Search

International audience; Earth observation satellite imagery is increasingly accessible, and has become a key component for vegetation mapping and monitoring. Sentinel-2 satellites acquire optical images with five days' revisit frequency, which is an important feature to increase the probability of acquisition with reasonable cloud cover in tropical regions. Regular and reliable satellite observations open perspectives for the monitoring of vegetation properties and biodiversity. Atmospheric correction methods (ACMs) producing bottom-of-atmosphere (BOA) reflectance are critical to ensure temporal consistency of higher-level products and optimal sensitivity to changes in vegetation properties. Still their application in tropical regions remains challenging due to complex atmospheric issues. This study aims at performing ACM inter-comparison in the context of tropical forest monitoring. We produced BOA reflectance for a set of Sentinel-2 acquisitions corresponding to a forested area in Cameroon, using four atmospheric correction methods: Sen2cor, MAJA, Overland and LaSRC. We selected five successive acquisitions with moderate to no cloud cover, and computed a set of spectral indices and spectral diversity metrics in order to compare the consistency of these products through time, under the hypothesis that they should remain stable over a short period. We also assessed the agreement between atmospheric correction methods. Two spatial extents were used for the computation of spectral diversity metrics to assess the robustness of the data-driven processes applied to compute spectral diversity. We found that the choice of an ACM did have a significant impact on BOA reflectance and higher-level products. In the visible domain, Overland and LaSRC produced consistent BOA reflectance values, while MAJA and Sen2Cor showed strong variability which could not be explained by changes in surface properties. This directly influenced the temporal consistency of NDVI. Yet, the influence on the temporal consistency for EVI and NDWI was moderate. Spectral diversity metrics were consistent through time for all methods, but to a lesser degree than vegetation indices. When comparing the mean values over the period considered, vegetation indices were stable across methods, but not diversity metrics. Spatial context changes had an impact on the Shannon index, but not on Bray-Curtis dissimilarity. These results suggest that the choice of ACM has major potential implications for tropical forest monitoring.

The debate around the SARS-CoV-2 pandemic has raised multiple and incompletely answered questions regarding how zoonoses are transmitted from wild populations to humans, how they spread within human communities, over regions and across continents, how countries and societies can fight or counter pandemics and how landscapes will have to be effectively managed for limiting the spread of diseases keeping communities safe and healthy. info:eu-repo/semantics/publishedVersion

International audience; Monitoring the ecological status of natural habitats is crucial to the conservation process, as it enables the implementation of efficient conservation policies. Nowadays, it is increasingly possible to automate species identification, given the availability of very large image databases and state-of-the-art computational power which makes the training of automated machine learning-based classification models an increasingly viable tool for monitoring marine habitats. Coralligenous reefs are an underwater habitat of particular importance, found in the Mediterranean. This habitat is of a similar biocomplexity to coral reefs. They have been monitored in French waters since 2010 using manually annotated photo quadrats (RECOR monitoring network). Based on the large database of annotations accumulated therein, we have trained convolutional neural networks to automatically recognise coralligenous species using the data gathered from photo quadrats. Previous studies conducted on similar habitats performed well, but were only able to consider a limited number of classes, resulting in a very coarse description of these often-complex habitats. We therefore designed a custom network based on off-theshelf architectures which is able to discriminate between 61 classes with 72.59% accuracy. Our results showed that confusion errors were for the most part taxonomically coherent, showing accuracy performances of 84.47% when the task was simplified to 15 major categories, thereby outperforming the human accuracy previously recorded in a similar study. In light of this, we built a semi-automated tool to reject unsure results and reduce error risk, for when a higher level of accuracy is required. Finally, we used our model to assess the biodiversity and ecological status of coralligenous reefs with the Coralligenous Assemblage Index (CAI) and the Shannon Index. Our results showed that whilst the prediction of the CAI was only moderately accurate (pearson correlation between observed and predicted CAI = 0.61), the prediction of Shannon Index was more accurate (pearson correlation = 0.74). In conclusion, it will be argued that the approach outlined by this study offers a cost and time-effective tool for the analysis of coralligenous assemblages which is suitable for integration into a large-scale monitoring network of this habitat.

The quantitative characterization of landscape structure is critical to assess conservation, and monitor and manage biodiversity. The Mediterranean Basin is a biodiversity hotspot that illustrates the strong relationship between biodiversity and the complexity of the landscape mosaic. Our objective was to test the relevance of two textural indices and one radiometric index (the normalized difference vegetation index (NDVI)) to characterize vegetation structure. These indices could be used as indicators of vegetation composition and organization of four vertical strata when derived from airborne and Pl&eacute, iades space-borne VHSR imagery. More specifically, we analyzed the influence of the spatial resolution and the radiometric information on the characterization of the landscape structure. Our results indicated that NDVI information at 0.5 m spatial resolution was necessary to be able to incorporate the heterogeneity of vegetation structure. Indices derived from lower resolution NDVI images or different radiometric information than airborne images also proved to be sensitive to vegetation fragmentation and composition. NDVI images brought out details on ligneous/herbs patterns while panchromatic image brought out more details on herbs/bare soil patterns. Combined textural and NDVI indices show strong potential for vegetation structure understanding, allowing detailed mapping. NDVI information shows good potential for applications related to landscape closure dynamics, related habitat degradation indicators caused by shrub encroachment. Panchromatic derived information, on the other hand, provides information relevant in applications focusing grazing management.

