Contribution de la télédétection à l’évaluation des fonctions des zones humides : de l’observation à la modélisation prospective

Interfacing between land and water systems, wetlands perform multiple functions and values that are now widely recognized. Inventory, delineation, but also characterization and monitoring of wetlands are now a priority to address the regression and in some cases the loss of these ecosystems. While wetland delineation is widely performed, the assessment of their functions has been only made on small sites of several hectares, whereas it is necessary to evaluate wetland functional status on larger areas to manage them. The objectives of this thesis are to develop a method to map wetland functions on areas greater than a hundred square kilometers, evaluate optical remote sensing data with very high spatial resolution to produce indicators of functional status of wetlands, and assess the impact of land use change on these functions. For this, the FAP approach has been adapted and applied to two sites located in Brittany and Dordogne. Once having defined and characterized wetlands from remotely sensed data, the spatial indicators derived from these data were used to evaluate hydrological, biogeochemical and ecological wetland functions. The evolution of these functions was then simulated under different scenarios of land use changes. The results show the usefulness of remotely sensed data, especially LiDAR data, to accurately characterize the micro-topography, drainage network and vegetation of wetlands. The functional potential of wetlands can therefore be mapped at different scales from the plot to the whole site for various functions. The simulation of land-use changes for the period 2000–2030 and the evaluation of their impact on wetland functions can be a tool for managing these environmentsLes zones humides, à l’interface entre terre et eau, sont des milieux riches et diversifiés, aux fonctions et valeurs multiples aujourd’hui largement reconnues. Face à la sensibilité grandissante des organisations gouvernementales, régionales et du public aux effets néfastes, directs ou indirects, de la régression, voire dans certains cas de la disparition des zones humides, l’inventaire, la délimitation, mais aussi la caractérisation et le suivi de ces milieux sont devenus une priorité. Si leur délimitation est aujourd’hui opérationnelle, l’évaluation de leurs fonctions n’a été opérée que sur des sites de quelques hectares, alors qu’il est nécessaire d’évaluer l’état fonctionnel des zones humides sur des territoires plus étendus pour les gérer. Les objectifs de cette thèse sont de développer une méthode permettant de spatialiser les fonctions des zones humides à l’échelle de territoires d’une centaine de Km² au minimum, d’évaluer des données de télédétection optiques à très haute résolution spatiale afin de produire des indicateurs de l’état fonctionnel des zones humides, et d’évaluer l’impact de changements d’occupation des sols sur ces fonctions. Pour cela, la démarche FAP a été adaptée et appliquée sur deux sites de 130 et 650 km² localisés en Bretagne et en Dordogne. Après avoir délimités et caractérisés les zones humides à partir de données de télédétection, des indicateurs spatialisés dérivés de ces données ont été utilisés pour évaluer des fonctions hydrologiques, biogéochimiques et écologiques. L’évolution de ces fonctions a ensuite été simulée selon différents scénarios de changements d’occupation des sols. Les résultats montrent l’intérêt des données de télédétection, en particulier LiDAR, pour caractériser avec précision la micro-topographie, le réseau hydrographique et la végétation des zones humides. Ces données permettent de cartographier le potentiel fonctionnel des zones humides à différentes échelles allant de la parcelle à l’ensemble du site, et ce pour différentes fonctions. La simulation des changements d’occupation des sols à l’horizon 2030 et l’évaluation de ceux-ci sur les fonctions des zones humides peuvent constituer un outil d’aide à la gestion de ces milieux

Evaluation des fonctions des zones humides à partir de données à très haute résolution spatiale. Application expérimentale à la basse vallée de la Dordogne.

rapport techniqueRapport Technique Epidor/CARE

Pouvoir comparer des états de conservation

National audienc

Using landscape metrics on satellite imagery to assess conservation status of Natura 2000 habitats

International audienceHow to assess conservation status of habitats, and particularly fl oristic diversity at landscape and community scales is still an outstanding issue. Here we propose a framework including remote sensing, calculation of landscape metrics and the use of diversity indicators to achieve this goal. The framework was tested for two consecutive years in meadows of the Loire valley (France). We demonstrated that meadow vegetation can be mapped at the community scale using per pixel supervised classifi cation based on ground truth phytosociological relevés applied onto multispectral imagery. Following the spectral variation hypothesis, we assessed fl oristic diversity at the landscape scale using a Shannon indexcalculated from the vegetation map produced (p Index). Consequently, mapping inter-annual variations of p Index allowed us to detect fl oristic diversity changes. We also demonstrated that some plant communities indicating a decrease of species diversity can be mapped using remotesensing. Thus, we were able to assess the inter- annual variations of species diversity at the community scale and we improved comprehensionof observed variations of species diversity at the landscape scale (p Index). Our framework represents a useful tool for managers, allowing them to assess and monitor plant species diversity at landscape and community scales over large areas

Mapping wetland functions using Earth observation data and multi-criteria analysis

International audienc

Using landscape metrics on satellite imagery to assess conservation status of Natura 2000 habitats

International audienceHow to assess conservation status of habitats, and particularly fl oristic diversity at landscape and community scales is still an outstanding issue. Here we propose a framework including remote sensing, calculation of landscape metrics and the use of diversity indicators to achieve this goal. The framework was tested for two consecutive years in meadows of the Loire valley (France). We demonstrated that meadow vegetation can be mapped at the community scale using per pixel supervised classifi cation based on ground truth phytosociological relevés applied onto multispectral imagery. Following the spectral variation hypothesis, we assessed fl oristic diversity at the landscape scale using a Shannon indexcalculated from the vegetation map produced (p Index). Consequently, mapping inter-annual variations of p Index allowed us to detect fl oristic diversity changes. We also demonstrated that some plant communities indicating a decrease of species diversity can be mapped using remotesensing. Thus, we were able to assess the inter- annual variations of species diversity at the community scale and we improved comprehensionof observed variations of species diversity at the landscape scale (p Index). Our framework represents a useful tool for managers, allowing them to assess and monitor plant species diversity at landscape and community scales over large areas

Habitat conservation status : scale, criteria and reference matter !

International audienc

Bioclimatic dataset of Metropolitan France under current conditions derived from the WorldClim model

International audienc

One year wetland survey investigations from quad-pol RADARSAT-2 time-series SAR images

International audienc

Dempster-Shafer Fusion Rule of Optical and Polarimetric Data for Winter Land Cover Mapping

International audienc