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Evidence of Geological Control on the Hydrological Response of Tropical Volcanic Catchments
No full textInternational audienceThe aim of this study is to assess the key drivers of runoff generation in permeable volcanic catchments, and notably the role of geology. Therefore, the hydrological response of 28 catchments located on the tropical volcanic Island of la Réunion, characterised by strong climatic forcing and geological contrasts, was studied. High‐frequency measurements (15‐min time step) of radar rainfall and discharge records over the 2014–2022 period were analyzed to develop a hydroclimatic database including 4591 storm‐flood events. At the annual scale, results show regional patterns in the rainfall‐runoff relationship, associated with the geological age and the local climate. Our results provide evidence of windward/leeward and geological effects on hydrological response at both the annual and flood event scales, with a significant correlation between the event‐scale runoff coefficient and annual rainfall. Combined with a statistical analysis of the data, including the application of a random forest algorithm, results suggest the importance of antecedent saturation conditions, preferentially occurring on the older and more weathered geology, while younger geology displayed a more episodic pattern. This study contributes to increasing our understanding of the hydrological behaviour of tropical volcanic catchments, by analysing the relative importance of climate and geology in controlling the catchments' hydrological response, which may help improve water management and flood prediction
Phenological plasticity and its temperature‐related drivers in common songbirds across Europe
No full textInternational audiencePhenological plasticity—the ability of organisms to adjust the timing of life-history events in response to environmental variability—is the primary adaptive mechanism for many organisms to changing seasonality (e.g., earlier spring). By enabling alignment between life-history events and resource availability, it helps to maintain fitness despite changing environmental conditions. Theory predicts that phenological plasticity should vary among populations because of heterogeneity in environmental variability, and among species because of differences in life-history (e.g., migration distance) and phylogenetic constraints. However, comprehensive, multi-species, and cross-population analyses of phenological plasticity remain scarce. Here, we address this gap by using a unique, four-decade dataset from Europe-wide monitoring of common songbirds. Our approach reveals how variation in phenological plasticity is structured according to site temperature properties, both within and across species. We found that long-distance migrants generally exhibit lower plasticity than residents or short-distance migrants, highlighting a fundamental constraint tied to migration strategy. Within species, populations inhabiting sites with predictable temperature profiles showed slightly stronger plastic responses, particularly among single-brooded species and those adapted to warmer breeding conditions. Notably, populations from the fastest-warming regions demonstrated marginally greater plasticity, regardless of other ecological traits, suggesting a global tendency for increased responsiveness in rapidly changing climates. These findings confirm and extend patterns previously observed at smaller scales, offering a more nuanced understanding of how local temperature conditions drive phenological plasticity. By demonstrating that the interplay between local environmental conditions and life-history traits underpins variation in breeding phenological responses, our study refines the current framework for predicting adaptive potential across populations and species under climate change
Bulletin de veille du réseau d'écotoxicologie terrestre et aquatique N°77
No full textINRAE, réseau ECOTOXBulletin de veille bimestrie
Acute exposure to environmental doses of di-n-butyl phthalate but not di-2-ethylhexyl phthalate induces mortality in isolated and cold-stressed workers of Bombus terrestris L. (Hymenoptera: Apidae)
No full textInternational audienceHighlights: • Exposure to field-realistic doses of DnBP is lethal to ∼25 % of bumblebee workers. • First evidence of NMDRC in bees after exposure to phthalates. • DnBP toxicity is lowered by DEHP in bumblebees at environmental doses. • Low-dose DnBP exposure in B. terrestris workers increase resistance to cold stress. • DnBP toxicity is nullified in a social rearing context.Abstract: Since the past decades, declining trends in bee populations have been reported worldwide. Among multiple anthropogenic factors, endocrine disruptors, such as phthalates, could negatively affect bees and contribute to this decline at environmental level of exposure. Yet, no data are available on phthalate toxicity in bees. Di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DnBP), widely