The delimitation of bioregions helps to understand historical and ecological drivers of species distribution. In this work, we performed a network analysis of the spatial distribution patterns of plants in south of France (Languedoc-Roussillon and Provence-Alpes-C\^ote d'Azur) to analyze the biogeographical structure of the French Mediterranean flora at different scales. We used a network approach to identify and characterize biogeographical regions, based on a large database containing 2.5 million of geolocalized plant records corresponding to more than 3500 plant species. This methodology is performed following five steps, from the biogeographical bipartite network construction, to the identification of biogeographical regions under the form of spatial network communities, the analysis of their interactions and the identification of clusters of plant species based on the species contribution to the biogeographical regions. First, we identified two sub-networks that distinguish Mediterranean and temperate biota. Then, we separated eight statistically significant bioregions that present a complex spatial structure. Some of them are spatially well delimited, and match with particular geological entities. On the other hand fuzzy transitions arise between adjacent bioregions that share a common geological setting, but are spread along a climatic gradient. The proposed network approach illustrates the biogeographical structure of the flora in southern France, and provides precise insights into the relationships between bioregions. This approach sheds light on ecological drivers shaping the distribution of Mediterranean biota: the interplay between a climatic gradient and geological substrate shapes biodiversity patterns. Finally this work exemplifies why fragmented distributions are common in the Mediterranean region, isolating groups of species that share a similar eco-evolutionary history., Comment: 16 pages, 7 figures + Appendix

[Departement_IRSTEA]Territoires [TR1_IRSTEA]GEUSI [Axe_IRSTEA]TETIS-ATTOS [ADD1_IRSTEA]Dynamique et fonctionnement des écosystèmes; International audience; Underwater photogrammetry has been increasingly used to study and monitor the three-dimensional characteristics of marine habitats, despite a lack of knowledge on the quality and reliability of the reconstructions. More particularly, little attention has been paid to exploring and estimating the relative contribution of multiple acquisition parameters on the model resolution (distance between neighbor vertices), accuracy (closeness to true positions/measures) and precision (variability of positions/measures). On the other hand, some studies used expensive or cumbersome camera systems that can restrict the number of users of this technology for the monitoring of marine habitats. This study aimed at developing a simple and cost-effective protocol able to produce accurate and reproducible high-resolution models. Precisely, the effect of the camera system, flying elevation, camera orientation and number of images on the resolution and accuracy of marine habitat reconstructions was tested through two experiments. A first experiment allowed for testing all combinations of acquisition parameters through the building of 192 models of the same 36 m(2) study site. The flying elevation and camera system strongly affected the model resolution, while the photo density mostly affected bundle adjustment accuracy and total processing time. The camera orientation, in turn, mostly affected the reprojection error. The best combination of parameters was used in a second experiment to assess the accuracy and precision of the resulting reconstructions. The average model resolution was 3.4 mm, and despite a decreasing precision in the positioning of markers with distance to the model center (0.33, 0.27, and 1.2 mm/m Standard Deviation (SD) in X, Y, Z, respectively), the measures were very accurate and precise: 0.08% error +/- 0.06 SD for bar lengths, 0.36% +/- 0.51 SD for a rock model area and 0.92% +/- 0.54 SD for its volume. The 3D geometry of the rock only differed by 1.2 mm +/- 0.8 SD from the ultra-high resolution in-air reference. These results suggest that this simple and cost-effective protocol produces accurate and reproducible models that are suitable for the study and monitoring of marine habitats at a small reef scale.

International audience; The Mediterranean forests have been used for millennia and are organized according to a heterogeneous and complex landscape particularly beneficial to biological diversity. The forests have been degraded by overgrazing and exploitation for firewood, but also as a result of fires. Such forest areas may become open, secondary forests with several understories, but if not properly managed they may turn into varied types of high or low matorral (dry shrubland) or in some areas to heathlands that could be degraded into sparsely vegetated areas. As a result, there is an urgent need for monitoring tools to inform changes in this valuable ecosystem to support public policies to protect a sustainable management of these biodiversity hotspots. In the framework of the Essential Biodiversity Variables (EBV) developed by the GEO-BON, six classes of variables have been defined to cover different key indicators, including ecosystem structure, which is intimately linked to the fauna and flora richness. Remotely-sensed earth observation (RS) has become essential to provide a rapid, repeated and synoptic access of these EBVs (i.e., RS-enabled EBVs): the increasing availability of open access satellite data provides enhanced possibilities to monitor this natural landscape under increasing anthropic pressures. Mediterranean ecosystem could be monitor with various types of sensors, providing information on key indicators like structure, function and composition at frequent revisit times and high to very high spatial resolution. The support of innovative descriptors involving tools such as light sensors embedded on drones, spectro-radiometers or terrestrial Lidar are also needed.

