Portail "HAL-Francophonie Afrique et Océan Indien"
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Le tilapia, un poisson dont le succès pose question, des Caraïbes au Pacifique
No full texthttps://theconversation.com/le-tilapia-un-poisson-dont-le-succes-pose-question-des-cara-bes-au-pacifique-265895Entre promesse de résilience alimentaire et menaces écologiques silencieuses, le tilapia cristallise aujourd’hui les grands enjeux du développement de l’élevage de poissons dans les territoires insulaires. En Haïti par exemple, où il s’est largement développé, le tilapia est présenté comme une solution prometteuse pour renforcer la sécurité alimentaire. Toutefois, cette expansion, souvent promue sans garde-fous écologiques solides, soulève de vives préoccupations environnementales, notamment autour de la gestion de l’eau douce et des risques liés à la diffusion incontrôlée du tilapia dans les milieux naturels
Analyzing the miraculin content of Beninese Sisrè berries (Synsepalum dulcificum Schumach. & Thonn.) and exploring its thermal behavior
No full textInternational audienceThe pulp of the miracle fruit (Synsepalum dulcificum) has the ability to change the acidic taste of ingested foods into a sweet taste. This functionality is due to miraculin, a glycoprotein presents in the pulp of the fruit. Miraculin is low in calories and can be used for the development of stabilized natural sweetener for food. This study aimed to extract and quantify the miraculin level in the pulp of Sisrè (Synsepalum dulcificum) collected from various localities of Benin and explore its thermal behavior. The aim was to generate preliminary quantitative data on the termosensitivity of miraculin. The beninese miracle fruits were characterized by an average mass value of 0.9 g, a length of 1.66 cm and a thickness of 0.84 cm. In dry basis, the pulp represented 12.8 % of the fruit while the seed was preponderant representing 73.8 % of the fruit. Overall, the miracle fruits studied exhibited size and average mass 35 % lower than values reported in literature. Likewise, the pulp content is 33 % lower than those obtained in the literature. However, the miraculin concentration in the pulp was higher than those reported by other authors amounting to 4.8 g‧kg -1 DB. Heat treatments led to significant losses of miraculin. In the raw pulp (aw = 0.97), 70.5 % and 71.9 % of miraculin were lost after isothermal treatments for 5 min at 70 °C and 80 °C respectively. The intensity of degradation was slightly lower when the pulp was lyophilized up to a 0.31 aw with 66.8 % lost recorded at 70 °C (5 min). The findings highlight the potential of Beninese Sisrè as a natural sweetener, while also providing valuable insights for developing stabilization processes to obtain high-quality functional products
Enhancing Rockfall Detection Using Permanent LiDAR Scanner (PLS) Data and Automated Workflows at St. Eynard Cliff (Grenoble, France)
No full textInternational audienceThe ANR C2R-IA (anrc2ria.fr) project aims to develop reliable decision-making tools for dynamic rockfall risk management, such as restricting access to hazardous zones during critical periods. To achieve this, we aim to develop a predictive model for observed rockfall events that relates them to weather conditions history using Artificial Intelligence tools. Training an artificial neural network requires a comprehensively labelled dataset of rockfall events. To build this dataset, we deployed various instruments, including a Permanent LiDAR Scanner (PLS), whose data is processed by an automated workflow to handle the large volume of hourly-acquired point clouds.The workflow started with a pre-processing step that includes point cloud alignment (registration), quality control, cropping the area studied, and vegetation removal. During the processing phase, changes are identified using a multi-step approach:First, pairs of point clouds are aligned either globally or by spatial strips (Chanut et al. EGU 2025, poster session). Then, M3C2 distances (Lague et al, 2013) are calculated. For a pair of point clouds (N1, N2), the distance computation is made twice from N1 to N2 and from N2 to N1 to identify significant changes. Dense clusters of significant changes are extracted using DBSCAN clustering, and a spatial association between clusters from the two clouds is performed to track corresponding zones and ensure accurate changes in output. To refine block characterization, a local registration and comparison is further performed, followed by alphashape surface reconstruction for volume estimation. The workflow was developed in Python, primarily using the CloudComPy library, and requires minimal operator intervention thanks to integrated quality metrics at each processing step.This optimized workflow combined with a fixed point of acquisition (a reinforced concrete pillar) has significantly improved the detection threshold at the St. Eynard site (Grenoble, France), allowing for identifying rockfalls as shallow as 10 cm in depth and 0.01 m³ volume — an improvement from the previous 40 cm and 0.1 m³ (Verdier-Legoupil, 2023; Le Roy, 2020). Catalog completeness has also been improved, with the number of detected events increased thresholds from less than 50 events/month/km² to about 150 events/month/km². However, numerous false positives are generated, primarily due to persistent vegetation artifacts despite the vegetation removal step. To address this issue, future work will focus on integrating an automatic change validation method using criteria such as morphology, scalar field information, and additional point cloud comparisons to check the temporal persistence of changes.Chanut, M.-A., Manceau, L., Levy, C., Dewez, T., Amitrano, D., 2025. Rockfall detection using lidar point clouds: identification of geometric distortions during acquisition and proposed processing to enable a low detection threshold. EGU 2025, Poster session.Lague, D., Brodu, N., Leroux, J., 2013. Accurate 3D comparison of complex topography with terrestrial laser scanner: Application to the Rangitikei canyon (N-Z). ISPRS Journal of Photogrammetry and Remote Sensing 82, 10–26. URL https://doi.org/10.1016/j.isprsjprs.2013.04.009Le Roy, G., 2020. Rockfalls multi-methods detection and characterization. Université Grenoble Alpes.Verdier-Legoupil, M., 2023. Etude des chutes de blocs par la photogrammétrie, cas du St Eynard. Université Grenoble Alpes
