Germany is a densely populated industrialised country with a highly developed transport network. In 2009, the inter-urban road network (federal highways and federal, regional and district roads) had a total length of 231,072 kilometres. Habitat fragmentation caused by the transport network as well as an increasing traffic density have, to some extent, resulted in the isolation and degradation of remaining habitats for animals and plants. It is mainly the barrier effect of roads that impedes the exchange within and among populations and the colonisation of new habitats, leading to an insufficient genetic exchange in animal and plant species. In addition, high traffic density causes a substantial number of animal casualties.