To date, there is no definitive approach to map snow depth in mountainous areas from spaceborne sensors. Here, we examine the potential of very-high-resolution (VHR) optical stereo satellites to this purpose. Two triplets of 0.70 m resolution images were acquired by the Pléiades satellite over an open alpine catchment (14.5 km²) under snow-free and snow-covered conditions. The open-source software Ame's Stereo Pipeline (ASP) was used to match the stereo pairs without ground control points to generate raw photogrammetric clouds and to convert them into high-resolution digital elevation models (DEMs) at 1, 2, and 4 m resolutions. The DEM differences (dDEMs) were computed after 3-D coregistration, including a correction of a −0.48 m vertical bias. The bias-corrected dDEM maps were compared to 451 snow-probe measurements. The results show a decimetric accuracy and precision in the Pléiades-derived snow depths. The median of the residuals is −0.16 m, with a standard deviation (SD) of 0.58 m at a pixel size of 2 m. We compared the 2 m Pléiades dDEM to a 2 m dDEM that was based on a winged unmanned aircraft vehicle (UAV) photogrammetric survey that was performed on the same winter date over a portion of the catchment (3.1 km²). The UAV-derived snow depth map exhibits the same patterns as the Pléiades-derived snow map, with a median of −0.11 m and a SD of 0.62 m when compared to the snow-probe measurements. The Pléiades images benefit from a very broad radiometric range (12 bits), allowing a high correlation success rate over the snow-covered areas. This study demonstrates the value of VHR stereo satellite imagery to map snow depth in remote mountainous areas even when no field data are available.

Little is known about the fluctuations of the Pyrenean glaciers. In this study, we reconstructed the evolution of Ossoue Glacier (42°46' N, 0.45 km2), which is located in the central Pyrenees, from the Little Ice Age (LIA) onwards. To do so, length, area, thickness, and mass changes in the glacier were generated from historical data sets, topographical surveys, glaciological measurements (2001–2013), a ground penetrating radar (GPR) survey (2006), and stereoscopic satellite images (2013). The glacier has receded considerably since the end of the LIA, losing 40 % of its length and 60 % of its area. Three periods of marked ice depletion were identified: 1850–1890, 1928–1950, and 1983–2013, as well as two short periods of stabilization: 1890–1894, 1905–1913, and a longer period of slight growth: 1950–1983; these agree with other Pyrenean glacier reconstructions (Maladeta, Coronas, Taillon glaciers). Pyrenean and Alpine glaciers exhibit similar multidecadal variations during the 20th century, with a stable period detected at the end of the 1970s and periods of ice depletion during the 1940s and since the 1980s. Ossoue Glacier fluctuations generally concur with climatic data (air temperature, precipitation, North Atlantic Oscillation, Atlantic Multidecadal Oscillation). Geodetic mass balance over 1983–2013 was −1.04 ± 0.06 w.e.a−1 (−31.3 ± 1.9 m w.e.), whereas glaciological mass balance was −1.45 ± 0.85 m w.e. a−1 (−17.3 ± 2.9 m w.e.) over 2001–2013, resulting in a doubling of the ablation rate in the last decade. In 2013 the maximum ice thickness was 59 ± 10.3 m. Assuming that the current ablation rate remains constant, Ossoue Glacier will disappear midway through the 21st century.

To date, there is no effective treatment to cure dengue fever, a mosquito-borne disease which has a major impact on human populations in tropical and sub-tropical regions. Although the characteristics of dengue infection are well known, factors associated with landscape are highly scale dependent in time and space, and therefore difficult to monitor. We propose here a mapping review based on 78 articles that study the relationships between landscape factors and urban dengue cases considering household, neighborhood and administrative levels. Landscape factors were retrieved from survey questionnaires, Geographic Information Systems (GIS), and remote sensing (RS) techniques. We structured these into groups composed of land cover, land use, and housing type and characteristics, as well as subgroups referring to construction material, urban typology, and infrastructure level. We mapped the co-occurrence networks associated with these factors, and analyzed their relevance according to a three-valued interpretation (positive, negative, non significant). From a methodological perspective, coupling RS and GIS techniques with field surveys including entomological observations should be systematically considered, as none digital land use or land cover variables appears to be an univocal determinant of dengue occurrences. Remote sensing urban mapping is however of interest to provide a geographical frame to distribute human population and movement in relation to their activities in the city, and as spatialized input variables for epidemiological and entomological models.