International audience; Landscape heterogeneity is a key factor for understanding ecosystems function and is often associated to high biodiversity. Yet, its characterization for biodiversity monitoring still remains challenging, especially for very heterogeneous landscapes mosaics. In this work, we study the potential of Fourier-based Textural Ordination (FOTO) applied on high resolution airborne optical images to provide synthetic information about landscape fragmentation of Mediterranean heterogeneous landscapes. The ability of texture indices resulting from FOTO combined with vegetation indices to predict landscape metrics was also tested using non linear SVM regression. Our research showed that FOTO methods had great potential to finely characterize different vegetation strata organization at large scale with only few synthetic indices. Best regression results were obtained for ligneous and ground strata fragmentation with coefficient of determination greater than 0.7.

International audience; In environmental valuation, although it is well recognised that the choice of method heavily affects the outcome, little is known on how existing valuation methods actually elicit the different values. Through the assessment of real-life applications of valuation of nature, this study tracks down the suitability of 21 valuation methods for 11 value types and assesses the methodological requirements for their operationalization. We found that different valuation methods have different suitabilities to elicit diverse value-types. Some methods are more specialized than others, but every method has blind spots, which implies risks of biased decision-making. We summarized different value-types according to three value dimensions: non-anthropocentric, relational and instrumental. No single valuation method is able to capture this full spectrum of values of nature. Covering all value dimensions requires careful selection of complementary valuation methods. This study also demonstrates that performing such an integrated valuation does not necessarily entail more resources, as for every value dimension, methods with low to medium operational requirements are available. With this study, we aim to provide guidance for selecting a complementary set of valuation methods in order to develop integrated valuation in practice that includes values of all stakeholders into environmental decision-making. In special issue synthesizing OpenNESS.

International audience; This special issue (SI) is primarily composed of 12 papers generated from a selection of contributions from two main events. The first event was the biannual conference organized by the International Union of Forest Research Organizations (IUFRO) Working Party (Division 8): Forest Landscape Ecology, held in Tartu (Estonia) in 2015, under the theme 'Sustaining Ecosystem Services in Forested Landscapes'. The second event was a symposium organized during the Ecosummit in Montpellier (France) in 2016 under the theme Ecological Sustainability: Engineering Change. The symposium was a joint effort from the EU-funded OpenNESS project, IALE and IUFRO communities, under the theme 'Scenarios and models of key indirect and direct drivers in relation to nature's benefits to people'. These two events have a common ground addressing the use of ecosystem services (ES) in planning and policymaking at different scales. Although the focus of the events, and of this SI, is multi-sectoral, emphasis is given on integrative multifunctional landscape management approaches, with examples mainly from forested landscapes. Besides, this common effort integrates important inputs from the forest cluster of the EU-OpenNESS project (Operationalization of natural capital and ecosystem services) that also participated in the symposia and exchange of ideas and approaches.

International audience; The ecosystem service (ES) concept is acknowledged for its potential to support decision-making on various scales. Still, it lacks in practical implementation, particularly concerning spatial planning and land management - key aspects that lead to criticism in its applicability. ES in planning and decision-making can contribute to improve the quality of land use and management by integrating synergies, trade-offs and conflicts among economy, environment and societal goals. This opinion paper suggests a nexus approach that shows how ES can contribute to characterize the interactions between humans and nature on different temporal and spatial scales while integrating cross-scale effects in trade-off analyses. We discuss how our nexus approach can be implemented and contribute to revealing the interdependencies between policy sectors, spatial and land-use planning. We argue that thinking in terms of a nexus adds to an improved coherence across different policy sectors relevant for spatial planning. We conclude that only a strategic and concise use of ES throughout all decision levels will help to create maximum benefits for harmonizing policy, planning and management instruments supported by intervention measures for the sake of sustainable development. In Special Issue on Ecosystem Services Nexus Thinking.

International audience; An integrated methodology, based on linking Bayesian belief networks (BBN) with GIS, is proposed for combining available evidence to help forest managers evaluate implications and trade-offs between forest production and conservation measures to preserve biodiversity in forested habitats. A Bayesian belief network is a probabilistic graphical model that represents variables and their dependencies through specifying probabilistic relationships. In spatially explicit decision problems where it is difficult to choose appropriate combinations of interventions, the proposed integration of a BBN with GIS helped to facilitate shared understanding of the human-landscape relationships, while fostering collective management that can be incorporated into landscape planning processes. Trades-offs become more and more relevant in these landscape contexts where the participation of many and varied stakeholder groups is indispensable. With these challenges in mind, our integrated approach incorporates GIS-based data with expert knowledge to consider two different land use interests - biodiversity value for conservation and timber production potential - with the focus on a complex mountain landscape in the French Alps. The spatial models produced provided different alternatives of suitable sites that can be used by policy makers in order to support conservation priorities while addressing management options. The approach provided provide a common reasoning language among different experts from different backgrounds while helped to identify spatially explicit conflictive areas.

