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The carbon footprint of diatom molecular research
No full textInternational audienceCarbon footprints (CF) are usually drawn up on the scale of states, sectoral activities (e.g. agriculture) or institutions. However, in order to reduce greenhouse gas (GHG) emissions, it is interesting to investigate finer scales. And to fully understand all the issues related to the adoption of new technologies, their environmental impact is an element that needs to be considered. In this exploratory study, we are looking at the CF of diatom metabarcoding, on the one hand at the scale of research projects that have used this technology, and on the other hand at the scale of the data acquisition process leading to taxonomic inventories. However, there are no freely available tools for carrying out CF at these scales. We therefore adapted the tools provided by ADEME (The French Agency for Ecological Transition) and the French research initiative Labo1point5. On the one hand, the CFs of a panel of 29 research projects focusing mainly on tropical aquatic ecosystems, some of which using molecular methods, were produced. These CFs were used to establish a typology of projects, based on the contribution of different GHG emission items. In addition, the CFs associated to the diatom metabarcoding process were produced for 3 structures. They were compared to the CFs from the conventional method of acquiring diatom taxonomic data, using microscopy. Compared to microscopy, metabarcoding involves a large number of stages and a wide variety of operating procedures. Possible solutions to limit GHG emissions are suggested, and the main aim of this presentation is to open up a discussion on the subject, with a view to developing practices that are as carbon-free as possible, in anticipation to the routine and large-scale deployment of molecular methods. The presentation is accompanied by a poster giving the tools needed for each participant in the AquaEcOmics meeting to carry out the CF of their own research projects and metabarcoding processes
Towards sustainable nutrient management along the Land-Sea continuum, an integrated modeling perspective
No full textInternational audienceThe Land-Ocean Aquatic Continuum (LOAC) plays a pivotal role in the transfer and transformation of carbon and nutrients from terrestrial systems to coastal waters, critically influencing coastal eutrophication resulting from excessive nitrogen (N) and phosphorus (P) loads from rivers compared to Silica (Si). Indeed, both agricultural practices on land and biogeochemical processes in and near streams as well as within estuaries control the eventual export of carbon and nutrients into the coastal sea. To address the complex interplay of biogeochemical processes that govern these transfers, an integrated modeling approach combining agricultural practices (GRAFS, an agri-food system model), river network and wetland processes (pyNuts-Riverstrahler modelling framework), and estuarine dynamics (C-GEM model) was applied across metropolitan France over the 2014–2019 period. The estuarine dynamics were modelled only where relevant, on 40 macro-tidal estuaries along the French Atlantic coast. This comprehensive framework explicitly quantifies the cascading fluxes of Dissolved Organic Carbon (DOC), and different forms of N, P and Si from headwaters to estuarine outlets. In addition, three different scenarios of agricultural practices modulating N diffuse inputs were designed and applied ranging from ‘business as usual’ to a switch towards ‘agroecology’. The modeling chain described above was applied to all watersheds larger than 300 km2 (n = 80) using reference conditions representative of the 2014-2019 period and validated by an extensive riverine database of 392,870 measurements from 929 stations. This integrated approach allows quantifying potential excess in nutrient export into the coastal seas compared to Redfield ratios between N, P and Si. Our simulations reveal that even under the most optimistic trajectories of nutrient reduction from agricultural practices, some coastal regions such as those flowing into the Celtic Sea will still experience nutrients exports above admissible values, despite in and near streams processes in rivers and estuaries typically removing 20-60% of the nutrient inputs from the land. Our results thus highlight the need for an integrated approach of nutrient management strategies encompassing terrestrial ecosystems, inland and coastal waters. Such an approach is needed to evaluate how these management strategies can help achieve sustainable water quality thresholds across the interconnected aquatic ecosystems of the LOAC
Juveniles at risk: behaviour and colour changes in sole juveniles (Solea solea) after exposure to estuarine ragworms (Hediste diversicolor) contaminated with microplastics
