SUBJECT: Permeability of Highway Net in the Czech Republic
AUTHOR: Vaclav Hlavac, Agency of Nature Conservation and Landscape Protection of the Czech Republic, Czech Republic

SUMMARY: Busy overland roads, especially highways and motorways, create barriers for the migration of wild animals, causing fragmentation of their habitat and, ultimately, of populations. Isolated populations are particularly prone to extinction due to a number of factors, collectively termed as “island effects”. There are currently about 950 km of motorways in the Czech Republic, with another 800 km planned to be built within the next years 15. A large study concerning habitat fragmentation was recently carried out in the Czech Republic. This study concluded that only 30% of the total length of motorways and motorways in the Czech Republic are permeable for big mammals as red deer, moose and large carnivores. Detailed analysis of the whole of the Czech Republic showed seven sections, where impermeable motorways cross important migration corridors for big mammals. For these sections, restoration plans for permeability is prepared.

KEYWORDS: habitat fragmentation, big mammals, motorway, fauna passages, fauna causalities, monitoring, permeability, migration, linear barrier, mitigation, Czech Republic.

Busy overland roads, especially highways and motorways, create barriers for the migration of wild animals, causing fragmentation of their habitat and, ultimately, of populations. The increasingly denser motorway network then turns the originally open landscape into a system of isolated “islands”. Isolated populations are particularly prone to extinction due to a number of factors, collectively termed as “island effects”. There are currently about 950 km of motorways in the Czech Republic, another 800 km are planned to be built within the next 15 years. As heavily used undivided roads can become barriers for wildlife as well, habitat fragmentation is a very much a current problem in the Czech Republic. A large study concerning the habitat fragmentation was recently carried out in the Czech Republic. This study was focused on two aims: To clarify the influence of existing motorway net on habitat fragmentation and on populations of target species; and to come up with guidelines on how to minimize the barrier effect when building new roads.

Habitat fragmentation mainly influences species inhabiting large areas with a relatively low population density; therefore, the most threatened species are usually large mammals. All available data about distribution, migration and current numbers of populations of all species of big mammals were collected in the Czech Republic. Special attention was paid to badger (Meles meles), otter (Lutra lutra), red fox (Vulpes vulpes), wolf (Canis lupus), lynx (Lynx lynx), brown bear (Ursus arctos), wild boar (Sus scrofa), roe deer (Capreolus capreolus), red deer (Cervus elaphus) and moose (Alces alces).
Based on the data about the distribution and migration of big mammals, the territory of the Czech Republic was divided into five categories – from the most important areas to areas without any importance. For each category special recommendations about density of wildlife passages, which has to be build on motorways in these areas, were prepared.

The next task was an assessment of minimum parameters of fauna passages for different species. This evaluation was based on observations from 100 bridges distributed evenly across the motorway system. For this study, bridges crossing water streams, valleys and small forest- and agricultural roads were chosen, as animals often use these bridges in order to cross the motorway. Each of these bridges was visited a minimum of three times when snow cover was present. On the basis of this study, recommendations for minimum parameters of underpasses for different mammals were prepared.
In 1998-1999, an intensive research programme linked with physical checks of all 850 motorway bridges over the entire Czech Republic was carried out. This study concluded that only 40% of the total length of motorways in the Czech Republic is permeable for medium-sized animals such as roe deer and wild boar, and that only 30% is permeable for red deer, moose and large carnivores. The present motorway network does not represent a significant barrier for animals the size of a fox, badger or otter, as these species are able to use large numbers of small bridges and culverts (they can usually find a safe crossing possibility each 1-2km).
On the basis of the data mentioned above, large monitoring of faunal casualties and analysis of traffic accidents caused by wild animals, the critical sections on existing motorways were identified. Detailed analysis of the whole of the Czech Republic showed seven sections where impermeable motorways cross important migration corridors for big mammals. Restoration plans for permeability are being prepared for these sections.

References:
Bekker H. & Vastenhout M. (1995): Nature across motorways, Rijkswaterstaat. Dienst Wegen Waterbouwkunde, Delft,
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Hlaváè, V. & Andìl, P. (2002) On the Permeability of Roads for Wildlife: a Handbook. Agency for Nature Conservation and Landscape Protection of the Czech Republic and EVERNIA s.r.o. Liberec
Pfister H. P., Keller V., Georgii B. & Reck H. (1997): Bio-ökologische Wirksamkeit von Grünbrücken über Verkerswege, Forschungsberichte aus dem Forschungsprogramm