Changement climatique en Outre-mer : Connaissances et Solutions d’adaptation
No full textNational audienceThe Earth and Space Research Observatory (Observatoire des Sciences de l'Univers, OSU) of Reunion Island (CNRS, IRD, Météo-France and University of Reunion Island), on behalf of the French Directorate General for Oversea Territories (Direction Générale des Outre-Mer, DGOM), is leading a literature review of knowledge and gaps on global climate change, its impacts and adaptation solution in French oversea territoires. Initiated in September 2023, this pluridisciplinary and collaborative project has the ambition to define a framework on climate change adaptation for national and local decision-makers, researchers and local communities. Through a knowledge mapping exercise, this project aims to review the scientific and institutional literature, as exhaustively as possible, and to present the observed and projected climate change for each oversea territory, accompanied by sectorial analyses including risks, impacts and adaptation options, and a synthesis of adaptation solutions in French oversea territories. In a changing world, developing the knowledge and awareness of institutions and their agents on the topic of global climate change, its impacts and potential adaptation solutions is key to anticipate and implement risk reduction strategies in the future. In this context, several presentations were realized in order to introduce (1) definitions and elements of context on global climate change (e.g., difference between mitigation and adaptation) and the necessity to adapt for the future, (2) the literature review lead by the OSU-Réunion, the results reflecting current progress at the time of the presentation, and adaptation initiatives adapted to each audience with the hope to inspire actions, and (3) foster discussion around the subject of adaptation. These presentations reflect the importance of training of public institutions' agents, as stated in the National Plan for Climate Change Adaptation (Plan National d'Adaptation au Changement Climatique, PNACC, published in 2024), while tailoring the message to the various local realities of French oversea territories and disseminating it beyond public institutions. This work was presented in person as part of the seminar InterSciences Vata of the Institut de Recherche et Développement (IRD) in New Caledonia, as well as at the Université de Nouvelle-Calédonie (UNC), in order to showcase the project and gather information from local researchers.L’Observatoire des Sciences de l’Univers (OSU) de La Réunion (CNRS, IRD, Météo-France et Université de La Réunion), pour le compte de la Direction Générale des Outre-Mer (DGOM), mène un projet de synthèse des connaissances et des lacunes sur les impacts du changement climatique et solutions d’adaptation dans les territoires d’outre-mer français. Initié en septembre 2023, ce projet pluridisciplinaire et collaboratif ambitionne de mettre en place un cadre de référence sur la thématique de l’adaptation au changement climatique pour les décideurs politiques, la communauté scientifique et les communautés locales. A travers un exercice de cartographie des connaissances, ce projet a pour objectif de réaliser une revue de la littérature scientifique et grise la plus exhaustive possible et de présenter le changement climatique observé et attendu pour chaque territoire ultramarin, des analyses sectorielles incluant les risques, les impacts et les possibilités d’adaptation, et une synthèse des solutions d’adaptation au changement climatique dans les outre-mer français. Face à un climat qui se dérègle, développer les connaissances des organisations et de leurs agents sur le changement climatique, ses impacts et les solutions d'adaptation possibles est primordial afin d'anticiper et de mettre en œuvre des stratégies de réduction des risques climatiques dans le futur. Dans ce contexte, plusieurs interventions lors de séminaires sont réalisées afin (1) d'apporter des éléments de définitions et de contexte autour du changement climatique (ex. différence entre atténuation et adaptation) et de la nécessité de s'adapter pour le futur, (2) de présenter le projet de synthèse de connaissances mené par l'OSU-Réunion, les résultats reflétant l'état d'avancement à la date de l'intervention, et des initiatives d'adaptation au changement climatique inspirantes et adaptées à chaque public et (3) de créer de la discussion autour de l'adaptation au changement climatique. Cette présentation a été réalisée dans le cadre du séminaire InterSciences Vata de l'Institut de Recherche et Développement (IRD) de Nouvelle-Calédonie, ainsi qu'à l'Université de Nouvelle-Calédonie (UNC) afin de présenter le projet aux chercheurs des ces deux institutions et de recueillir leurs opinions d'expert
„Und fröhlich sieht er das Insekt / Am Boden leblos ausgestreckt“: Mikroskopie der Unverhältnissmässigkeit Oder: Fliegenjagden in Kunst und Literatur
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Spatio-temporal distribution and environmental determinants of dengue vectors in Phnom Penh, Cambodia