used as plasticisers and adjuvants, are some of the most commonly recorded phthalates in the environment, including on social bee worker cuticles. In this study, we investigated DnBP and DEHP lethal effects on B. terrestris workers after contact exposure to environmentally relevant single-molecule and mixture treatments. Interactions with cold stress and social context were additionally investigated. Firstly, we evidenced for the first time an NMDRC for DnBP toxicity in bees, with an increased mortality of 25 %, 72 h after exposure. By contrast, DEHP did not affect worker survival and even lowered DnBP toxicity when administered as a mixture. Secondly, DnBP at low environmental doses enhanced worker resistance to cold stress, while exposure to cold stress modulated DnBP toxicity, shifting the onset of adverse effects to higher concentrations. Finally, we evidenced that social contacts mitigate DnBP toxicity. Overall, this study provided the first evidence of the detrimental effects caused by these overlooked pollutants on bees, and discusses potential metabolic disruption by phthalate exposure that may affect crucial life traits in bumblebees. Finally, this study highlighted that accounting for complex realistic mixtures and the social context of the studied species seems essential for accurately assessing the toxicity of endocrine disrupting molecules
Field Evidence on Nudging High School Students Towards Pro-Environmental Behavior
No full textInternational audienceThis paper contributes to the literature studying the effect of green nudges on the behavior of young people, particularly adolescents. We conducted a field experiment involving high school students to assess the effectiveness of a nudging strategy which aimed at motivating them to power off computers when these are not used in the classroom. Our nudging strategy resulted in a significant reduction in computer power in the treated high school compared to a control high school. We discuss the relevance of our work for research on young people’s pro-environmental behavior as well as the implications in terms of policy-making
Water consumption of dairy and meat ewes during end of gestation and suckling period
No full textSession 10 - Théâtre 5International audienceFor dairy cows and goats, the French INRAE Feeding System for Ruminants has predictive equations for water consumption. In those equations, the dry matter (DM) intake is the prior factor explaining the total water ingestion. In the goat equation, the other variables considered are milk production and DM and mineral content of the diet. For cows, an additional quantity of drunk water is calculated when the temperature exceeds 15°C. For dairy or meat sheep, there is no equation yet. The present work was performed within a project studying the intake capacity of ewes during end of gestation and suckling period. Within 8 research or school farms, we measured forage intake according to the weight, the physiological stage, the litter size and the hay quality for different breeds.We also measured concentrates and water consumption. The present article synthetizes the water consumption of ewes during the first trials realized in 2023 and 2024 on 5 different farms and on one dairy breed and 4 meat breeds. Each site was equipped with water meters and temperature sensors. Water consumption was recorded daily per group including 6 to 47 animals according to the site. Data were averaged on weekly basis in order to smooth out daily variations. According to the site and the breed, average water consumption varied between 4.6 and 6.9 L per animal per day during end of gestation, and to 7.8 to 10.2 L per animal per day during the suckling period. Based on kilogram of DM consumed, water consumption varied from 2.3 to 3.7 L for end of gestation and from 2.6 to 3.6 L for suckling period. Data observed are coherent regarding usual references (ANSES 2010, INRA 2022). Behind those means, we observed a variability, especially during period with temperature variations and high indoor temperatures. The effect of temperature has not yet been precisely estimated, but subsequent testsshould enable this effect to be approached. CIBRésil project Supported by Casdar founds
Mixing varieties mitigates early root competition in wheat under water and nutrient limitation
