6533b871fe1ef96bd12d2194

RESEARCH PRODUCT

Graphab 2

subject

description

For some ten years, landscape graphs have been widely used for modeling ecological networks and measuring landscape connectivity from an operational perspective. A landscape graph is a set of nodes (habitat patches for a given species or group species) potentially connected by links representing the functional connectivity between each pair of nodes. With their simple design and their ecological relevance, graph-based methods can serve as a guide for planning decision-making, especially for the conservation of ecological networks. In this perspective, Graphab 2 project aims to use landscape graphs to assess the impact of transport infrastructures on the functionality of ecological networks, and to provide guidance for locating mitigation (wildlife crossing structures) and compensation (habitat restoration/creation) measures.In the first part, the project was focused on the use of genetic data acquired for a bat species (the lesser horseshoe) in Franche-Comté. The aim was to develop a protocol to assess the impact of a transport infrastructure on the degree of isolation of subpopulations. The results showed that there was a close link between the spatial structure of genetic data and the configuration of the graph representing the ecological network of the lesser horseshoe bat. This statistical link was first highlighted the barrier effect of the A36 highway on the species dispersion flow. It was then used to estimate the potential effect of the eastern branch of the Rhine-Rhône TGV recently put into service. According to the results, the TGV line could have a cumulative effect with the A36 highway, by isolating the horseshoe bat roots located along the lower valley of the Doubs.In the second part, landscape graphs were used as a tool for guiding decision making for the conservation of species whose networks were threatened by infrastructures. In a sensitive natural area in Franche-Comté, where an amphibian network (including the tree frog) was affected by the implementation of the TGV Rhine-Rhône, a protocol was set up to identify the best locations for the creation of new ponds. The comparison between modeling results and the locations suggested by field experts confirmed the relevance of the proposed method. In the mountainous Yunnan Province (West of China), a study focused on the ecological network of an endemic primate, the snub-nosed monkey, impacted by road development projects. Several scenarios were compared to assess the partial transfer of traffic to a tunnel section, potentially combining with reforestation measures. The results led to prioritize scenarios based on their ability to restore connectivity of the species network.In the third part, the project focused on the potential of landscaped graphs in the decision support for the management of transport infrastructures. It provided analysis without reference to a specific species, but integrating generic species profiles. Several studies focused on the location of wildlife crossing structures. Along the Rhine-Rhone TGV (eastern branch), a method was set up to identify multiple points of additional structures, using forest species profiles. In the Grésivaudan Valley (Isère) crossed by A41 and A48 highways, the same approach was applied to locate the most relevant points for eight different species profiles. The results led to identify a strategic zone for connectivity restoration for most of the considered species.All researches in this project were accompanied by the development of Graphab software. This free tool has found a positive response in the scientific community and it is currently used in many studies about ecological connectivity and land use planning issues.