Green bridges/ wildlife crossings

Green bridges/ wildlife crossings
Wildlife crossings should be located at known animal crossing points or specific “conflict points” in the transregional transport network. © Sina Hölscher

Involved sectors

Forestry, Hunting, Spatial planning, Nature protection, Transport, Other: NGO, Districts

Affected habitats

Areas for settlements and transport

Description

A wildlife crossing, or green bridge, is intended to serve as an aid to wild animals, enabling them to cross busy transport routes such as motorways, highways and even railway lines safely and thus mitigating the impacts of increasing landscape fragmentation. The position of these crossings is particularly important: wildlife crossings should be located at known animal crossing points or specific “conflict points” in the transregional transport network. In order to screen the view of the transport routes to be crossed, the edges of the bridge are often planted with hedgerows, with much of the rest of the surface of the bridge being covered in vegetation as well. There are now numerous studies which provide information about required dimensions, vegetation, technical construction details etc.

Impact

Impact in particular on Small mammals, Big mammals, Reptiles, Amphibians, Insects
Ecological impact  
Reduction of fragmentation or creation of new valuable habitats Green bridges are a suitable method of mitigating the fragmentation effects of roads, connecting habitats across roads and safeguarding regional and transregional migration routes.
Improvement or preservation of habitats The bridges are particularly effective if they do not appear to be foreign bodies or separate biotopes but are designed as habitats and thus meet the habitat requirements of smaller vertebrate or invertebrate species as well.
Element of ecological network If integrated into a biotope networking strategy, the crossing aids become important sections of corridors.
Other From a nature conservation perspective, key aspects such as fragmentation of species' partial habitats, impediments to large-scale annual migrations, impediments to the (re-) dispersion of animal species and thus the new colonisation or recolonisation of habitats by species which had previously been eliminated or had died out should also be taken into consideration during planning.
Time of realisation for measure Months: Once built, the bridge can be used immediately. Guide structures leading to it facilitate animals' acceptance.
Impact scope Local (municipality): Depending on the species and the importance of the crossing point, the impact can range from local to transregional.

Implementation

Implementation period Months: Planning and construction of these crossing aids are very costly and time-consuming.
Frequency Non-recurring: Should be accompanied by monitoring of effectiveness.

Economic and legal aspects

Costs Very high (>1 Mio. EUR): Building costs of a green bridge amount to € 1-5 million. Ongoing maintenance costs must also be considered.
Socio-economic impacts Low: Reduction in number of accidents involving deer (physical damage, loss of game, personal injury ...)
Sources of financing Other private sources, Public: local, Public: regional, Public: national, Public: European
Legal situation Legal provisions exist indirectly via the European and national level relating to the spatial linkage of protected areas.

Further information

Evaluation Studies on the biological effectiveness of green bridges have shown that they make a major contribution to habitat connectivity. They are not only used by large animals but also by invertebrates such as butterflies, spiders and beetles. Green bridges do not only have a connecting function, they also help to reduce the number of accidents involving deer.
Information Austria: Detailed recommendations in core study: VÖLK, F.; GLITZNER, I. & WÖSS, M. (2001): Kostenreduktion bei Grünbrücken durch deren rationellen Einsatz. Kriterien – Indikatoren – Mindeststandards. Straßenforschung, Heft 513. Bundesministerium für Verkehr, Innovation und Technologie, Wien. » http://www.fsv.at/
Contact Austria: A wealth of key information, literature, links and case studies is available from Austrian Federal Environment Agency (http://www.umweltbundesamt.at/)

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