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Uncertainty sources in a large ensemble of hydrological projections: Regional Climate Models and Internal Variability matter
No full textInternational audienceMulti-scenario, multi-model ensembles of hydrological projections are widely used to describe possible futures of regional hydrology and inform adaptation strategies. The Explore2 dataset is such an ensemble of river flow projections in Metropolitan France. It provides future simulations for 1735 catchments with modeling chains composed of different hydrological models forced by 36 regional climate projections based on bias-adjusted EUROCORDEX simulations. This study assesses the uncertainties of this ensemble with QUALYPSO, a method specifically designed to deal with incomplete ensembles and to disentangle and quantify all uncertainty sources, including that due to internal variability. Focusing on results obtained at the end of the century, this study shows a strong agreement between modeling chains towards decreases in low flows in a large southern part of France for a high-emission scenario, and very uncertain changes for the annual mean and high flows. Emission scenario uncertainty is the dominant source of uncertainty for low flows over the whole of France, and for mean annual flows in southeastern France. The contribution of the global and regional climate models is important for mean and high flows, especially in rainfall-dominated areas. Regional climate models contribute considerable uncertainty to low flows, much more than global models. The contribution of hydrological model uncertainty is large for low flows, moderate for mean annual flows, and small for high flows. For all climate and hydrological indicators, internal variability is often large and cannot be overlooked. It is often of the same order and sometimes larger than the uncertainty on the climate change response
While the wolf is away: Modelling the dynamics of a moose population in a protected area
No full textInternational audienceHigh-density populations can threaten the ecological integrity of ecosystems through cascading effects. In such cases, management practices must be guided by sufficient knowledge of the biological mechanisms at play. Simulation models are powerful tools for acquiring such knowledge. The moose (Alces alces americana) is a species that recently became overabundant in some areas of eastern North America, sometimes requiring specific management measures. While numerous models exist for moose population dynamics, few are adapted to high density populations like the one in Forillon National Park (Quebec, Canada), a protected area in which the moose's apical predator (grey wolf Canis lupus) is absent. We developed a sex-and age-structured population model respecting these conditions that we parameterized using pattern-oriented modelling to help explain the changes in moose density observed over nearly 4 decades. The most plausible sequence of vital rates identified exhibited negative density dependence in survival, reproduction and dispersal. Predation by alternative predators, black bears (Ursus americanus) and coyotes (Canis latrans), caused substantial mortality of calves each year. Unlike elsewhere in northeastern North America, winter tick only had a slight effect on calf survival. Variations in the population's sex ratio were mainly explained by sex-biased dispersal. Our study provides new insights concerning the dynamics of high-density ungulate populations in the absence of their apical predator, and our modelling approach helped reveal new methodological challenges and opportunities. We also present a comprehensive process to build and parameterize a complex population model using scarce data.</div
Participatory modelling for agroecological transitions: engaging stakeholders in transformative pathways
No full textInternational audienceCONTEXT. The worldwide use of synthetic pesticides has been rising for decades. Agroecology offers a promising alternative, but its adoption requires support from public policy and multi-scale institutional and social levers. Recent policy approaches integrate levers promoting collective and territorial collaboration, recognizing the local scale as crucial for agroecological transitions. These levers involve mobilizing territorial stakeholders and implementing context-specific levers.OBJECTIVE. Our objective is to better understand territorial levers that support agroecological transformation and associated practice change dynamics. We engaged with stakeholders using a generic territorial socio-ecological model to identify local levers and potential agroecological transition pathways.METHODS. In the Barrois region (Eastern France), a participatory modelling initiative involved stakeholders from a farming territory aiming to reduce pesticide use. Three participatory workshops were organized to: (1) identify context-relevant levers; (2) calibrate the model based on the territory's current state; and (3) explore agricultural trajectories and supporting levers.RESULTS AND CONCLUSIONS. The use of the model highlights the dynamic and multi-factor nature of transitions. The workshops fostered rich dialogue and proposals, playing a central role in co-construction. Participants collectively identified levers such as awareness-raising, training initiatives, new stakeholder networks, and evolving advisory services. However, these levers vary depending on farmers' sensitivities and production types. Discussions emphasized the importance of involving not only farmers but also consumers and supply chains to drive change.SIGNIFICANCE. This participatory approach produced a more realistic model and created learning opportunities for all participants (researchers and agricultural stakeholders), despite challenges like communicating complex theoretical concepts and vocabulary
Federate cross-disciplinary work on the effects of pesticides on all aspects of health (human, animal, environmental)