No full textInternational audienceDue to strong anthropogenic pressures and their location at the interface between continental and oceanic environments, estuarine areas are affected by significant diverse pollution and species that live in these areas are particularly exposed. Microplastic (MPs) pollution is a worldwide issue and causes substantiated trouble in estuaries where sometimes the number of MPs equal or exceed the number of fish larvae which suggest a high risk of contamination of biota especially in benthic organisms and demersal fish. There are growing evidence that, beyond intrinsic toxicity, MPs can transfer chemicals (additives or pollutants). In order to get closer to environmental situations, in this study we tackled an issue that is rarely dealt with, namely the trophic transfer of MPs and chemicals through the food chain between a sediment- and a benthic-feeder. To take into account these specificities, we used an emblematic and common species of the European coastlines, the common sole (Solea solea) and its annelid prey.Sole juveniles were fed with estuarine ragworms (Hediste diversicolor) previously exposed to MPs via enriched MPs sediment. The MPs used were either a mixture of micronized plastics collected from the Seine Estuary (eMPs, two environmental concentrations at 1 or 100 mg/kg of sediment, median size range 52-77 μm) or model MPs of PVC particles (at 1 g/kg of sediment, size range 125-250 μm), either uncontaminated or contaminated with Benzo(a)Pyrene (BaP, 11.5 μg/g MPs) or benzophenone-3 (BP3, 66 ng/g MPs). Several indicators of health status such as survival, growth, behaviour, energy metabolism, and histopathology were studied. Sole individuals fed ragworms exposed to eMPs or PVC MPs displayed a change in behaviour (place preference between black/white background). Seine Estuary eMPs lead to an increase in body colour chroma for the highest concentration and behaviour was modified with an increase in time spent on white bottom and transition number for the highest concentration when distance moved increased only at the lowest concentration. Sole exposed to BaP-PVC-MPs displayed the lowest time spent on white background compared to control and BP3-PVC-MPs group. Soles exposed to BP3-PVC MPs displayed a significant skin colour increase in chroma and a wider combination of value/chroma reflecting more diverse skin colours. Finally, lipid content in muscle and DNA damage were significantly higher in BP3-MPs. Although the exact mechanisms underpinning such changes are largely unknown, these observations are indicative of physiological stress which may have a significant impact on survival by increasing predation risks for fish juveniles, hence the ecosystem health and calls for further trophic transfer experimental research
The effect of seismic air gun shots on physiology and behaviour of fish lake communities
No full textInternational audienceAlterations in the acoustic environment owing to anthropogenic sound are recognised as global pollution and strengthening studies in freshwater. This study focuses on the impact of lake seismic surveys on fish. First, we measured individual stress responses, i.e. cortisol levels and oxidative stress, morphological parameters, and stomach contents of juvenile roaches (Rutilus rutilus) captured by trawling prior to and during the seismic survey. Second, using hydroacoustics, we analysed individual fish and school behaviour before, during, and after the shots. We collected environmental DNA (eDNA) and analysed the concentrations of three species to assess their littoral refuge. Finally, using hydroacoustics, we assessed pelagic fish density before, during, and after the shots. We demonstrated that the shots noticeably impacted juvenile roaches, from the molecular and cellular level to individual morphological characteristics. During the seismic shots, changes in school characteristics were observed. At the onset of the seismic survey, a sharp decrease (> 30%) in pelagic fish density was observed, and no increase in fish density in the littoral area was noted for the three species. These responses suggest that sound disturbances due to air gun shots affect fish in multiple ways (physiology, morphology, behaviour, and habitat use) and across multiple biological scales
Singing around the volcano: Detecting baleen whales in the Mozambique channel based on their song rhythms, from seismic and hydroacoustic data
No full textInternational audienceSince March 2019 and October 2020, two long-term submarine networks—comprising ocean bottom seismometers and water-column hydrophones—have been deployed in the northern Mozambique Channel (Western Indian Ocean) to monitor the seismo-volcanic crisis that began offshore Mayotte in 2018. These deployments provide a valuable multi-year dataset for environmental monitoring in this remote region, including seasonal variations in the presence of baleen whales. To analyze these patterns, we developed an automated detector for stereotyped and regular signals, focusing on the characteristic inter-call intervals of each whale species, independently of the song structure. The detector's simplicity makes it computationally efficient and easily adaptable to species vocalizing in the 15–100 Hz frequency range over extended periods. Analysis of nearly six years of continuous seismo-acoustic data highlights the seasonal presence of Antarctic blue whales (May–August), Southwest Indian Ocean pygmy blue whales (bi-modal pattern from April–August and October–January), minke whales (June–December), and fin whales (July–November), and highlights the potential variability over years. Our results enhance and refine our understanding of the seasonal migration patterns of whale populations in this specific area of the Western Indian Ocean