International audience; In response to extensive criticism of the monetary valuation of ecosystem services deliberative monetary valuation (DMV) has been proposed as an improved approach that combines the benefits of deliberative decision-making with the advantages of monetary values. In this study the body of literature that has developed in the field of deliberative monetary valuation is reviewed to assess the potential advantages and challenges that this approach can bring to the valuation of ecosystem services. The studies reviewed present a range of approaches to DMV based on different paradigms and methods. While studies that implemented DMV were primarily concerned with improving monetary values within the neoclassical economic paradigm, proposals for DMV in theoretical papers are challenging this paradigm and stress the potential for DMV to produce more democratic and equitable values. It was found that DMV still faces large practical and theoretical challenges, most notably the lack of a theoretical base for the interpretation of the monetary values produced. Before these challenges are addressed it is early days to assess the usefulness of DMV for the valuation of ecosystem services.

International audience; & Context Uneven-aged management systems based on selec-tion silviculture have become popular in European mountain forests and progressively replace other silvicultural practices. In time, this trend could lead to a homogenisation of the forest mosaic with consequences on structural indices recognised as beneficial to forest biodiversity. & Aims This study was conducted to investigate the potential effects of a generalisation of the selection silvicultural system on structural diversity in the forest landscape with conse-quences for forest biodiversity conservation. & Methods We compared four structural indices (tree species richness, diameter heterogeneity, deadwood volume and basal area of mature trees) in five different stand types typical of the northern French Alps, using forest plot data in the Vercors mountain range. Through virtual landscape simulations, we then calculated predicted mean proportions of stand types under two different conservation strategies: (i) maximising mean index values at the landscape level and (ii) maximising the number of plots in the landscape with index values above given thresholds. & Results Multi-staged forests did not maximise all indices, the best solution being to combine the five stand types in uneven proportions to improve biodiversity conservation. & Conclusion The expansion of selection silviculture in Euro-pean heterogeneous forest landscapes could enhance biodi-versity conservation if other stand types with complementary structural characteristics are maintained.

International audience; Contemporary landscape ecology continues to explore the causes and consequences of landscape heterogeneity across a range of scales, and demands for the scientific underpinnings of landscape planning and management still remains high. The spatial distribution of resources can be a key element in determining habitat quality, and that in turn is directly related to the level of heterogeneity in the system. In this sense, forest habitat mosaics may be more affected by lack of heterogeneity than by structural fragmentation. Nonetheless, increasing spatial heterogeneity at a given spatial scale can also decrease habitat patch size, with potential negative consequences for specialist species. Such dual effect may lead to hump-backed shape relationships between species diversity and heterogeneity, leading to three related assumptions: (i) at low levels of heterogeneity, an increase in heterogeneity favours local and regional species richness, (ii) there is an optimum heterogeneity level at which a maximum number of species is reached, (iii) further increase in spatial heterogeneity has a negative effect on local and regional species richness, due to increasing adverse effects of habitat fragmentation. In this study, we investigated the existence of a hump-shaped relationship between local plant species richness and increasing forest landscape heterogeneity on a complex mosaic in the French Alps. Forest landscape heterogeneity was quantified with five independent criteria. We found significant quadratic relationships between local forest species richness and two heterogeneity criteria indicators, showing a slight decrease of forest species richness at very high heterogeneity levels. Species richness–landscape heterogeneity relationships varied according to the heterogeneity metrics involved and the type of species richness considered. Our results support the assumption that intermediate levels of heterogeneity may support more species than very high levels of heterogeneity, although we were not able to conclude for a systematic negative effect of very high levels of heterogeneity on local plant species richness.

La connectivité du paysage est reconnue comme l’un des éléments fondamentaux pour la gestion et la conservation durable de la biodiversité et des écosystèmes. L’état de connectivité du paysage définit le degré de facilité avec lequel les espèces se dispersent entre leurs habitats. La combinaison de modèles de distribution et de connectivité basés sur la théorie des graphes permet de produire des outils spatialisés illustrant l’état de connectivité d’un paysage donné. Cette méthode renseigne sur l’importance relative des n½uds d’habitats et des corridors. Au sein de l’équipe de modélisateurs d’Irstea Grenoble et avec le soutien d’experts naturalistes de l’Office national des forêts (ONF) et des Ligues pour la protection des oiseaux (LPO) de la Drôme et de l’Isère, une analyse de connectivité a pu être mise en ½uvre sur deux espèces de chauves-souris dans le massif du Vercors. Cette étude s’est déroulée dans le cadre du projet MocHab (" Modélisation de la distribution des espèces : un outil pour l’évaluation, la conservation des habitats d’espèces et des continuités écologiques ") financé par le ministère de l’Écologie, du Développement durable et de l’Énergie (MEDDE). / Landscape connectivity is considered as a key issue for biodiversity conservation and natural ecosystems stability. Hence, landscape connectivity defines the degree to which the landscape facilitates or impedes movement among resource patches. Habitat modelling coupled with connectivity analysis based on graph theory provides a spatial operational approach to an integrative landscape management. The approach provides maps showing the connectivity status of different patches within the landscape matrix. The project was carried out in France by the Landscape ecology modelling group working at Irstea Grenoble in tandem with natural experts from the National Forest Office (ONF) and Bird Protection Leagues (LPO) from Drôme and Isère Departments. Two species of wild horseshoe bats were studied on regional natural park of Vercors. The work is a part of MocHab project (“Modeling of species distribution: a tool for habitat evaluation and conservation as well as ecological connectivity”). It was financed by the French Ministry of Ecology, Sustainable Development and Energy (MEDDE).

