Analysis of linear road barriers and their permeability for wildlife species in the Czech landscape

The road networks, especially motorways and expressways, are the most harmful anthropogenic barriers to biodiversity and landscape and contribute to landscape fragmentation.  This fact required to add specific activities in the framework of the project "A complex approach to the protection of fauna of terrestrial ecosystems from landscape fragmentation in the Czech Republic" (see another presentation for information on the overall concept of the project). These activities covering the whole territory of the Czech Republic are focused on the identification, analysis and evaluation of linear barriers (incl. historical development) and on the identification of suitable or potential passages in infrastructure. Knowledge and assessment of the current level of landscape fragmentation and its dynamics is a prerequisite for the main activity of the project, i.e. the definition of habitats of specially protected species.

The identification of linear barriers is processed through a spatial geodatabase representing the evolution of the road network in different periods of time. This linear layer includes all dual carriageways – motorways, expressways and some 1st class roads. These road categories can be considered as virtually complete barriers to the migration of wildlife without accompanying measures. The geometry of the layer was digitized employing actual aerial photos. Historical information has been specified using historical topographic maps and the opening date of each section was determined from historical publications and the contemporary press. For planning purposes the database was also extended to motorways and expressways that are only planned on the basis of spatial land-use planning documents, particularly on national and regional levels. The road network covered in this activity includes approximately 1,600 km of existing and 1,250 km of planned carriageways.

The activity following the analysis of barriers is to identify the spatial position and to evaluate the potential of individual passages on the roads. The two older thematic databases with limited territorial coverage (one maintained by the Transport Research Centre and another by the Nature Conservation Agency of the Czech Republic) were merged and expanded to cover the entire mapped network. Considered as potential passages were all objects with dimensions meeting the minimum requirements for the passage of larger mammals (width 12 m and height 3 m for common length of passage 25 m – permeability index 1.4). Important objects that are located on potential migration routes were visited in the field. The whole database of passages currently contains 1,076 objects (incl. impassable ones) and is accompanied by an extensive photo gallery of individual objects composed of both internal and publicly available photos.

These two layers are used in defining the spatial layer of habitats of specially protected species in order to allow an easy identification of conflict points in the intersection of green and transport infrastructure. We assume, however, that their use will be broader in other research activities, therefore both layers will be continuously updated and expanded to follow further development of transport infrastructure, its construction and technical layout.

road network, permeability, wildlife, the Czech Republic