Mapping the French green infrastructure – an exercise in homogenizing heterogeneous regional data

ABSTRACT

To preserve and restore ecosystems, public environmental policies on the international level now encourage the creation of Green Infrastructure, i.e. networks composed of areas where animal and vegetal species can live (habitat patches) and corridors to circulate between them. In France, each regions, the first subnational administrative level, identified existing habitat patches and corridors in their territories using flexible guidelines. This resulted in heterogeneous data, raising the question of their consistent mapping at a supra-regional level. To answer this question, this study first focuses on the habitat patches of two adjacent regions and explores three ways of homogenizing the map. The first method consists in generalizing the more detailed data using morphologic operators. The second method consists in graphically refining the less detailed data by filling the areas with patterns taken from the more detailed data. The third method consists in drastically changing the level of abstraction of the data from both regions by rasterizing the space. Based on those experiments, we applied the most appropriate method to data collected by all the regions of continental France, a step which itself raises new issues concerning data harmonization and parameters settings.

RÉSUMÉ

Afin de préserver ou restaurer les écosystèmes, les politiques publiques environnementales incitent à la création de trames écologiques, c'est-à-dire des réseaux composés de zones où les animaux et végétaux vivent (réservoirs de biodiversité) et de corridors les reliant. En France, les régions ont chacune défini ces réservoirs et corridors sur leur territoire en suivant des méthodologies différentes, dans le cadre de la politique de la Trame verte et Bleue. Il en a résulté des données hétérogènes, ce qui soulève la question de leur cartographie cohérente à un niveau supra-régional. Pour répondre à cette question, cette étude s'intéresse d'abord à la cartographie de deux régions adjacentes, et explore trois méthodes différentes pour homogénéiser la carte. La première méthode consiste à généraliser les données les plus détaillées à l'aide d'opérateurs morphologiques. La deuxième méthode consiste à affiner le rendu graphique des données les moins détaillées en remplissant les surfaces avec des patrons graphiques issus des données les plus détaillées. La troisième méthode consiste à changer plus drastiquement le niveau d'abstraction des données pour les deux régions, en rastérisant l'espace. A partir de ces expérimentations, la méthode la plus appropriée a été appliquée à l'ensemble des données des régions de France continentale, une étape qui a fait surgir de nouvelles difficultés liées à l'harmonisation des données et le choix des paramètres.

KEYWORDS:

• Cartography
• harmonization
• generalization
• green infrastructure
• ecological networks

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Lucille Billon is an ecologist specialized in geomatics. Her research concerns mapping green infrastructure, landscape ecology, spatial analysis, and the impact of roads on wildlife. She works at the UMS PatriNat (UMS 2006 on Natural Heritage, CNRS / MNHN / OFB), in charge of the implementation of the French Natural Heritage Inventory, in partnership with all the French biodiversity stakeholders, form researchers to decision-makers.

Cécile Duchêne is a senior researcher and lecturer at University Gustave Eiffel, IGN/ENSG (School for Engineers in GIScience), her research takes place in the LASTIG laboratory, MEIG team. She holds a PhD in computer science from University Pierre et Marie Curie (Paris 6) and an Habilitation in GIS from University Paris-Est. Her research interests are in automated spatial analysis, especially semantically enriching geographic features based on the analysis of their geometry; and automated cartography, especially automated cartographic generalization.

Sandrine Gomes was at the time of the work presented in this paper, students in geomatics at the school for engineers ‘ENSG-géomatique’.

Arnaud Grégoire was at the time of the work presented in this paper, students in geomatics at the school for engineers ‘ENSG-géomatique’.

Mathilde Kremp was at the time of the work presented in this paper, students in geomatics at the school for engineers ‘ENSG-géomatique’.

Sébastien Mustière is a senior researcher and lecturer at University Gustave Eiffel, IGN/ENSG (School for Engineers in GIScience), his research takes place in the LASTIG laboratory, MEIG team. He holds a PhD in computer science from University Pierre et Marie Curie (Paris 6) and an Habilitation in GIS from University Paris-Est. His research interests are in cartography and integration of heterogeneous geographical data.

Romain Sordello is an engineer specialized in landscape and biodiversity. He is an expert of ecological networks and habitat fragmentation at UMS PatriNat (UMS 2006 on Natural Heritage, CNRS / MNHN / OFB). His works have been contributing to green infrastructure policy in France for ten years.

Notes

1 In this study, only continental France is considered and the term ‘region’ refers to the former 21 administrative units (not including Corsica) because the data was collected prior to the 2016 regional reform that reduce the number of regions to 13.

2 Meadows, moorland, grass.

3 https://inpn.mnhn.fr/programme/trame-verte-et-bleue/carte-nationale?lg=en.