Comportement du méthane dans l’atmosphère et analyse des enjeux techniques du PRG100 et du PRG* - application au secteur des ruminants en France et en Europe. AScA, Oxford Martin School, Cranfield University, rapport pour l’OFB, 2025, 44p.: Note de synthèse dans le cadre de l’étude : Analyse des métriques climat et conséquences sur la compréhension de la contribution des ruminants au changement climatique et sur l’agenda de conservation de la biodiversité
No full textRuminants are often viewed negatively because of their emissions of methane, a powerful but short-lived greenhouse gas. Yet they play a key role in the conservation of grasslands and open landscapes, which are essential for biodiversity, particularly in Europe, where extensive livestock farming has shaped semi-natural habitats for centuries. A poor understanding of the real impact of methane can lead to political decisions that neglect both holistic climate and biodiversity issues. This report, commissioned by the French Office for Biodiversity (OFB), analyses the limitations of GWP100, the metric currently used to account for emissions, and contemplates GWP* as a relevant complement.Main findings:1. Methane: a short-lived greenhouse gaso Unlike CO₂, which persists for centuries, methane has a lifespan of about twelve years.o Its warming effect is very strong in the short term, but it does not accumulate in the atmosphere.o The key criterion for understanding the impact of a methane emissions regime on temperature change is therefore their variation over a few decades, which determines that of its atmospheric concentration and therefore the final impact on temperature.o Increasing methane emissions lead to warming; decreasing emissions (by more than 10% in 30 years) lead to a cooling effect.2. Shortcomings of GWP100o GWP100 is the most commonly used metric to approach climate change. It expresses methane emissions in ‘CO₂ equivalent’, without taking into account its short lifespan. It therefore assimilates methane to a long-lived greenhouse gas.o It overestimates the effect of stable or falling emissions and underestimates that of sharply rising emissions.o This can lead to poorly designed policies in terms of priorities, by gas and by sector.3. The contribution of GWP*o GWP* provides a better account of the physics of methane and incorporates the short lifespan of methane and the dynamics of emissions over 20 years to estimate an impact on temperature change.o It offers a better assessment of the real climate impact of a methane-emitting sector over time, including agriculture, on the climate.o It provides a better understanding of the priorities between the different greenhouse gases.o It is recognised as a valid metric in the work of the 6th IPCC report, which leaves the choice of metric open depending on the stated climate and sectoral objectives.4. A change of focus for European agriculture: the role of nitrous oxideo In Europe, methane emissions from the agricultural sector have decreased since the 1990s.o Due to the fall in methane emissions in the EU27, nitrous oxide (N₂O), mainly coming from agricultural fertilisers, is becoming the main warming factor in the European agricultural sector.o Better consideration of this gas is essential to define effective climate strategies, taking better account of the medium and long term climate impacts.5. Implications for agriculture and biodiversityo Extensive ruminant farming, particularly in Europe, helps to preserve biodiversity by maintaining permanent grasslands and natural habitats. It also contributes to the closing of biogeochemical cycles, particularly that of nitrogen.o A more precise approach to climate would make it possible to avoid policies that penalise sustainable livestock farming, to the detriment of the climate and other environmental issues.The choice of metrics used to measure greenhouse gas emissions has a profound influence on climate strategies. By better integrating methane dynamics, GWP* offers a science-based approach that is better suited to the challenges of the European agricultural sector. It would make it possible to prioritise climate issues more effectively by balancing the reduction of methane with that of nitrous oxide and CO₂, while preserving biodiversity and sustainable agriculture.Les ruminants sont souvent perçus négativement en raison de leurs émissions de méthane, un gaz à effet de serre puissant mais à courte durée de vie. Pourtant, ils jouent un rôle clé dans la conservation des prairies et des milieux ouverts, essentiels à la biodiversité, en particulier en Europe où l’élevage extensif a façonné