GRAPHAB

Using landscape graphs to evaluate and mitigate the impacts of major transport infrastructure on species

The objective of the Graphab project is to propose and test a set of methods to estimate the impact of major transport infrastructures on the distribution of species. This approach is based on the observation that classical impact studies are limited to an area close to the infrastructure route, whereas a barrier effect can occur over a longer period if the species are highly dependent on their ecological network. The approach chosen to model ecological networks is that of landscape graphs, which have been coupled with species distribution models. By comparing the results of distribution models diachronically, before and after the establishment of an infrastructure, it is possible to map its impact and estimate its disturbance distance.

This research has been applied to several species in a vast study area surrounding the eastern branch of the Rhine-Rhone high-speed line. Tests of the methodological protocol first focused on a virtual species, whose population was simulated so as to depend on a strong connectivity. Two real species were then analyzed. For the tree frog, a frog species whose presence has been dependent on connectivity at a local scale, the estimated impact of the Rhine-Rhone high-speed line is small (about 1 km). For the little rhinolophe, a bat species whose location of deposits has been sensitive to long-distance connectivity, LGV should have a longer-term impact.

The set of methods put in place gave rise to the creation of a software tool, Graphab 1.0. This tool facilitates the exploration of landscape graphs and proposes an original gateway with distribution models. All the results obtained invite further tests, particularly to use the models in an operational framework for the development of transport infrastructure. In the long term, new field campaigns would be useful to validate the impact estimates resulting from the modelizations.

Valorisation