No full textInternational audienceCompetition between plants can lead to a tragedy of the commons (TOC), where excessive investment in resourceharvesting organs reduces collective performance. Mixing crop varieties could resolve such TOCs through niche complementarity-if varieties differ in resource use-or selection effects, where competitive varieties benefit from weaker neighbours. While most studies on varietal mixtures focus on above-ground traits, below-ground interactions remain poorly understood. We grew 36 durum wheat (Triticum turgidum ssp. durum) varieties in pure stands and 54 binary mixtures using a high-throughput root phenotyping platform, under both non-limiting (R+) and limiting (R-) water and nutrient conditions, to assess early-stage root competition. In R-, mixtures produced less biomass than expected based on pure stands, largely due to a negative complementarity effect. This was mostly explained by the average projected root area of the two varieties. Rather than indicating a negative interaction, the effect reflected a relaxation of competition: varieties with larger root systems benefited from having weaker competitors, disengaging from the arms race for biomass accumulation. These findings suggest that root area is a promising breeding target for mitigating intra-specific competition and a critical trait for assembling optimal varietal mixtures
Sphingolipid-driven interleaflet coupling orchestrates Rho-GTPase recruitment to nanodomains for signal activation in plants
No full textBiological membranes are both laterally heterogeneous and asymmetrical across leaflets, yet how this asymmetry contributes to signal transduction remains unclear. Here we show that sphingolipid-driven interleaflet coupling coordinates nanodomain organization and Rho-GTPase activation in plants. Using molecular dynamics simulations, super-resolution and single-molecule imaging, quantitative genetics, and biochemistry, we find that very long acyl chain (VLCFA)–containing sphingolipids in the outer leaflet interdigitate with phosphatidylserine (PS) in the inner leaflet, forming a vertical molecular bridge that organizes PS into nanodomains. This coupling promotes recruitment and activation of the Rho-GTPase ROP6 in response to auxin, whereas disruption of VLCFA synthesis or sphingolipid composition disperses PS and ROP6 nanodomains, impairing cytoskeletal reorganization and directional growth. Our findings reveal interleaflet coupling as a fundamental organizing principle linking membrane asymmetry to signaling, providing a conceptual framework for spatial and temporal control of signal transduction across eukaryotic membranes
Water policy in New Caledonia: Participative co-building of water governance in a decolonization process
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/614773/) * Autres projets (id;sigle;titre): ;GOUTTE;(NCL) Gouvernance de l’eau sur terres coutumières//International audienceIn 2018, a few months before the first referendum for full sovereignty, the government of New Caledonia launched the co-design of the country's first water policy based on a broad consultation that involved 1 out of 600 New Caledonians, the locally so-called “Shared Water Policy”. The book both presents and assesses the original and broad participatory process used to build the new water policy. It does so by crossing different points of view (government, local managers and customary authorities). The book is also devoted to bridging the gap between customary land studies and water policy. It seeks a way to weave water representations and customary water management practices into the new policy. This experience in a unique decolonisation complex context will inspire policy makers, academics, managers working on participatory methodologies for more inclusive water policy and governance processes, especially in countries where indigenous populations and legal pluralism orders coexist
Highlighting the services of cattle farming in Madagascar central highlands through a serious game
No full textSession 48 - Théâtre 8International audienceIn Madagascar Central highlands, cattle farming plays a strategic role on family farms, both for its economic value and for the services it provides to the territory, e.g., organic fertilisation production, soil preparation, animal traction or household capital. In the DINAAMICC project, a serious game representing agricultural activities in a typical landscape of the highlands has been built. As part of a participatory approach, it has been used as a tool for analysing and discussing different dynamics on a territorial scale through sessions involving various stakeholders: farmers, stockbreeders, local authorities, technicians. This game highlights the stakes between cattle farming and other agricultural activities in terms of resource allocation, while raising awareness of its importance in the sustainability of agro-sylvo-pastoral systems. A key aspect of the game is the integration of contextual elements specific to local realities, in particular the threat of the Dahalo (cattle thieves). Often regarded as a tradition, livestock theft is a major constraint that weakens farming systems and has a cascading effect: by reducing livestock cattle, it leads to lower supplies of organic fertilizers and a weakening of household capital. By simulating these disruptions, the game enables participants to gain a better understanding of the issues involved in securing livestock production and its effects on the whole farming system. If it is not a tool for political decision-making, the game enables to enlighten debates about importance of livestock farming in family farming and rural areas sustainability