e.g. the zebra mussel (Dreissena polymorpha) in water treatment works (Elliott
et al. 2005). However, there are also many indirect damages that are difficult to
quantify because they would require a deeper understanding of the
ecosystem-economy relationship (Bradshaw et al. 2016). Furthermore, many
invasive species are also vectors of human diseases, such as malaria, plague, typhus
or yellow fever, and their transportation may result in outbreaks of these infections
in previously unsuspected areas (Lounibos 2010; Capinha et al. 2014). Also,
invasive species may cause ecological or landscape changes that have negative
implications for human safety, these can assume multiple forms, such as the promotion of pathogen eruptions (Vanderploeg et al. 2001), or an increase in the
vulnerability of landscapes to natural hazards such as fires (Berry et al. 2011).
Importantly, many of the future impacts of non-native species may still remain
unknown. For instance, the increased profusion of invasive species may render a
cascading effect on the vulnerability of ecosystems, i.e. by making these even more
susceptible to future impacts. Climate change is a further source of concern.
Changes in climatic patterns altering the geography of the areas that can be invaded
may put additional pressures on native biodiversity. Understanding how these
processes will interact in the future to determine the impacts of biological invasions
is challenging. In fact, many future invasions may have already been set in motion,
i.e. many non-native species are currently in a lag-phase, i.e. with little or no
increase in species occurrence, to be followed by an increase-phase in which
species occurrence and invasiveness rises rapidly before becoming invaders (Aikio
et al. 2010; Essl et al. 2011).
Without increased efforts to manage non-native species in transportation
infrastructures, including in vehicles, transported cargo and verges, the number of
invasive species will likely continue to grow steadily (Keller et al. 2011). Hence,
more effective policies to reduce the transport and release of non-native species, and
to manage those already established, should become a priority (Pimentel et al. 2005;
Keller et al. 2011).
Non-native Hitchhikers: Transportation Vehicles
as Vectors of Stowaway Species
The surroundings of transportation infrastructures (e.g. verges and embankments)
often host a high diversity of non-native species (Gelbard and Belnap 2003; Hansen
and Clevenger 2005), in many cases due to their transportation as stowaways in
vehicles. Species can be accidentally moved by a vehicle in many different ways,
e.g. snails and slugs clinging to a train, insects flying inside a vehicle, plant seeds in
passengers’ boots, or any organism that makes frequent use of cargo yards and that
is loaded unintentionally loaded with the cargo. Nevertheless, despite the range of
possibilities, the movement of stowaway fauna and flora is poorly documented for
terrestrial transportation systems. This is in contrast with aquatic transportation,
especially maritime, for which there is a large body of research, particularly
5 Aliens on the Move: Transportation Networks and Non-native …
69
et al. 2005). However, there are also many indirect damages that are difficult to
quantify because they would require a deeper understanding of the
ecosystem-economy relationship (Bradshaw et al. 2016). Furthermore, many
invasive species are also vectors of human diseases, such as malaria, plague, typhus
or yellow fever, and their transportation may result in outbreaks of these infections
in previously unsuspected areas (Lounibos 2010; Capinha et al. 2014). Also,
invasive species may cause ecological or landscape changes that have negative
implications for human safety, these can assume multiple forms, such as the promotion of pathogen eruptions (Vanderploeg et al. 2001), or an increase in the
vulnerability of landscapes to natural hazards such as fires (Berry et al. 2011).
Importantly, many of the future impacts of non-native species may still remain
unknown. For instance, the increased profusion of invasive species may render a
cascading effect on the vulnerability of ecosystems, i.e. by making these even more
susceptible to future impacts. Climate change is a further source of concern.
Changes in climatic patterns altering the geography of the areas that can be invaded
may put additional pressures on native biodiversity. Understanding how these
processes will interact in the future to determine the impacts of biological invasions
is challenging. In fact, many future invasions may have already been set in motion,
i.e. many non-native species are currently in a lag-phase, i.e. with little or no
increase in species occurrence, to be followed by an increase-phase in which
species occurrence and invasiveness rises rapidly before becoming invaders (Aikio
et al. 2010; Essl et al. 2011).
Without increased efforts to manage non-native species in transportation
infrastructures, including in vehicles, transported cargo and verges, the number of
invasive species will likely continue to grow steadily (Keller et al. 2011). Hence,
more effective policies to reduce the transport and release of non-native species, and
to manage those already established, should become a priority (Pimentel et al. 2005;
Keller et al. 2011).
Non-native Hitchhikers: Transportation Vehicles
as Vectors of Stowaway Species
The surroundings of transportation infrastructures (e.g. verges and embankments)
often host a high diversity of non-native species (Gelbard and Belnap 2003; Hansen
and Clevenger 2005), in many cases due to their transportation as stowaways in
vehicles. Species can be accidentally moved by a vehicle in many different ways,
e.g. snails and slugs clinging to a train, insects flying inside a vehicle, plant seeds in
passengers’ boots, or any organism that makes frequent use of cargo yards and that
is loaded unintentionally loaded with the cargo. Nevertheless, despite the range of
possibilities, the movement of stowaway fauna and flora is poorly documented for
terrestrial transportation systems. This is in contrast with aquatic transportation,
especially maritime, for which there is a large body of research, particularly
5 Aliens on the Move: Transportation Networks and Non-native …
69