International audience; Landscape structure is a key factor for biodiversity conservation. We assessed the potential role of landscaperelated habitat structure on Hazel Grouse (Tetrastesbonasia) by recording the occurrence of the species. Hazel Grouse is a widely recognized endangered species, because of the habitat loss as a direct consequence of land use change that is jeopardizing the species survival. The aim of this study is to provide a method based on habitat suitability modelling to explore and analyse hazel grouse- landscape structure and its relation to key habitat features. We evaluated landscape factors and critical threshold for monitoring the species, in order to assess the predictive power of models based on field surveys, ancillary information and high resolution infrared aerial photographs. We tested Maximum Entropy (MaxEnt) algorithm, in order to predict the distribution of Hazel Grouse species, in the complex mountain landscape within the study site. This presence-only modelling method has showed numerous advantages over many other approaches. It is based on a function that links the fitness of individuals to their environment. Our results were highly consistent with field knowledge, showing that habitat modelling generated using spatial statistics and GIS can effectively help in the characterization of habitat requirements and the localization of the species suitable habitat. We found also that key drivers of Hazel Grouse distribution are not only environmental factors, in particular linked to elevation in mountain areas, but also landscape heterogeneity is a key feature. Hence, conservation of this species will require land management practices that maintain heterogeneous landscape; in particular small forest openings are essential for the species. The approach developed seem to be a promising operational tool for local and regional managers interested in species monitoring and management within the long term.

Landscape connectivity is a multi-scalar concept allowing the investigation of how the interaction between species movement abilities and landscape structure affects species survival, gene flow and other key ecological processes in fragmented landscapes. This requires the determination of functional connectivity which is the end result of a complex combination of multiple factors such as habitat amount and arrangement, matrix quality and permeability, species perceptions and dispersal behaviour, population density, etc. Functional connectivity quantification necessitates also the consideration of the impacts and constraints imposed by the increasing rates of landscape and environmental change, which are ultimately driven by socioeconomic factors and are likely to continue putting more pressures on both managed and natural landscapes. Connectivity is nowadays an important concern in almost any modern conservation plan around the globe. The challenge of these conservation plans is to identify the spatial scale(s) and key landscape elements needed to maintain or restore connectivity and the ecological processes that are promoted by it. To meet the final objective of favouring species viability and ecosystem diversity, landscape ecologists should be able to deliver conservation guidelines and indicators at the spatial scale at which the impacts of landscape change are most prominently affecting the abundance and persistence of the focal species. They also need to convincingly demonstrate the effectiveness and benefits of connectivity investments compared to other competing conservation alternatives. In this context, integrated approaches offering synergies and new capabilities for connectivity conservation planning should allow us to interpret the effects of landscape spatial heterogeneity and to define critical threshold levels at which landscapes are connected allowing the persistence of species (Opdam et al. 2003). The series of papers in this special issue constitute a valuable addition towards this end, by showing how a diversity of analytical approaches and data types can be applied, and in many case combined in an integrated fashion, in order to address various aspects that are at play while quantifying landscape connectivity and to support related management decisions. The contributions from this special issue include (i) empirical assessments of the role of different connectivity-related S. Luque (&) Cemagref, Institute for Agricultural and Environmental Engineering Research, Mountain Ecosystems Research Unit, 2 Rue de la Papeterie, 38402 Saint-Martin d’Heres, France e-mail: sandra.luque@irstea.fr; sandra.luque@cemagref.fr

The present loss of species and genetic diversity decreases the resilience of ecosystems, while at the same time ecosystems experience growing pressures from drivers such as climate change and land use change. The challenge is to translate these threats to biodiversity into tangible and quantifiable factors which can be used by policymakers to promote the development of flexible and effective conservation strategies (Harrison 2008). Increasing knowledge and awareness of the goods and services provided by ecosystems, and the importance of conserving them for maintaining our own quality of life, aims to address this challenge. Ecosystem goods and services and their continued delivery are essential to our economic prosperity and well-being (Millennium Ecosystem Assessment 2005). Modifications of ecosystems to enhance one service generally have come at a cost to other services due to trade-offs. Since changes in the quantity or quality of various types of natural resources and ecosystem services have large impact on human welfare and competitiveness of an economy, comprehensive methods to measure and value biodiversity and ecosystem services are needed to mitigate global change.

