Disturbance
Traffic noise, vibrations, chemical pollution, and human presence can impact animal populations living close to railways, contributing to the barrier effects (van der
Grift 1999; Dorsey et al. 2015; see a more complete discussion in the Chap. 6).
These impacts can be divided into those related to siting and construction, and those
related to the operation of the railway line (De Santo and Smith 1993; see also
Chap. 12). The former has received little attention, likely because they are considered short-term, but they can nevertheless affect local animal populations. For
instance, although construction was halted during the migration period of the
human-wary Tibetan antelopes (Pantholops hodgsonii) in China, the animals did
not use wildlife passes because of the presence of machinery and debris (Xia et al.
2007). However, this species finally adapted to the presence of the railway and used
wildlife passes once the was train operative (Yang and Xia 2008).
Among the long-term disturbances related to barrier effects, one of the most
significant seems to be the noise produced by trains, because railways’ right-of-way
has little vegetation to absorb the sound, as it is frequently mowed. Studies to date
have been carried out with simple census-based approaches, and have provided
contradictory findings. For instance, whereas in the Netherlands, Waterman et al.
(2002) found a reduction in the density of meadow birds close to railways,
Wiącek et al. (2015), counting forest birds at 30, 280 and 530 m from the tracks,
found higher species richness close to the railway in a Polish forest crossed by a
railway. In fact, guilds like insectivorous or those ecotone-specialists were more
common close to railways, and species with low-frequency calls were not averse to
it (Wiącek et al. 2015). In a study in a Brazilian Atlantic forest, Cerboncini et al.
(2016) did not find an effect of traffic noise (up to 120 dB, higher close to the track)
on small mammals, probably because of the infrequent train passage.
Several field studies did not explore the potential causes of the abundance patterns
observed and the distance to railway tracks. For instance, Li et al. (2010) found higher
ground-dwelling bird richness and abundance in China close to the railway when
sampled at 0, 300, 600, 900 and 1,200 m. In a study on the rodent community in the same
railway, Qian et al. (2009) found no effect on species composition or densities at 50, 200
and 500 m from the railway in non-grazing areas, but grazing-disturbed areas showed
different species ratios (Qian et al. 2009). The density of urban foxes (Vulpes vulpes) in
the UK was similar in squares with and without railways (Trewhella and Harris 1990);
however, in areas with poor habitat quality, fox dens were commonly placed in railway
banks, most likely because they acted as refuges (Trewhella and Harris 1990).
Mortality
Chapters 2 and 3 deal exclusively with the impact of railways on wildlife mortality;
however, because we consider mortality to be a barrier effect, and in order to ensure
that current chapter is self-contained, we now summarize the main results.
46
R. Barrientos and L. Borda-de-Água
Traffic noise, vibrations, chemical pollution, and human presence can impact animal populations living close to railways, contributing to the barrier effects (van der
Grift 1999; Dorsey et al. 2015; see a more complete discussion in the Chap. 6).
These impacts can be divided into those related to siting and construction, and those
related to the operation of the railway line (De Santo and Smith 1993; see also
Chap. 12). The former has received little attention, likely because they are considered short-term, but they can nevertheless affect local animal populations. For
instance, although construction was halted during the migration period of the
human-wary Tibetan antelopes (Pantholops hodgsonii) in China, the animals did
not use wildlife passes because of the presence of machinery and debris (Xia et al.
2007). However, this species finally adapted to the presence of the railway and used
wildlife passes once the was train operative (Yang and Xia 2008).
Among the long-term disturbances related to barrier effects, one of the most
significant seems to be the noise produced by trains, because railways’ right-of-way
has little vegetation to absorb the sound, as it is frequently mowed. Studies to date
have been carried out with simple census-based approaches, and have provided
contradictory findings. For instance, whereas in the Netherlands, Waterman et al.
(2002) found a reduction in the density of meadow birds close to railways,
Wiącek et al. (2015), counting forest birds at 30, 280 and 530 m from the tracks,
found higher species richness close to the railway in a Polish forest crossed by a
railway. In fact, guilds like insectivorous or those ecotone-specialists were more
common close to railways, and species with low-frequency calls were not averse to
it (Wiącek et al. 2015). In a study in a Brazilian Atlantic forest, Cerboncini et al.
(2016) did not find an effect of traffic noise (up to 120 dB, higher close to the track)
on small mammals, probably because of the infrequent train passage.
Several field studies did not explore the potential causes of the abundance patterns
observed and the distance to railway tracks. For instance, Li et al. (2010) found higher
ground-dwelling bird richness and abundance in China close to the railway when
sampled at 0, 300, 600, 900 and 1,200 m. In a study on the rodent community in the same
railway, Qian et al. (2009) found no effect on species composition or densities at 50, 200
and 500 m from the railway in non-grazing areas, but grazing-disturbed areas showed
different species ratios (Qian et al. 2009). The density of urban foxes (Vulpes vulpes) in
the UK was similar in squares with and without railways (Trewhella and Harris 1990);
however, in areas with poor habitat quality, fox dens were commonly placed in railway
banks, most likely because they acted as refuges (Trewhella and Harris 1990).
Mortality
Chapters 2 and 3 deal exclusively with the impact of railways on wildlife mortality;
however, because we consider mortality to be a barrier effect, and in order to ensure
that current chapter is self-contained, we now summarize the main results.
46
R. Barrientos and L. Borda-de-Água