les paysages depuis des siècles. Une mauvaise compréhension de l’impact réel du méthane peut conduire à des décisions politiques qui négligent les enjeux tant climatiques que biodiversité. Ce rapport, commandé par l’Office Français de la Biodiversité (OFB), analyse les limites du PRG100, la métrique actuellement utilisée pour comptabiliser les émissions, et propose le PRG* comme complément pertinent.Principaux constats :1. Le méthane : un gaz à effet de serre à courte durée de vieo Contrairement au CO₂, qui persiste pendant des siècles, la durée de vie du méthane est d’une douzaine d’années.o Son effet réchauffant est très fort à court terme, mais il ne s’accumule pas dans l’atmosphère.o Le critère clé pour comprendre l’impact d’un régime d’émissions de méthane sur le changement de température est donc leur variation sur quelques décennies, qui détermine celle de sa concentration atmosphérique et donc l’impact final sur la température.o Des émissions croissantes de méthane conduisent à un réchauffement ; des émissions décroissantes (de plus de 10% en 30 ans) conduisent à un effet refroidissant.2. Les limites du PRG100o Le PRG100 est la métrique la plus communément utilisée pour approcher le changement climatique. Il exprime les émissions de méthane en "équivalent CO₂", sans tenir compte de sa courte durée de vie. Il assimile donc le méthane à un gaz à effet de serre à longue durée de vie.o Il surestime l’effet des émissions stables ou en baisse et sous-estime celui des émissions en forte hausse.o Cela peut mener à des politiques mal calibrées en termes de priorités, par gaz et par secteurs.3. L’apport du PRG*o Le PRG* permet de mieux rendre compte de la physique du méthane et intègre la courte durée de vie du méthane et la dynamique des émissions sur 20 ans pour estimer un impact sur la température.o Il offre une meilleure évaluation de l’impact climatique réel d’un secteur émetteur de méthane, dont l’agriculture, sur le climat.o Il permet de mieux éclairer les priorités entre les différents gaz à effet de serre.o Il est reconnu comme une métrique valide dans les travaux du 6ème rapport du GIEC, qui laisse ouvert le choix de la métrique en fonction des objectifs climatiques et sectoriels affichés.4. Un changement de focus pour l’agriculture européenne : le rôle du protoxyde d’azoteo En Europe, les émissions de méthane du secteur agricole ont diminué depuis les années 1990.o En raison de la baisse des émissions de méthane en Europe, le protoxyde d’azote (N₂O), issu principalement des engrais agricoles, devient le principal facteur réchauffant du secteur agricole.o Une meilleure prise en compte de ce gaz est essentielle pour définir des stratégies climatiques efficaces, prenant mieux en compte les moyen et long termes.5. Implications pour l’agriculture et la biodiversitéo L’élevage de ruminants extensif, en particulier en Europe, contribue à préserver la biodiversité en maintenant des prairies permanentes et des habitats naturels. Il contribue également au bouclage des cycles biogéochimiques et celui de l’azote en particulier.o Une approche climatique plus précise permettrait d’éviter des politiques qui pénaliseraient l’élevage durable, au détriment du climat et d’autres enjeux environnementaux.Le choix des métriques utilisées pour mesurer les émissions de gaz à effet de serre influence profondément les stratégies climatiques. Le PRG*, en intégrant mieux la dynamique du méthane, offre une approche plus juste et adaptée aux réalités du secteur agricole européen. Il permettrait de mieux hiérarchiser les enjeux climatiques en équilibrant la réduction du méthane avec celle du protoxyde d’azote et du CO₂, tout en préservant la biodiversité et une agriculture durable
Climate Impacts on Lake Food‐Webs Are Mediated by Biological Invasions
No full textInternational audienceABSTRACT Climate change and biological invasions are among the most important drivers of biodiversity and ecosystem change. Despite major advances in understanding their ecological impacts, these drivers are often considered individually, overlooking their possible complex interrelationship. By applying structural equation modeling to an extensive nationwide dataset of 430 fish communities across 257 French lakes, we investigated how taxonomic, size, and trophic diversities are impacted by climate warming and exotic species occurrence. Our goal was to compare their relative signature or lasting impacts after these factors had taken effect and to determine whether climate warming and biological invasions mediate the current state of community diversities. Drawing on a set of interconnected hypotheses, we suggest that biological invasions could be an important indirect effect of climate warming. This aspect must be considered to fully grasp the overall effects of climate change, beyond just its direct thermal impacts. Our results support our hypothesis that climate warming negatively impacts size and trophic diversities. However, these effects are mostly mediated by the warming‐induced increase in exotic species richness, which, in turn, promotes total species richness. These results suggest that exotic species have a substantial role in determining the impact of climate change, obscuring the diversity patterns predicted by temperature alone. We conclude that the impacts of climate change cannot be understood without considering its mediated effects via biological invasions, underscoring the need to grasp their intertwined roles in predicting and managing ecological consequences
