Global impoverishment of natural vegetation revealed by dark diversity
Anthropogenic biodiversity decline threatens the functioning of ecosystems and the multiple benefits they provide to humanity1. Besides causing species losses in directly affected locations, human influence might also reduce biodiversity in relatively unmodified vegetation if far-reaching anthropogenic effects trigger local extinctions and hinder recolonisation. Here, we show that local plant diversity is globally negatively related to the level of anthropogenic activity in the surrounding region. Impoverishment of natural vegetation was only evident when we considered community completeness: the proportion of all suitable species in the region that are present at a site. To estimate community completeness, we compared the number of recorded species with the dark diversity — ecologically-suitable species that are absent from a site but present in the surrounding region2. In the sampled regions with minimal Human Footprint Index, an average of 35% of suitable plant species were present locally, compared with less than 20% in highly-impacted regions. Besides the potential to uncover overlooked threats to biodiversity, dark diversity also provides guidance for nature conservation. Species in the dark diversity remain regionally present, and their local populations might be restored through measures that improve connectivity between natural vegetation fragments and reduce threats to population persistence.
(Nature. vol. 641, n° 0028-0836, pp. 917-924, 02/04/2025)
U of S, UNIBO, MU / MUNI, CSIC, UV, UC Davis, UC, NINA, UNSW, FUM, NRCan, UAM, JCU, UHasselt, UiB, UPV / EHU, UB, UNCG, UNC, NUM, ESALQ, USP, MMU, UdeS, IPE - CSIC, CSIC, UNIVAQ, UNIPR, EPHE, PSL, LEHNA P3E, LEHNA, UCBL, ENTPE, CNRS, Uninsubria, UR EFNO, INRAE, CEN, UC, CAS, UNESP, HUN-REN, SGGW, ZHAW, CREAF, CSIC, UAB, IMBIV, CONICET, FCEFyN, iDiv, IB-CAS, CAS, UNIBE, TRU, UFRGS, UMR Eco&Sols, Cirad, IRD, INRAE, Institut Agro, UMR ECOFOG, Cirad, UG, CNRS, UA, INRAE, CRBE, IRD, CNRS, Toulouse INP, Comue de Toulouse, EPE UT, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Is the European regulatory model for predicting worker exposure conservative? Comparison of predicted and measured under usual working conditions exposures in fruit growing
Introduction: Pesticide exposure increases the risk of chronic disease among farmers. Understanding exposure is necessary for epidemiological and regulatory purposes. In Europe, worker exposure is assessed during the registration process using the OPEX model, which is based on a limited number of studies, often unpublished and carried out by pesticide companies. We assessed the conservativeness of OPEX for workers performing post-application tasks (re-entry, harvesting).Methods: In 2016-2017, dermal exposure to captan/THPI and dithianon was measured in French fruit farm workers during 65 re-entry (net folding and deployment, thinning, tying) and 58 harvesting days, using patches and cotton gloves. We used linear regression to compare measured and corresponding OPEX-calculated exposure using 1) default parameters; 2) field parameters (actual task duration, measured dislodgeable foliar residues) for 20 observations.Results: Workers were exposed several days after the last application, which is not considered in the pesticide registration process. We found that the model underestimated exposure calculated with field parameters in all observations for dithianon and 60% for captan, linked to an underestimation of OPEX transfer coefficients (ratio of 0.40 for captan and 0.26 for dithianon between default and measured transfer coefficients).Discussion: When observation occurred several days after application, OPEX tended to underestimate exposure. An industry study conducted under controlled working conditions found divergent results. It seems important to include field studies conducted under usual working conditions in the registration process to ensure a truly conservative approach and to consider cumulative exposure, since post-application tasks account for around 600 working hours a year.
