1999; Dorsey et al. 2015), and these efforts have been concentrated mostly
on mitigating the impacts on existing railways, ignoring the expansion of the
high-speed railway network (Dorsey et al. 2015). An important difference between
roads and railways is that in the latter, the speed and trajectory of a train cannot be
changed to avoid collisions; therefore, mitigation measures must rely almost
entirely on preventing the animals from entering or remaining on the train tracks.
Crossing Structures
The structures that facilitate wildlife crossing of railways can be part of the original
engineering design of the infrastructure; these include culverts or bridges over roads
or rivers, even when that was not their original purpose. At other times, these
structures can become wildlife crossing locations with just minor adaptations, as
happens with dry ledges. Alternatively, structures can be built with the specific goal
of enabling movements across the linear infrastructure, usually designated as
wildlife underpasses or overpasses.
Although crossing structures contribute to mitigating both mortality and barrier
effects of linear infrastructures (Dorsey et al. 2015), their main role has been
focused on barrier effects, ensuring connectivity through the landscapes crossed by
railways and roads (Glista et al. 2009; Jackson and Griffin 2000; van der Ree et al.
2008). In this book, the application of crossing structures as a mitigation measure in
railways is described in greater detail in Chap. 4. Here, we give a short description
of the most frequently used crossing structures, and how they may help reduce
wildlife mortality on railways.
Pipe culverts are small structures designed to let water flow under the railway,
being regularly flooded during the rainy seasons. Pipe culverts form part of the
design of most linear infrastructures and are sometimes used by small animals
(Glista et al. 2009; Jackson and Griffin 2000). The efficiency of pipe culverts in
reducing mortality would increase if it were associated with railway exclusion
methods (see section below).
Box culverts are also designed for water drainage, and being larger than pipe
culverts, often remain dry except in periods of heavy run-off. Box culverts are
generally better as crossing structures than pipe culverts (Glista et al. 2009).
Culverts can be adapted before or after construction to facilitate their use by
wildlife (Clevenger and Waltho 1999; Jackson and Griffin 2000; Rodríguez et al.
1996), namely by (1) including dry ledges, (2) modifying habitats at entrances,
3 Methods to Monitor and Mitigate Wildlife Mortality in Railways
31
Over the last few decades, research and investment on mitigation measures to
reduce wildlife mortality on roads have increased greatly (Jackson and Griffin 2000;
Glista et al. 2009; Polak et al. 2014; Kociolek et al. 2015; Ward et al. 2015). In
railways the efforts to increase wildlife safety have not been as considerable (van
der Grift 1999; Dorsey et al. 2015), and these efforts have been concentrated mostly
on mitigating the impacts on existing railways, ignoring the expansion of the
high-speed railway network (Dorsey et al. 2015). An important difference between
roads and railways is that in the latter, the speed and trajectory of a train cannot be
changed to avoid collisions; therefore, mitigation measures must rely almost
entirely on preventing the animals from entering or remaining on the train tracks.
Crossing Structures
The structures that facilitate wildlife crossing of railways can be part of the original
engineering design of the infrastructure; these include culverts or bridges over roads
or rivers, even when that was not their original purpose. At other times, these
structures can become wildlife crossing locations with just minor adaptations, as
happens with dry ledges. Alternatively, structures can be built with the specific goal
of enabling movements across the linear infrastructure, usually designated as
wildlife underpasses or overpasses.
Although crossing structures contribute to mitigating both mortality and barrier
effects of linear infrastructures (Dorsey et al. 2015), their main role has been
focused on barrier effects, ensuring connectivity through the landscapes crossed by
railways and roads (Glista et al. 2009; Jackson and Griffin 2000; van der Ree et al.
2008). In this book, the application of crossing structures as a mitigation measure in
railways is described in greater detail in Chap. 4. Here, we give a short description
of the most frequently used crossing structures, and how they may help reduce
wildlife mortality on railways.
Pipe culverts are small structures designed to let water flow under the railway,
being regularly flooded during the rainy seasons. Pipe culverts form part of the
design of most linear infrastructures and are sometimes used by small animals
(Glista et al. 2009; Jackson and Griffin 2000). The efficiency of pipe culverts in
reducing mortality would increase if it were associated with railway exclusion
methods (see section below).
Box culverts are also designed for water drainage, and being larger than pipe
culverts, often remain dry except in periods of heavy run-off. Box culverts are
generally better as crossing structures than pipe culverts (Glista et al. 2009).
Culverts can be adapted before or after construction to facilitate their use by
wildlife (Clevenger and Waltho 1999; Jackson and Griffin 2000; Rodríguez et al.
1996), namely by (1) including dry ledges, (2) modifying habitats at entrances,
3 Methods to Monitor and Mitigate Wildlife Mortality in Railways
31