Rapport annuel du Réseau Ours Brun Ours 2024
No full textThe Pyrenean brown bear is annually monitored by cross-border wildlife services involving Andorran, Spanish andFrench teams. In France, the OFB, through the Brown Bear Network (ROB), is in charge of this task.In 2024, 3,593 indirect bear signs were collected as part of this cross-border monitoring programme, allowing theestimation of the brown bear distribution range over the entire Pyrenean massif at 7,200km², that is 100km² more than in2023 and 1,500km² more than in 2022. Despite numerous fluctuations since the first translocations in 1996, the general trend ofthe distribution area is still upwards.All these different signs of presence, combined with the genetic analysis of 881 of them (hair and scat samples), madeit possible to identify 96 different individuals in the Pyrenees and to detect a minimum of 13 litters totalling 22 cubs of the year.2024 is thus the year in which the highest number of females with cubs of the year has been observed since the firsttranslocations in 1996. At least 9 of the 16 cubs born and detected in 2023 were detected alive in 2024, giving a provisionalsurvival rate of 56.25%. 13 individuals detected in 2023 were not detected in 2024 but are not considered as disappeared fornow. In contrast, 5 bears are considered disappeared in 2024.The detection of 7 bears in 2024 (5 adult females and 2 sub-adult females), not detected in 2023, means that 7individuals can be added to the Minimum detected size of 2023, giving a Minimum retained size (MRS) for 2023 of 90 bearsacross the Pyrenees. Based on the MRS, the average annual growth rate between 2006 and 2023 is estimated at+11.12% for the whole Pyrenees range.In 2024, the CMR (Capture-marked-recapture) method estimates the population size at 104 individuals, with acredibility interval ranging from 97 to 123 individuals. Demographically, the population is continuing to increase steadily.However, a demo-genetic study is currently underway to quantify the effects of inbreeding on the demography of the Pyreneanbrown bear population.La población de oso pardo en los Pirineos es objeto de un seguimiento transfronterizo anual en el que participan lasadministraciones andorranas, españolas y francesas. En Francia, la OFB, a través de la Red Oso Pardo (ROB), se encarga de estatarea.En 2024, los 3.593 indicios indirectos de oso recogidos en el marco de este programa de seguimiento transfronterizopermiten estimar el área de distribución del oso en todo el macizo pirenaico en 7.200 km², lo que supone un aumento de 100km² con respecto a 2023 y de 1.500 km² con respecto a 2022. A pesar de las numerosas fluctuaciones desde las primerasreintroducciones en 1996, la tendencia general del área de distribución sigue siendo al alza.Todos estos diferentes indicios de presencia, combinados con el análisis genético de 881 de ellos (muestras de pelo yexcrementos) permiten identificar 96 individuos diferentes y detectar un mínimo de 13 camadas que totalizan 22 oseznos delaño. Esto convierte a 2024 en el año en que se ha observado el mayor número de hembras con crías del año desde lasprimeras reintroducciones en 1996. Al menos 9 de las 16 crías nacidas y detectadas en 2023 fueron detectadas vivas en 2024, loque arroja una tasa provisional de supervivencia del 56,25%. 13 individuos detectados en 2023 no fueron detectados en 2024,pero no se consideran desaparecidos por el momento. Sin embargo, 5 osos se consideran desaparecidos en 2024.La detección de 7 osos en 2024 (5 hembras adultas y 2 hembras subadultas), no detectados en 2023, significa quepueden añadirse 7 individuos al Efectivo mínimo detectado (EMD) en 2023, lo que da un Efectivo mínimo retenido (EMR) para2023 de 90 osos en todos los Pirineos. Sobre la base del EMR, la tasa media de crecimiento anual entre 2006 y 2023 se estimaen +11,12% para todos los Pirineos.En 2024, el método CMR (Captura-marcaje-recaptura) estima la población en 104 individuos, con un intervalo decredibilidad de entre 97 y 123 individuos. Demográficamente, la población sigue aumentando de forma constante. Sinembargo, actualmente se está realizando un estudio demogenético para cuantificar los efectos de la endogamia, observada enlos últimos años, sobre la demografía de los osos en los Pirineos.La population d’Ours brun présente dans les Pyrénées fait l’objet d’un suivi annuel transfrontalier impliquant les services andorrans, espagnols et français. En France, l’OFB, par le biais du réseau Ours Brun (ROB), est chargé de cette mission. En 2024, les 3 593 indices indirects d’ours collectés dans le cadre de ce suivi transfrontalier permettent d’estimer l’aire de répartition de l’ours sur l’ensemble du massif Pyrénéen à 7 200 km², soit une augmentation de 100 km² par rapport à 2023 et de 1 500km² par rapport à 2022. Malgré de nombreuses fluctuations depuis les premières réintroductions en 1996, la tendance générale de l’aire de répartition est toujours à l’augmentation. L’ensemble de ces différents indices de présence, associé à l’analyse génétique de 881 d’entre eux (échantillons de poils et de crottes) permet d’identifier 96 individus différents et de détecter un minimum de 13 portées totalisant 22 oursons de l’année. 