(Environmental Research. vol. 271, n° 0013-9351, pp. 121042, 01/04/2025)
UNICAEN Santé, UNICAEN, NU, ANTICIPE, UNICAEN, NU, CHU Caen Normandie, NU, UNICANCER/CRLC, NU, INSERM, BPH, UB, INSERM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LABÉO, ANTICIPE, UNICAEN, NU, CHU Caen Normandie, NU, UNICANCER/CRLC, NU, INSERM, PRISMM, PLATON, UNICAEN, NU, UNICAEN, NU, UNICANCER/CRLC, NU
Chaetoceros Resting Spores Do Not Significantly Bias Sedimentary Diatom‐Bound Nitrogen Isotope Records Despite Distinctly Low Values
Abstract The nitrogen isotopic composition of diatom frustule‐bound organic matter (δ 15 N DB ) is often used to study changes in high latitude biological pump efficiency across glacial‐interglacial cycles, but the proxy may be biased by species‐specific effects. The genus Chaetoceros is of particular interest because of its abundance throughout ocean basins, its shifting biogeography during glacial periods, and the ability of many species to form heavily silicified resting spores. Here we investigate how Chaetoceros resting spores (CRS) record surface nitrate conditions in their nitrogen isotopic composition, and thus impact δ 15 N DB records, using assemblage‐specific sedimentary δ 15 N DB measurements and laboratory culture experiments. We find that fossil CRS from ODP Site 1098 record δ 15 N DB values 1.1–7.8‰ lower than non‐CRS diatoms in sediment. CRS grown in culture yield consistent results, recording δ 15 N DB values 2.6–8.2‰ lower than vegetative Chaetoceros in the same cultures. Low values are attributed to assimilation of isotopically light ammonium, heavy silicification, and/or internal nitrogen allocation processes during sporulation. Applying these findings to published δ 15 N DB records, variable CRS relative abundance in open ocean glacial sediments does not significantly bias δ 15 N DB records across glacial‐interglacial cycles, despite the large δ 15 N DB difference observed in CRS versus non‐CRS diatoms, due to the spores' small size.
(Paleoceanography and Paleoclimatology. vol. 40, n° 2572-4525, 01/04/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Opportunities for Earth observation to inform risk management for ocean tipping points
As climate change continues, the likelihood of passing critical thresholds or tipping points increases. Hence, there is a need to advance the science for detecting such thresholds. In this paper, we assess the needs and opportunities for Earth Observation (EO, here understood to refer to satellite observations) to inform society in responding to the risks associated with ten potential large-scale ocean tipping elements: Atlantic Meridional Overturning Circulation; Atlantic Subpolar Gyre; Beaufort Gyre; Arctic halocline; Kuroshio Large Meander; deoxygenation; phytoplankton; zooplankton; higher level ecosystems (including fisheries); and marine biodiversity. We review current scientific understanding and identify specific EO and related modelling needs for each of these tipping elements. We draw out some generic points that apply across several of the elements. These common points include the importance of maintaining long-term, consistent time series; the need to combine EO data consistently with in situ data types (including subsurface), for example through data assimilation; and the need to reduce or work with current mismatches in resolution (in both directions) between climate models and EO datasets. Our analysis shows that developing EO, modelling and prediction systems together, with understanding of the strengths and limitations of each, provides many promising paths towards monitoring and early warning systems for tipping, and towards the development of the next generation of climate models.
(Surveys in Geophysics. vol. 46, n° 0169-3298, pp. 443–502, 01/04/2025)
MOHC, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], LOCEAN-PROTEO, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, ISMAR, CNR, PIK, GEOMAR, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, JAMSTEC, NPS, GISS, GSFC, OCCR, UNIBE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Enigmatic Deep‐Water Seafloor Depressions East of Tortue Island, Northern Haiti Margin
A widespread area of seafloor depressions -circular, arcuate to elongated-shaped -has been found along the Northern Haitian coast, at water depths between 600 and 2,000 m. Characterized by wavelengths spanning several hundred meters and heights of tens of meters, these depressions are linked with a series of narrow ridges boasting varied morphologies. Our analysis integrating multichannel seismic reflection, highresolution bathymetry data, and sedimentological and geochemical evaluations of surface sediment cores indicates that present-day seafloor morphology results from the interaction of slope bottom currents with the seafloor. The analyzed sediment cores exhibit hemipelagites, silty and sandy contourites, fine-grained turbidites and reworked sand layers, implying sedimentation in a contourite drift system. This is further corroborated by seismic reflection data depicting wavy reflectors and aggradational stacking features typical of contourite drifts. Seafloor depressions are likely erosional features formed on the top of a contourite drift formed by the interaction of bottom currents with an irregular seafloor morphology. The seafloor equilibrium was initially disturbed by mass-wasting events. Subsequently, the quasi-steady flow of along-slope bottom currents influenced sedimentary distribution and controlled the morphology of the seafloor depressions-constant reshaping through erosion on their flanks. The resulting rough seafloor could have facilitated the destabilization of bottom currents and the development of erosive eddies responsible for the current morphology of the seafloor depressions. This study highlights the interplay between sedimentary processes (accumulation and compaction) and bottom currents, showing how their combined effects influence slope sedimentation and seafloor geomorphology, forming unique erosional features.
