Inventory and Typology of Fauna Passages on French Transport Infrastructures
French transport infrastructures network increased significantly since 1980th. The french roads network is one of the densest in the world, nearly 1 million kilometres long. Habitat fragmentation by transport infrastructure is recognised as one of the prime cause of eroding biodiversity in the industrialized countries. Providing links between habitats can directly reduce fragmentation. Thus, fauna passages need to be built to mitigate the increasing negative barrier effect of infrastructures on wildlife and maintain connectivity.
In 2000, 400 crossing structures (fauna passages and others structures of permeability) were inventoried on French transport infrastructures. In 2006, more exhaustive surveys listed 399 structures only in Nord-Pas-de-Calais and Picardie regions, both described in the present paper. Therefore, a tool becomes necessary to evaluate the transpar¬ency for wildlife of the whole French transport infrastructures.
The main objective of the study is to carry out a database to inventory the structures of transparency, define their effectiveness as fauna passage and share comparable information amongst transport stakeholders. This project responds to one of the actions of the linear transport action plan adopted by France in November 2005, planned within the framework of the preservation of biodiversity (French strategy adopted in 2004). The aim is the implementation of appropriate measures for preservation of biodiversity during construction, maintenance and exploitation phases.
In this paper, we describe the first stage of work conducted to identify the number and type of fauna passages (via¬duct, bridge, pipe conduit, mixed, specific, overpass, underpass, etc.) on the French transport network (roads, railways and waterways). First results concern a pilot area - Nord-Pas-de-Calais and Picardie regions - which presented the most exhaustive data. They show many difficulties related to data heterogeneity, to old and partial data, and to distinguish structures and integrate them in the typology. Moreover, this step had to be delay because of the new management organization of the national road network (decentralization and reorganization of public authorities in charge).
Once the geo-localised database will be achieved, we will try to implement a monitoring system on field to specify the effectiveness of different types of passages. In addition, comparison between crossing structures map, biological corridor maps at departmental and regional scale, and non-fragmented territory map (MEDD, 2007) will allow us to identify future fragmentation black spots.