International audience; Selecting reserves for forest biodiversity maintenance is often done by setting criteria for components of structural elements of biodiversity, such as a volume of decaying wood. We tested how the different threshold values for the components of structural elements affect the cost-effective site selection. Using Finnish National Forest Inventory information and remote sensing data, we determined a habitat quality index and economic value for each site in Satakunta region in Finland. Moreover, we defined several sets of potential conservation targets using alternative criteria for the habitat quality index developed for the Finnish case study. These figures were used in the site selection model in order to maximize the sum of habitat index of selected areas under a given budget constraint. We found that the production possibility frontier for the outputs of timber and biodiversity is only slightly concave when using the given threshold values. Thus, the optimal combination of the outputs is sensitive to the relative values of these goods. Our results suggest that an integrated approach in forest conservation could provide to environmental managers considerable cost savings compared with current management practices. Environmental managers could also reduce conservation costs by loosening the criteria for potential conservation targets. This would not lower considerably the quality of conserved forests.

International audience; Biodiversity issues have gained importance in forestry as a result of the increased awareness of forest landscape changes, but still there is much to do before forest management meets reasonable goals for forest protection and renewal of biodiversity. In this work, we focus on boreal forest landscapes, using Finland as a case study, and taking advantage of a valuable database -the National Forest Inventory (NFI). We explore a multicriteria approach by using a predictive habitat suitability model for three-toed woodpecker (Picoides tridactylus) based on Weights of Evidence (WofE) and a combination of remote sensing and field data derived from the Multisource Finnish National Forest Inventory (MS-NFI). The WofE model is a quantitative method used for combining evidence to examine the support for a given hypothesis. WofE involves the estimation of a response variable (favourability for certain habitat occurrence) and a set of predictor variables (e.g. GIS layers containing environmental variables). WofE is based on a log-linear form of Bayes' rule and uses the prior probability distribution and the likelihood of the data to generate a posterior probability distribution. Very few examples exist of WofE being used to predict the spatial distribution of species or communities using biophysical descriptors. This work explores WofE as a tool for rapid biodiversity assessment using georeferenced species information. Since the method is dependent of the indicator species used as a surrogate of biodiversity value it can be applied for assessing biodiversity conditions of both managed and protected areas to help decision-making concerning protection of valuable habitats. Thus, the map of habitat suitability, represented as a range of probabilities of occurrence, offers an objective framework for evaluating the outcomes of different scenarios. Similarly, an objective assessment of habitat suitability provides a rational basis for management decisions incorporating impact on species habitat.