No full textInternational audienceDengue fever, one of the most widespread vector-borne diseases globally, is mainly transmitted by Aedes aegypti and Ae. albopictus mosquitoes. In Cambodia, dengue has been a recurrent public health challenge, with major outbreaks occurring in 1995, 2007, 2012, and 2019. The latter epidemic severely impacted the capital, Phnom Penh, yet the spatial and temporal dynamics of the two key vector species had not been studied in this urban context. This study aimed to investigate how the distribution of Ae. aegypti and Ae. albopictus is organized in the urban and peri-urban landscapes of Phnom Penh. Ovitraps were deployed every two months over a year in 40 pagodas randomly selected across Phnom Penh, chosen to ensure future replicability of the study. The larvae collected were reared to adulthood for accurate species identification. High-resolution satellite imagery (SPOT7) and daily rainfall data were used to analyze the surrounding environments through remote sensing techniques. The results revealed distinct spatio-temporal patterns for each species: Ae. albopictus was associated with peri-urban areas rich in vegetation and water, while Ae. aegypti predominated in highly urbanized and construction-dense environments. Spatial analysis using buffer zones (250 m, 500 m, 1000 m) around trapping sites confirmed that the use of pagodas as proxies for urban sampling is effective. These findings highlight the importance of monitoring these vector species, particularly as Phnom Penh continues to undergo rapid environmental transformation. The identification of simple, remotely sensed environmental indicators offer a valuable tool for predicting future outbreaks and guiding targeted vector control strategies. This study also provides a replicable methodological framework to assess the impact of urbanization and climate change on dengue vector distribution in Phnom Penh and similar urban settings
Revisiting the Youngest Toba Tuff Super-Eruption: A high-resolution cryptotephra perspective from the Andaman Sea
No full textInternational audienceAround 74,000 years ago, the largest known volcanic eruption of the Quaternary occurred at Toba volcano, in Sumatra, Indonesia: the Youngest Toba Tuff super-eruption (YTT). Its widespread ash deposits have long been used as chronostratigraphic markers in paleoenvironmental and archaeological studies. However, new evidence challenges the conventional view of the YTT as a single, short-lived cataclysmic event. Analysis of volcanic deposits from marine core BAR94–25, drilled off the northern coast of Sumatra, reveals that volcanic activity at Toba continued for a long period of at least ∼50 kyr (∼101 to ∼49 ka). Using high-resolution cryptotephra stratigraphy, textural observations, and in-situ geochemical analyses (EPMA, LA-ICP-MS), three distinct Volcanic Activity Phases (VAP1–VAP3) were identified: (i) VAP1 (∼101 to ∼79 ka) representing pre-YTT activity, (ii) VAP2 (∼75 to ∼65 ka) corresponding to the YTT phase, including multiple eruptions over ∼10 kyr (YTTs), and (iii) VAP3 (64 to ∼49 ka) marking post-YTT explosive activity associated with caldera resurgence. Each phase produced highly evolved rhyolitic magmas characteristic of Toba, with distinct geochemical signatures (e.g. U/Th, Hf/Ta, Zr/Nb) indicating slight variations in late-stage differentiation from a common magmatic source. The YTT eruptions were fed by at least four compositionally distinct magma reservoirs, identified through Ba/Y and Sr/Y ratios of glass compositions, which were erupted simultaneously but in varying proportions throughout VAP2, rather than during a single event. This study highlights the need to reassess tephrostratigraphic correlations and the dating of sedimentary archives that rely on the traditional ∼74 ka YTT isochron
The INTERMAGNET framework for peer-review and activities for improvement of 1 min Definitive Data quality and availability
No full textInternational audienceAbstract. The global INTERMAGNET network provides the scientific community with geomagnetic time series data from its more than 100 member observatories. These time series include near real-time data (Reported), as well as post-processed data products such as Quasi-Definitive and Definitive Data (hereafter referred to as QD and DD, respectively). QD data is published online with a delay of up to 3 months, while DD data becomes available on the INTERMAGNET website after the end of each calendar year. Additionally, the DD data and metadata are published with a unique identifier (DOI). DD data publications cover the records since 1991, and occasionally include updates of previously published DD datasets. All datasets are publicly accessible online. DD and QD data allow the analysis of both short-term magnetic field variations and long-term secular variation. Monitoring these long-term changes distinguishes INTERMAGNET from other networks that focus primarily on short-term geomagnetic variations. INTERMAGNET ensures high-quality DD geomagnetic data through a rigorous two-stage, peer-reviewed quality control process. Although this process delays publication, it guarantees the final DD datasets' highest possible accuracy and reliability. This article discusses key aspects of the collection, processing, and publication of DD data within the INTERMAGNET network
Sensitivity of neutrino oscillations to the Earth's interior properties
No full textInternational audienceUnderstanding the Earth s internal structure remains a major challenge, as traditional geophysical methods face ambiguities in linking seismic observations to temperature, composition, or mass density variations. Atmospheric neutrinos offer a complementary probe: while traversing the Earth, they undergo flavor oscillations that depend on the local electron density, which reflects both mass density and composition
Multidecadal changes in hydrological droughts across Sub-Saharan Africa
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