No full textPlant protection products used in agriculture contain molecules specifically designed to be toxic to target organisms. However, their use can also have unintended effects, posing potential risks to ecosystems and non-target organisms, including humans. Research has deepened our understanding of the links between exposure to these substances and the effects observed in the environment. In particular, studies have highlighted how even low levels of exposure can cause chronic effects on non-target organisms and disrupt ecosystems. These findings underscore the importance of quantifying and characterising these exposures in order to better assess their potential impacts on human health and the environment.International audienceAs part of the Ecophyto II+ plan, now known as the Ecophyto 2030 strategy, research projects have been funded to increase knowledge about exposure to plant protection products (PPPs) and their impacts on health and the environment. These studies have led to the development of methodologies for pesticide monitoring and improved risk assessment. We provide a synthesis of the results of these projects and a discussion of key issues-risk assessment, regulation, and collective responsibility-to inform public policy and promote sustainable agricultural practices. Future perspectives include the assessment of chemical interactions in the context of climate change. An interdisciplinary approach and collaboration between researchers, health professionals, farmers, the agro-industry, and public authorities are essential to reduce the risks associated with pesticide use
Solutions et outils pour faire face à l’Herbe de la pampa – Un webinaire du centre de ressources EEE
No full texthttps://especes-exotiques-envahissantes.fr/solutions-et-outils-herbe-de-la-pampa/Le Centre national de ressources sur les espèces exotiques envahissantes a organisé le mardi 20 janvier 2026, avec l’Office français de la biodiversité (OFB), le Conservatoire d’espaces naturels de Nouvelle-Aquitaine (CEN-NA) et le Conservatoire botanique national Sud-Atlantique (CBN-SA), un webinaire de 2 heures qui portait sur les solutions et les outils pour faire face à l’Herbe de la pampa (Cortaderia selloana)
An angiosperm‐wide perspective on reproductive strategies and floral traits
No full textInternational audienceFlowering plants have many modes of sexual reproduction, notably varying from selfing to outcrossing, and from bisexual flowers to individuals with separate sexes (dioecy). These reproductive modes are associated with floral and life‐history traits that have evolved together, making it difficult to interpret correlations between traits. We analysed variation in 21 traits related to flowers, pollination, mating, sexual systems and life history from 361 species representative of flowering plant diversity. Outcrossing was mainly found among long‐lived, large‐stature plants, but hermaphroditic outcrossers and dioecious species appeared as largely nonoverlapping strategies in the trait space. Level of floral investment was the main difference between these strategies, with dioecious species having generally smaller, less rewarding flowers, a pattern that also occurred in biotically pollinated species. This multi‐trait study shows that pollination can be achieved in many, often contrasting, ways. Despite extensive variation in reproductive traits, dioecy stands out as being linked to floral traits primarily, while correlations with lifespan and dispersal traits appear spurious. We provide a conceptual framework based on lifespan, floral investment and sexual separation that can be used to integrate pollination, reproduction and plant growth in future research on plant evolution and ecology
Systèmes de culture agroécologiques légumiers incluant la carotte, économiquement viables et économes en produits phytosanitaires
No full textCe numéro fait suite au carrefour de l'innovation agronomique dédié au résultats des projets DEPHY EXPE 2 - Des systèmes utilisant les pesticides en ultime recours : résultats et enseignements de 6 ans d’expérimentations le 13 mars 2025 co-organisé par Inrae, Agreenium, la cellule d'Animation Nationale du réseau DEPHY Ecophyto et le lycée agricole du Valentin. Sont présenté les résultats des projets DEPHY EXPE 2 arrivant à leur terme en décembre 2024 pour diffuser les connaissances des principaux enseignements de ces essais « systèmes » qui ont éprouvé pendant 6 ans des combinaisons de leviers alternatifs à la lutte chimique pour maîtriser les bioagresseurs des cultures : diversification de l’agroécosystème, méthodes de contrôle biologique, choix de matériel végétal, stratégie d’évitement, prophylaxie… Les modalités de mises en œuvre des alternatives testées, leurs conditions de réussite et de diffusion et leurs impacts sur les performances techniques, économiques et environnementales de systèmes ont été discutées.National audienceThe AlterCarot project aimed to design, test, and evaluate economically viable vegetable cropping systems—including carrot cultivation—with the use of plant protection products only as a last resort. The objectives were: (1) to reduce the Treatment Frequency Index (TFI) by at least 60 % across all tested cropping systems, particularly for carrot and green bean; and (2) to anticipate the short- and medium-term withdrawal of active substances. From 2019 to 2024, five innovative cropping systems were tested in thetwo main carrot-producing regions in France, applying 88 decision rules combining various agronomic levers. Two systems achieved or even exceeded the TFI reduction targets (up to 71 %). However, the lack of sufficiently effective alternatives for certain pests led to increased risk-taking, significantly impacting agronomic and economic outcomes. The project highlights the progress still needed—especially in research and experimentation—and emphasizes the importance of building on achievementsand facilitating the transfer of decision rules.Le projet AlterCarot visait à concevoir, tester et évaluer des systèmes de culture légumiers (nommés par la suite « systèmes ») incluant la carotte, économiquement viables et n'utilisant les produits phytosanitaires qu'en ultime recours. Les objectifs étaient (1) de réduire l'indice de traitement phytosanitaire (IFT) d'a minima 60 % sur l'ensemble des systèmes testés, et sur la carotte et le haricot vert en particulier ; (2) d'anticiper les retraits de substances actives à court et moyen termes. De 2019 à 2024, cinq systèmes innovants ont été expérimentés dans les deux principaux bassins de production français de carotte, mobilisant 88 règles de décision (RdD) combinant divers leviers agronomiques. Deux systèmes ont atteint, voire dépassé les objectifs de baisse d'IFT (jusqu'à 71 %). Néanmoins, l'absence de leviers suffisamment efficaces contre certains bioagresseurs s'est accompagnée d'une forte prise de risque, impactant significativement les résultats agronomiques et économiques des systèmes. Le projet souligne les progrès encore nécessaires, en particulier en matière de recherche et d'expérimentation, et met en avant l'importance de capitaliser les acquis et de faciliter le transfert des RdD pour atteindre des systèmes économiquement viables