Plain Language Summary Between 600 and 2,000 m of water depth, the seafloor of the northern Haiti margin presents a field of sub-vertical to elongated depressions. Scientific investigations dealing with the nature of the seafloor material and subsurface structure revealed that such peculiar seafloor morphologies are not related to fluid escape features but to the interplay between sedimentary processes and water masses currents. A submarine landslide triggered in the past has likely created a rough seafloor resulting in the destabilization of currents linked to the deep water masses, enhancing seafloor erosion and deposition.
(Geochemistry, Geophysics, Geosystems. vol. 26, pp. e2024GC012089, 01/04/2025)
iSTeP, INSU - CNRS, SU, CNRS, CY, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFPEN, UCM, UEH
Quantifying the relative contributions of forcings to the variability of estuarine surface suspended sediments using a machine learning framework
The influence of forcing mechanisms on the variability of suspended sediments in an estuary is, for the first time, synoptically quantified over prevailing ('normal') conditions and extreme events. This study investigates the complex and non-linear influence of tides, river discharge, and winds on the variability of suspended sediments in the macrotidal Gironde Estuary, France. Employing a machine learning-based framework, we integrated high-frequency field data, hourly numerical modeling outputs, and semi-daily satellite remote sensing to spatially quantify the relative contributions of forcing mechanisms. Our results reveal that tides are the primary driver of sediment variability (42.3–58.9%), followed by river discharge (21.2–34.7%) and wind (8.7–16.9%). Uncertainties range between 7% and 13.6%. In addition, the spatial variability of their contributions is consistent across numerical modeling and satellite remote sensing data, with differences not exceeding 10%. However, satellite data is limited by cloud cover and may miss extreme events. In contrast, hourly numerical modeling indicates tides are the dominant forcing mechanism under extreme events significantly affecting suspended sediment variability in the estuary. This study verifies the effectiveness of our machine learning approach against traditional Singular Spectral Analysis using field data. We demonstrate that machine learning techniques can effectively synthesize spatial distribution patterns of hydrodynamic and sedimentological variability, including the influence of winds. Our findings highlight not only the potential of satellite observations to analyze prevailing conditions despite data gaps but also that with hourly numerical modeling, the impact of forcings can be synoptically quantified under prevailing ('normal') conditions and extreme events.
(Continental Shelf Research. vol. 287, n° 0278-4343, pp. 105429, 01/04/2025)
DYNECO, IFREMER, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], FURG, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIOZ
Simulating Shoreline and Nearshore Changes: The LX-ST Model
This paper presents LX-ST, a numerical model that simulates shoreline and nearshore evolution over medium-to long-term timescales across diverse sandy coastal environments. It combines the reduced-complexity shoreline model LX-Shore with the shoreface profile translation tool ShoreTrans, enabling it to capture shoreline changes and 3D nearshore morphology. LX-ST accounts for sea-level rise, sediment transport, complex features like artificial structures (e.g., seawalls, groynes), and natural morphologies (e.g., dunes and barriers). The model is tested on synthetic cases, demonstrating its ability to simulate complex coastal configurations. It is then applied to a 5-km beach-dune system in southwest France, which includes a 1.2-km-long seawall. Results show good agreement with observed past shoreline changes and reveal how LX-ST can predict future coastal trajectory shifts, including the eventual retreat and potential disappearance of the beach fronting the seawall. These findings underscore the model's utility in forecasting shoreline
(25/03/2025)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BW-CGC
How scientific networks can help advancing both scientific knowledge and public policies: the case study of the “Plastics, Environment and Health” network
