connected by functional relationships (“links”). It provides a simplified representation
of ecological networks and is considered an interesting trade-off between information
content and data requirements (Calabrese and Fagan 2004). Several metrics can be
computed at global level to assess connectivity for the entire graph or at local level for
individual nodes or links (Galpern et al. 2011). Graph-based studies have been used to
identify the key elements for connectivity (Bodin and Saura 2010; Saura and
Pascual-Hortal 2007), to evaluate the importance of connectivity for species distribution (Foltête et al. 2012a; Galpern and Manseau 2013; Lookingbill et al. 2010), to
assess the impact assessment of a given development on connectivity (Clauzel et al.
2013; Fu et al. 2010; Girardet et al. 2013; Gurrutxaga et al. 2011; Liu et al. 2014)
or to propose mitigation measures for improving connectivity (Clauzel et al. 2015a, b;
Girardet et al. 2016; Mimet et al. 2016).
In this case study, we propose to assess and to mitigate the potential impact of a
HSR line on connectivity for the European tree frog (Hyla arborea) in eastern
France. Populations of this species are declining in western Europe due to several
causes: climate change, increased UV-radiation (Alford and Richards 1999), predation or competition, pollution and eutrophication of ponds (Borgula 1993),
road-kill (Elzanowski et al. 2008), and above all the destruction and fragmentation
of its habitat (Andersen et al. 2004; Cushman 2006; Vos and Stumpel 1996). In the
region under study, the development of the HSR line and consecutive changes in
connectivity may therefore impact the viability of tree frog populations.
The analysis consists of modeling the ecological network of the European tree frog
with and without the HSR line in the landscape map. The presence of the HSR line
probably entails a loss of connectivity among suitable habitats thus restricting the
potential movements of the species. Comparison of the connectivity values between
the two graphs provides an assessment of the changes in connectivity induced by the
HSR line. The analysis is supplemented by a search for the best locations for
amphibian crossing structures in order to improve connectivity. This study is based
on a predictive modelling approach that estimates a potential impact but does not
measure a real impact. This approach is therefore put in place before the construction
of an infrastructure and allows areas potentially affected by isolation to be mapped.
Materials and Methods
Data Preparation
Study Area
Our study was carried out in a zone of 4600 km
2 in the Burgundy-Franche-Comté
region of eastern France (Fig. 13.1). In this zone altitude ranges from 184 to 768 m,
the landscape mosaic is dominated by forests (42% of total area), intensive agriculture (27%) and grasslands (20%). This area is strategic for environmental conservation because it contains many threatened species of birds (such as the little
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217
of ecological networks and is considered an interesting trade-off between information
content and data requirements (Calabrese and Fagan 2004). Several metrics can be
computed at global level to assess connectivity for the entire graph or at local level for
individual nodes or links (Galpern et al. 2011). Graph-based studies have been used to
identify the key elements for connectivity (Bodin and Saura 2010; Saura and
Pascual-Hortal 2007), to evaluate the importance of connectivity for species distribution (Foltête et al. 2012a; Galpern and Manseau 2013; Lookingbill et al. 2010), to
assess the impact assessment of a given development on connectivity (Clauzel et al.
2013; Fu et al. 2010; Girardet et al. 2013; Gurrutxaga et al. 2011; Liu et al. 2014)
or to propose mitigation measures for improving connectivity (Clauzel et al. 2015a, b;
Girardet et al. 2016; Mimet et al. 2016).
In this case study, we propose to assess and to mitigate the potential impact of a
HSR line on connectivity for the European tree frog (Hyla arborea) in eastern
France. Populations of this species are declining in western Europe due to several
causes: climate change, increased UV-radiation (Alford and Richards 1999), predation or competition, pollution and eutrophication of ponds (Borgula 1993),
road-kill (Elzanowski et al. 2008), and above all the destruction and fragmentation
of its habitat (Andersen et al. 2004; Cushman 2006; Vos and Stumpel 1996). In the
region under study, the development of the HSR line and consecutive changes in
connectivity may therefore impact the viability of tree frog populations.
The analysis consists of modeling the ecological network of the European tree frog
with and without the HSR line in the landscape map. The presence of the HSR line
probably entails a loss of connectivity among suitable habitats thus restricting the
potential movements of the species. Comparison of the connectivity values between
the two graphs provides an assessment of the changes in connectivity induced by the
HSR line. The analysis is supplemented by a search for the best locations for
amphibian crossing structures in order to improve connectivity. This study is based
on a predictive modelling approach that estimates a potential impact but does not
measure a real impact. This approach is therefore put in place before the construction
of an infrastructure and allows areas potentially affected by isolation to be mapped.
Materials and Methods
Data Preparation
Study Area
Our study was carried out in a zone of 4600 km
2 in the Burgundy-Franche-Comté
region of eastern France (Fig. 13.1). In this zone altitude ranges from 184 to 768 m,
the landscape mosaic is dominated by forests (42% of total area), intensive agriculture (27%) and grasslands (20%). This area is strategic for environmental conservation because it contains many threatened species of birds (such as the little
13 Evaluating and Mitigating the Impact of a High-Speed Railway …
217