The preservation of biodiversity is a priority issue, both at national, European and international levels. In order to provide a better understanding of ecosystem functioning, spatial heterogeneity of natural environments is becoming one of the key components for the study of biodiversity. The Mediterranean basin is a hotspot of biodiversity for which the synergies between biodiversity and spatial heterogeneity of landscapes are particularly important. Mediterranean environments are organized into heterogeneous mosaics of four vertical strata~: bare soil, herbs, low ligneous and high ligneous. The biodiversity of these unique hotspots is now threatened by a closure of the landscape that leads to the habitat loss and landscape homogenization. The loss of heterogeneity is also leading to an increase in fire risks.This thesis aims to develop indices characterizing the spatial heterogeneity of natural landscapes in a Mediterranean context using very high spatial resolution remote sensing images. Among the various methods dedicated to the characterization of heterogeneity, the FOTO (FOurier Based Textural Ordination) method is particularly relevant because it produces uncorrelated texture gradients in an unsupervised manner, allowing continuous variations in spatial heterogeneity to be characterized at different spatial scales. Thus, the first objective of this thesis is to test the potential of texture indices derived from the FOTO method for the characterization of spatial heterogeneity relative to four vertical strata. The second objective is to test the sensitivity of our approach to technical and environmental factors, in order to ensure its replicability, and promote its use in an operational context of monitoring Mediterranean environments. Finally, based on a case study centered on the spatial distribution of bird species sensitive to vegetation heterogeneity, the last objective is oriented towards the validation of the ecological relevance of the heterogeneity indices.Combined with a vegetation index, NDVI, the texture indices derived from the FOTO method could be interpreted in terms of spatial heterogeneity and make it possible to characterize the composition and organization of the four vertical strata studied. These indices are influenced bymultiple factors, including the anthropization of landscapes showing patterns translated into surfaces such as crops, and the nature of the radiometric information of the remote sensing images processed. This pattern information impacts the apparent contrast of vegetation strata. Thus, the application of the method on a panchromatic band is more sensitive to patterns related to the alternation of bare soil and herbs while the application of the method on NDVI is more sensitive to patterns related to the alternation of ligneous strata with the herbaceous stratum. Finally, we have shown the interest of the approach developed for the prediction of several bird species with high conservation stakes. Heterogeneity indices have made it possible to highlight vegetation structures that are particularly favourable to certain bird species.The approach developed in this thesis is particularly stimulating because it allows the unsupervised production of three complementary indices characterizing several components of spatial heterogeneity related to four strata. Further efforts are needed to improve i) our understanding of the contribution of environmental and instrumental factors to the stability of the approach and ii) its automation for application in an operational context for mapping and monitoring the conservation status of natural habitats and birdlife.; La préservation de la biodiversité est un enjeu prioritaire, identifié aussi bien au niveau national qu’au niveau européen et international. L’hétérogénéité spatiale des milieux naturels est l’une des composantes clefs pour l’étude de la biodiversité et permet de comprendre le fonctionnement des écosystèmes. Le bassin Méditerranéen est un hotspot de biodiversité pour lequel le lien entre biodiversité et hétérogénéité spatiale des paysages s’illustre particulièrement bien. Les milieux méditerranéens s'organisent en mosaïques hétérogènes de quatre strates verticales: le sol nu, l’herbe, les ligneux bas et les ligneux hauts. La biodiversité de ces milieux est aujourd'hui menacée par une fermeture de milieux naturels qui entraîne la disparition de certains habitats et l’homogénéisation des paysages, homogénéisation qui entraîne elle-même une augmentation des risques d’incendies.Cette thèse se propose de développer des indices caractérisant l’hétérogénéité spatiale des milieux naturels dans un contexte méditerranéen à partir d’images de télédétection à très haute résolution. Parmi les différentes méthodes permettant de caractériser l'hétérogénéité, la méthode FOTO (FOurier Based Textural Ordination) est particulièrement intéressante car elle produit de façon non supervisée un nombre limité de gradients de texture non corrélés, à partir desquels il est possible de décrire les variations continues de l’hétérogénéité spatiale, et ce, à plusieurs échelles spatiales. Ainsi le premier objectif de cette thèse est de tester le potentiel des gradients de texture issus de la méthode FOTO pour la caractérisation de l’hétérogénéité spatiale relative aux quatre strates verticales caractéristiques des milieux méditerranéens. Le deuxième objectif est de tester la sensibilité de l’approche développée à des facteurs techniques et environnementaux, afin de s’assurer de sa réplicabilité pour favoriser son utilisation dans un contexte opérationnel de suivi des milieux méditerranéens. Enfin, le dernier objectif est de valider la pertinence écologique des indices d’hétérogénéité développés à travers un cas d’application~: la caractérisation de la répartition spatiale d’espèces d’oiseaux sensibles à l’hétérogénéité de la végétation.Combinés avec un indice de végétation, le NDVI, les indices de texture issus de la méthode FOTO ont pu être interprétés en termes d'hétérogénéité spatiale et ont permis de caractériser la composition et l'organisation des quatre strates verticales étudiées. Ces indices sont influencés par la présence de surfaces anthropisées comme les cultures ainsi que par la nature de l'information radiométrique des images de télédétection utilisées, qui impacte le contraste apparent des strates de végétation. Ainsi, l'application de la méthode sur une bande panchromatique est plus sensible aux motifs liés à l'alternance de sol nu et d'herbe tandis que l'application de la méthode sur le NDVI est plus sensible aux motifs lié à l'alternance des ligneux avec la strate herbacée. Enfin, nous avons montré l’intérêt de l’approche développée pour la prédiction de plusieurs espèces d’oiseaux à fort enjeux de conservation. Les indices d’hétérogénéité ont permis de mettre en évidence des structures de la végétation particulièrement favorables à certaines espèces d’oiseaux.L'approche développée dans cette thèse est particulièrement intéressante car elle permet la production non supervisée de trois indices complémentaires caractérisant plusieurs composantes de l'hétérogénéité spatiale relatives à quatre strates. Des efforts sont encore nécessaires pour améliorer i) notre compréhension de la contribution de facteurs environnementaux et instrumentaux sur la stabilité de l'approche et ii) son automatisation en vue d'une application dans un contexte opérationnel pour la cartographie et le suivi de l'état de conservation des habitats naturels et de l'avifaune.