Intensive management negatively impacts field margin ecosystem service indicators at both field and landscape levels
No full textInternational audienceVegetated field margins generally increase plant biodiversity and connectivity in agricultural landscapes. They can deliver ecosystem services, such as providing food and shelter for insects, or maintaining biotic regulation. But they can also represent a risk, for example by hosting competitor plants or cultivated crop pests. In this work, we evaluated the effects of agricultural practices on indicators of three ecosystem services (providing floral resources for pollinators, reducing soil erosion and conserving plant biodiversity), and one ecosystem disservice (competing with the crop by hosting problematic weeds). We used a French nationwide‐scale monitoring network, composed of more than 450 fields of cereals, vineyards, and market gardening. Plant sampling and agricultural practices surveys were conducted from 2013 to 2018. We unambiguously found that pesticide use, at either field or municipality levels, or both, had detrimental effects on ecosystem service indicators. Herbicide use and fertilization quantity decreased floral resources, affecting both their quantity and diversity. Pesticide use was also associated with fewer nature‐value species and more problematic weeds. Margin management could also sometimes affect the service and disservice indicators. This work not only increases the knowledge on the unintentional negative impacts of agricultural practices on ecosystem service indicators, and then probably on their delivery, but also demonstrates that pesticide reduction is positively associated with proxies for ecosystem services. It also stresses the fact that these practices have to be implemented at both field and municipality levels
Assessing the non-target effects of herbicides on field margin plant communities after controlling for soil, climate, local context and landscape metrics
No full textInternational audienceHighlights: • We used a national dataset of 500 sites monitored yearly from 2013 to 2018. • We analysed the effects of herbicides on plant margin communities. • Herbicides had a negative effect on richness and nature-value species. • Situations of risk for pesticides drift had a negative effect on margin flora.Abstract: Pesticides are often identified as one of the major causes of biodiversity decline in farmlands. However, our knowledge about this relationship has mostly being inferred from small to landscape-scale studies, or from indirect indicators of agricultural practices at large scales. Here, we used a national network of more than 500 sites monitored yearly from 2013 to 2018 in France to assess the non-target effects of herbicides on field margin plant communities. We used hierarchical generalized linear models to investigate the effects of practices on plant species richness, plant species evenness, proportion of nature-value plants, and proportion of grasses in field margins, while controlling for a large number of possible confounding effects. The intensity of herbicide use had a negative effect on plant species richness, and on the proportion of nature-value plants. In the margin of cereal fields, there was a negative effect of dicotyledon herbicides on richness and a negative effect of grass herbicides on species evenness. We also identified, in some specific crops, a negative effect of non-herbicide treatments on margin flora richness and on the proportion of nature-value plants. The presence of surrounding grasslands had a consistent favourable effect on richness and on the proportion of nature-value plants in field margins. Finally, situations of risk for pesticides drift had a negative effect on margin flora. This study confirms that reducing herbicide use represents a robust lever to maintain the floristic diversity of field margins, which could be combined with strategies reducing the risk of pesticide drift
Trap-dependence in capture–recapture studies: empirical evidence in vertebrates and biological meaning
No full textInternational audienceCapture-recapture (CR) models have been used for decades to estimate population size and demographic rates in natural populations from the monitoring of individuals. One of the most frequent deviations from assumptions required in CR studies is the immediate trap-dependence that corresponds to the correlation between capture events. We review empirical evidence of immediate trap-dependence across vertebrate populations where several capture types exist, record possible variation in the occurrence and the sign of trap-dependence and discuss its biological meaning. We highlight that when trap-dependence occurs, trap-happiness, the higher probability for an individual to be captured again at i + 1 if captured at i, is the rule rather than the exception, whatever the type of capture. However, the occurrence of trap-dependence varies among populations of a given species and only displays a moderate repeatability in a given species. It also varies within a population depending on sex, age, or type of mark, and reflects among-individual variation in personality (bold versus shy), social status, or ecological context. We argue that immediate trap-dependence can be seen as a form of dynamic heterogeneity, reflecting clear among-individual differences. Although trap-dependence is generally considered simply as a noise to account for, it has a clear biological meaning in terms of among-individual differences