2024 devient ainsi l’année où est observé le plus grand nombre de femelles suitées depuis les premières réintroductions de 1996. Au moins 9 individus sur 16, nés et détectés en 2023, ont été repérés vivants en 2024, soit un taux de survie provisoire de 56,25%. 13 individus détectés en 2023 n’ont pas été repérés en 2024 mais ne sont pour autant considérés disparus pour l’instant. En revanche, 5 ours sont considérés disparus en 2024. La détection de 7 ours en 2024 (5 femelles adultes et 2 femelles subadultes), non repérés en 2023, permet donc d’ajouter 7 individus à l’Effectif minimal détecté (EMD) de 2023 et d’obtenir ainsi un Effectif minimal retenu (EMR) pour 2023 de 90 ours sur l’ensemble de la chaîne des Pyrénées. Sur la base de l’EMR, le taux d’accroissement moyen annuel entre 2006 et 2023 est estimé à +11,12% pour l’ensemble des Pyrénées. En 2024, la méthode CMR (Capture-marquage-recapture) évalue la population à 104 individus, avec un intervalle de crédibilité compris entre 97 et 123 individus. Sur le plan démographique, la population continue ainsi d’augmenter progressivement. Une étude démo-génétique en cours permettra néanmoins de quantifier les effets de la consanguinité, constatée ces dernières années, sur la démographie des ours des Pyrénées
Mise à jour des estimations démographiques et des effectifs de la population de loups en France lors de l'hiver 2023/2024
No full textThe wolf population (Canis lupus) in France is monitored annually by the wolf-lynx network, led by the French Biodiversity Agency. This technical report presents an update on demographic parameters and population size following the 2023/24 winter field campaign. The genotyping of DNA from collected biological samples (feces, hair, urine, blood, and tissue from dead wolves) provides the genetic identity of individuals and forms the basis for estimating demographic parameters and population size. As in previous years, capture-recapture methods were used to account for the imperfect detection of individuals in the population.The 2023/24 winter field campaign was characterized by increased sampling effort, resulting in a larger volume of genetically analyzed biological samples. A new sampling protocol, that was based on a goal in terms of number of biological samples collected per grid cell, allowed the homogenization of the collection of samples across the population range, and increased the probability of detecting individuals compared to previous winters.As in previous years, there was a strong individual heterogeneity in detection probability. The annual survival probability decreased from 71% (95% confidence interval: 66-77%) during the 2014-18 period to 62% (95% CI: 56-69%) during the 2019-24 period. The last period corresponded to a change in derogatory culling regime, which increased from about 10% of the population during 2014-18 to 19% during 2019-24.The analysis indicated that wolf population size in France during the winter 2023/24 was likely between 920 and 1125 individuals. These two values correspond to the lower and upper bounds of the 95% confidence interval. There was a marked increase in the precision of the estimates compared to previous years, which was mostly caused by the larger field effort and by better accounting for various sources of heterogeneity in detection probability.Since the winter 2021/22, population estimates have remained within a similar range (825-1635 in 2021/22; 750-1344 in 2022/23; 920-1125 in 2023/24). Conclusions on the demographic trend of the population should be drawn from multi-year timeseries to identify demographic trajectories, particularly given the degree of uncertainty associated with these estimates. In this regard, understanding the underlying demographic parameters is crucial for interpreting these trends: the observed decrease in survival, which is at the threshold of maximum mortality tolerable to maintain stable growth, suggests a trend towards a stable population size.La population de loups (Canis lupus) en France fait l’objet d’un suivi annuel mené par le Réseau Loup Lynx piloté par l’Office Français de la Biodiversité. Ce rapport technique présente la mise à jour des paramètres démographiques et des effectifs à la suite de la campagne de terrain de l’hiver 2023/24. Le génotypage de l’ADN issu des indices biologiques collectés (fèces, poils, urines, sang et dépouilles des loups morts) permet d’obtenir l’identité génétique des individus et constitue les données de base pour l’estimation des paramètres démographiques et des effectifs. Comme les années