In the context of global change and current loss of biodiversity, there is an urgent need to improve spatial approaches for assessing and monitoring biodiversity in order to develop a conceptual framework based on biological indicators that can be used in conservation planning. The problem still remains in terms of decisions and knowledge on where to set appropriate conservation targets. Hence, we need detailed and reliable information about forest landscape structure and composition and methods for estimating this information over the whole spatial domain. This work is based on an approach involving conservation of a patrimonial species in a mountain landscape. The Regional Natural Park in the French sub-Alps, used for this study encounters multiple conflicts (i.e. ecological, economic, tourism pressures). The stakeholders are then very concern on "where to manage" in other words, they need tools to define the perimeter of good quality habitat to optimize management at an optimal scale. Landscape metrics are widely used to explore the spatial heterogeneity of landscapes that influence several species distribution. Few empirical researches have comparatively examined their indicator value for certain species occurrence at different scales. Within the framework of this study we test hypothesis concerning the best scale at which Hazel Grouse respond to the landscape structure. Our aim was to evaluate significant relations between different landscape level indicators and species occurrence and to assess the effects of the extent of the considered landscape on their performance. Results showed that spatial scale affected the performance of the metrics, since Hazel Grouse occurrence was usually better predicted at relatively smaller extents of surrounding landscape. In all, outputs of this work constitute support for forest management, as they provide a methodological framework and indicators for prioritizing areas in terms of habitat quality where species conservation planning can be optimized., Dans le contexte du changement global et de la perte de la biodiversité, la prise en compte de cette dernière dans la gestion forestière reste encore très générale. Les démarches ne sont pas encore opérationnelles alors que les gestionnaires ont besoin d'outils destinés directement à la planification. Ainsi, il est devenu urgent d'améliorer les approches d'évaluation et de suivi de la biodiversité et de développer un cadre conceptuel à partir des indicateurs biologiques qui puisse servir dans la prise des décisions. Ce travail se repose sur une approche associant l'enjeu de conservation d'une espèce sauvage patrimoniale dans un paysage de montagne à la maîtrise d'une gestion forestière qui détermine la qualité de son habitat. Dans le cadre concret de la gestion forestière d'un Parc Naturel Régional où les enjeux sont multiples (écologiques, économiques, touristiques), les acteurs concernés s'interrogent moins sur le « comment gérer » que sur le « où gérer » ; en d'autres termes, définir les périmètres de bonne qualité d'habitat afin d'optimiser la gestion et à l'échelle optimale. Notre travail est moins de procurer des outils aux gestionnaires que de poser les jalons scientifiques d'une approche holistique inspirée de l'écologie du paysage. Nous partons ainsi de l'hypothèse selon laquelle les variables environnementales ainsi que la structure du paysage influencent la présence d'une espèce indicatrice de la diversité biologique d'un milieu. Dans ce travail nous nous appuyons sur cette hypothèse pour développer une démarche spatialement explicite qui permettrait d'atteindre l'objectif de conservation dans le cadre d'un processus de gestion forestière adaptative, en étudiant le cas de la gélinotte des bois dans le Parc Naturel Régional de Grande Chartreuse. Ce modèle prédictif de l'occurrence de la gélinotte des bois en Chartreuse s'appuie sur des indicateurs environnementaux et paysagers aisément mesurables et spatialisables. Ceci permettra d'établir un diagnostic de la qualité de l'habitat, d'approfondir les connaissances sur les relations entre la structure du paysage et l'espèce à différentes échelles et de déterminer les secteurs d'habitat qui sont les plus appropriés à la gélinotte des bois en zone de montagne. La représentation spatiale de l'hétérogénéité à différentes échelles permet d'envisager de nombreuses applications dans les domaines de la conservation et de la gestion forestière multifonctionnelle. Nos résultats, relevant d'une approche spatialement explicite, valident l'hypothèse selon laquelle la qualité de l'habitat de la gélinotte peut être modélisée avec une précision acceptable uniquement à partir d'indices paysagers, s'ils sont calculés sur la bonne étendue. Ils constituent donc une avancée pour une aide à la gestion, puisqu'ils préfigurent d'un outil permettant la localisation de zones prioritaires sur lesquelles la conservation de la gélinotte peut être optimisée.

There is a general consensus that as pressures on natural resources increase, biodiversity is being lost, and the rate of loss is not sustainable. Within the present situation is become a critical need to develop methods and tools for biodiversity monitoring and conservation. In particular, we need spatially-explicit tools and rapid assessment methods that are relatively easy to implement at different scales and at a relatively low cost. One of the basic assumptions in ecology is that there are positive relationships at different spatial scales between landscape heterogeneity and species richness in a given landscape mosaic. In this thesis, we focus on this assumption in order to build a Potential Species Biodiversity Index. Our aim was to assess potential biodiversity within a forest landscape mosaic, considering the Vercors' mountain range as a case study. The index encompasses indirect biodiversity indicators and criteria as a surrogate to biodiversity potential present for a given area. This approach allows a better understanding of the relationships between forests stand structure, forest landscape characteristics and species richness or geographical distribution. The main steps of the method and its evaluation are presented in scientific papers. The analysis of geographical distribution of the index at different spatial scales provides practical applications for conservation planning and multifunctional forest management related fields., Le déclin de la biodiversité lié à l'augmentation des pressions sur les ressources naturelles, fait l'objet d'un large consensus. Cette situation souligne un besoin urgent de développer des outils de diagnostic et de suivi de l'état de la biodiversité qui soient spatialisés, rapides à mettre en œuvre, peu coûteux et qui permettent de réaliser des expertises à l'échelle des territoires. Une des hypothèses centrales en écologie est qu'il existe des relations positives entre l'hétérogénéité spatiale mesurée dans la mosaïque paysagère et la richesse en espèces qui peut y cohabiter à différentes échelles. Dans ce travail, nous nous appuyons sur cette hypothèse pour développer un Indice de Biodiversité Spécifique Potentielle afin de réaliser un diagnostic de l'état de la biodiversité dans la mosaïque paysagère intra-forestière à différentes échelles, en prenant l'exemple du massif du Vercors. Cet indice s'appuie sur des indicateurs et des critères capables de refléter le niveau de biodiversité potentiellement présente dans une zone géographique donnée, et permet d'approfondir les connaissances sur les relations entre la structure des peuplements, les caractéristiques de la mosaïque forestière et la richesse ou la répartition géographique des espèces. Les étapes clés de la méthodologie et de son évaluation sont valorisées sous forme d'articles. La représentation spatiale de la biodiversité potentielle à différentes échelles permet d'envisager de nombreuses applications dans les domaines de la conservation et de la gestion forestière multifonctionnelle.