Greening cities is a nature-based strategy for sustainable urban development that integrates natural elements like plants or water bodies, to mitigate climate change impacts and enhance human well-being. However, urban green infrastructures (UGIs) can influence the distribution of disease vectors, potentially affecting vector-borne diseases (VBDs). UGIs may provide new suitable environments for urban vectors, while also creating opportunities to mitigate VBD risks through predation, competition, and dilution effects. This article examined the relationships between UGIs, vectors, and associated pathogens, impacting both human and animal health, highlighting knowledge gaps and identifying research priorities to support VBD risk mitigation measures and to guide smart urban planning and design.   A systematic literature search was conducted following PRISMA guidelines in three databases (Pubmed, Scopus, Web of Science). Selected articles involved (i) any aspect of a urban vector system, (ii) in UGIs, and (iii) statistical analysis of the effects of UGIs on VBD risk. Methods employed to characterize UGIs and VBDs were described and the identified impacts were summarized by vector group.   Among the 98 articles reviewed, most addressed mosquito-pathogen systems (66), tick-pathogen systems (29), and few other vector-borne pathogen systems (3), with studies often confined to a single city or several cities within the same country and focused on one vector group. Urban vegetation generally appeared to heighten the risk of tick-borne diseases. In contrast, the influence of UGIs on the risk of mosquito-borne diseases varied depending on the vector system and on the environmental and climatic context. The diversity of indicators used to assess UGIs and VBD risks may affect the observed impact on VBD risk.   Given the increasing popularity of urban greening, it is crucial to investigate its potential implications for public health, and thereby urban planning decisions. However, the lack of standardized protocols complicates the accurate assessment of the effects of UGIs on the risk for VBD emergence and transmission and consequently, on potential mitigation measures.

La distribution des moustiques vecteurs du paludisme est contrôlée par divers facteurs comme le climat, les types d’occupation du sol, ou les activités humaines. Dans la région amazonienne, des foyers endémiques de paludisme subsistent, notamment à la frontière entre la Guyane française et l’état d’Amapa au Brésil. Cette zone, longue de plus de 300 km, présente de nombreuses difficultés dans la collecte des informations nécessaires à la gestion sanitaire des populations présentes. Dans ce type de contexte géographique bénéficiant de peu de données, isolé et transfrontalier, une méthodologie fondée sur l’exploitation d’images de télédétection est particulièrement adaptée. Les données de télédétection présentent une large couverture spatiale, et une gamme importante de résolutions spatiales. Nous présentons ici une approche combinant des données satellite optiques et RADAR à haute et très haute résolution spatiale. Notre méthode permet de cartographier les différents types d’occupation du sol dans le contexte tropical frontalier Guyane française – Brésil, caractérisé par un fort ennuagement. Les résultats montrent que la complémentarité des capteurs optiques et RADAR permet de résoudre en grande partie la question de l’ennuagement persistant. En particulier, les classifications des différentes occupations du sol obtenues permettent de construire des indicateurs spatialisés en lien avec les espaces favorables à l’existence de gîtes larvaires et de zones de repos du vecteur du paludisme. A travers une discussion sur l’application de ces classifications composites à l’estimation du risque d’exposition vectoriel considéré à différentes échelles, ce cas d’étude illustre l'intérêt d’approches de télédétection satellite pour caractériser des éléments du paysage et l’occupation des sols, susceptibles de rendre compte de la distribution des populations vectorielles en lien avec la transmission d’arbovirus.

En prenant de la hauteur et en offrant une vue élargie des territoires, les images satellite et les photographies aériennes permettent d’appréhender les facteurs environnementaux qui peuvent conditionner la santé des populations. Depuis l’essor de la télédétection satellite à partir des années 1970, son usage dans le domaine de la santé a connu des succès modérés. Si son potentiel a été largement évoqué dans la littérature jusqu’aux années 2000, son apport opérationnel ne s’est pas imposé. Ce n’est que récemment que les applications en santé se sont enrichies et multipliées par le développement d’approches interdisciplinaires. Cet article vise à questionner les usages de la télédétection appliquée aux questions de santé selon les aspects techniques, historiques, et thématiques afin d’identifier les verrous. Il propose tout d’abord une vue didactique des principes théoriques, des données disponibles et des usages possibles. A travers une étude bibliographique, il offre un regard rétrospectif sur l’évolution de sa mise en œuvre dans le domaine la santé, qui permet de synthétiser les contributions actuelles : pour la cartographie opérationnelle, pour la surveillance et l’analyse des dynamiques des maladies infectieuses ou, dans une moindre de mesure, pour appréhender les vulnérabilités des populations comme les difficultés d’accès aux soins. Enfin, l’article conclut sur les limites, les recommandations et les perspectives pour optimiser ces usages dont les verrous sont souvent techniques et structurels mais pour lesquels des méthodologies doivent encore être développées.