précédentes, les méthodes de capture-recapture ont été utilisées pour prendre en compte la détection partielle des individus de la population. La campagne de terrain de l’hiver 2023/24 est caractérisée par une augmentation de l’effort d’échantillonnage sur le terrain, avec comme conséquence une augmentation du volume d'indices biologiques analysés génétiquement. Un plan d'échantillonnage, basé sur des objectifs de nombre d’indices biologiques récoltés par maille, a permis d’homogénéiser la collecte sur l’aire de distribution et d’augmenter la probabilité de détection des individus en comparaison des campagnes précédentes.Comme les années précédentes, une forte hétérogénéité dans la probabilité de détecter les individus est mise en évidence par les analyses. La survie annuelle des individus a diminué en passant de 71% (intervalle de confiance à 95%= 66-77%) pendant la période 2014-18 à 62% (95% CI= 56-69%) pendant la période 2019-24. Cette dernière période correspond au changement de régime de prélèvement dérogatoire qui est passé d’environ 10% de la population sur la période 2014-18 à 19% en 2019-24.Les estimations d’effectifs montrent que le nombre de loups en France lors de l’hiver 2023/24 se situe vraisemblablement entre 920 et 1125 individus. Ces deux valeurs correspondent aux bornes basse et haute de l’intervalle de confiance à 95%. On remarque une nette amélioration de la précision de l’estimation par rapport aux estimations des années précédentes qui s’explique principalement par une augmentation de l’effort de terrain et une meilleure prise en compte des différentes sources d'hétérogénéité associées à la détection des individus. Pour autant, depuis l’hiver 2021/22, l’estimation des effectifs se situe dans la même gamme de valeurs (825-1635 en 2021/22 ; 750-1344 en 2022/23 ; 920-1125 en 2023-24). Les conclusions sur la tendance démographique de la population doivent se faire sur des séries pluriannuelles pour identifier les trajectoires démographiques des populations, particulièrement au vu du degré d’incertitude associé à ces estimations. La connaissance des paramètres démographiques sous-jacents est une information importante pour permettre l'interprétation de ces tendances : la diminution du taux de survie ici mesurée, qui se situe au niveau des seuils maximum de mortalité supportable pour maintenir une croissance stable, suggère une tendance à la stabilisation des effectifs
An integrative framework to combine migratory connectivity and demographic data
No full textInternational audienceMigratory species experience various conditions and events throughout their annual cycle that influence their spatial and demographic dynamics. To understand these dynamics, it is essential to describe the origin and destination of individuals. Migratory connectivity, which is defined as the geographic linkage between populations across the annual cycle, is increasingly incorporated in population models to relate population trends to environmental variables at different stages of the cycle. However, such information on migratory movements is obtained independently from the study of population dynamics despite the interaction between both processes. Expanding on the growing use of integrated modelling approaches, we developed an integrated framework that allows the sharing of information between migratory connectivity and population data. We first assembled an integrated migratory connectivity model and an integrated population model to join the analysis of GPS, live‐reencounter, dead‐recovery, capture–mark–recapture, and population count data within a unified framework. Based on simulated data, we assessed the ability of the resulting integrated connectivity and population model to produce unbiased and precise connectivity and demographic estimates. We then applied the same assessment to real data using the Eurasian Curlew ( Numenius arquata ) as a case study. On simulated data, the integrated connectivity and population model estimated connectivity and survival parameters with no bias and similar precision to the connectivity model alone. However, it outperformed the population model in estimating fecundity in the absence of explicit productivity data. When applied to the Eurasian Curlew, the integrated connectivity and population model produced overall similar migratory connectivity and more accurate demographic estimates than the connectivity model alone, consistent with previous studies. Additionally, the model was able to estimate fecundity, whereas the data were too sparse for the population model alone to disentangle juvenile survival and fecundity. The sharing of information between migratory connectivity and population data improved the estimation of demographic parameters by the population model and improved connectivity parameter estimates when data were scarce. This flexible framework can be generalised to include diverse data on migration movements, population structure, individual heterogeneity or environmental variables, allowing further investigation of the interaction between migration patterns and population dynamics