The “Plastics, Environment and Health” research network (groupement de recherche, GDR) created in 2019 gathers the French scientific community working on plastic pollution in all environments (soil, air, water) and their impact on ecosystems and human health. The scientific objective is to rapidly increase knowledge on plastic pollution by supporting collaboration of researchers from different fields such as ecotoxicology, chemistry, physics, microbiology, oceanography and social science. Research is carried out at each stage of the plastic life cycle, (from resource extraction all the way to removal and remediation) and across the entire air-soil-water continuum, integrating transfers of both plastic particles (macro, micro- and nanoplastics) and plastic chemicals (e.g., additives) between different environmental compartments. In this context, the GDR supports the development of multi-scale and transdisciplinary approaches across three main axes: Axis 1 - Air-soil-water continuum: contamination levels and transfer between compartments; Axis 2 - Interactions and transformation of plastics in environmental compartments and living organisms; Axis 3. Plastic pollution risk assessment for ecosystems and human health. To do so, the GDR’s actions focus on (1) training and sharing of scientific knowledge, including developments towards innovation, (2) support for collaboration and interdisciplinarity between network members, (3) dissemination, structuring of the community and its national and international influence, and (4) support for public policy and/or decision-making by strengthening the link between scientists, decision-makers and the plastic industry. To date the research network includes more than 50 laboratories spread across France and over 300 scientists in the field of physics, chemistry, biology, ecology and social sciences. Such a network constitutes a powerful tool to build robust science-based knowledge significantly contributing to the international effort, to disseminate state-of-the-art scientific advances and research priorities needed to tackle plastic pollution to Society and to inform policy makers. This talk will present the French taskforce addressing 'Plastic, Environment, and Health' within the national research network, where the entire community works collaboratively to tackle the urgent challenges of plastic pollution, its environmental consequences, and the associated risks to human health. We will also discuss the importance of building a French-speaking community to support multilingualism in international political science interactions.
(25/03/2025)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, IPREM, UPPA, INC-CNRS, CNRS, MMV, L2C, CNRS, UM, LSAl, ANSES, iEES Paris, IRD, SU, UPEC UP12, CNRS, INRAE, GERS-LEE, ToxAlim, ENVT, Toulouse INP, Comue de Toulouse, Toulouse INP, Comue de Toulouse, INRAE, EPE UT, Comue de Toulouse, EI Purpan, Comue de Toulouse, LOMIC, INSU - CNRS, SU, CNRS, OOB, SU, CNRS, Softmat, INC-CNRS, CNRS, EPE UT, Comue de Toulouse, ICT, IRD, INC-CNRS, CNRS, Toulouse INP, Comue de Toulouse, EPE UT, Comue de Toulouse, IMMM, UM, INC-CNRS, CNRS, IRDL, ENIB, UBO EPE, Bretagne INP, UBS, UBO EPE, CNRS, ENSTA, IP Paris, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR MARBEC, IRD, IFREMER, CNRS, UM
Tide-dominated estuaries as gateways and filters of plastic pollution to the Ocean: insights from the PLASTINEST project
Around three-quarters of oceanic plastic waste come from land-based sources and is mainly transported via rivers and estuaries. However, not all plastics entering estuarine environments reach the open Ocean. Plastic litter and particularly microplastics, can accumulate in estuaries, creating pollution hotspots. This retention may be especially pronounced in macrotidal estuaries, where strong landward residual flows enhance trapping. The ANR PLASTINEST project aims to advance our understanding of the transport, trapping, and dispersion of microplastics within estuarine environments dominated by tides. Using innovative field measurements, controlled physical experiments, and enhanced numerical modeling, PLASTINEST offers new insights into the physical processes that govern particle transport under varying environmental conditions. Ultimately, this research contributes to the ongoing scientific debate on the assessment of plastic river input to the ocean and the existence of a “missing ocean plastic sink”, which to this day ignores the potential trapping role of tide-dominated estuaries. In this work, we present the methodology and key results of PLASTINEST, through three work packages:In the first work package, laboratory experiments provided insights into the erodibility, bottom trapping, and settling dynamics of microplastics in the presence of muddy sediments characteristic of estuarine environments. Both, bottom resuspension and settling behavior were primarily influenced by particles physical properties—shape, density, and size. The presence of cohesive sediment has a secondary influence on microplastics transport in turbid estuaries by increasing the critical shear stress of microplastics deposited on the bed and by promoting flocculation in the water column. These two processes favor the retention and accumulation of particles in turbid estuaries.In work package 2, the spatio-temporal variability of microplastics is evaluated across a macrotidal estuary, in relation to key physico-chemical parameters, through ongoing field campaigns. A novel protocol for sampling microplastics has been implemented in the Gironde estuary, using an innovative in-situ filtration system. Data post-processing will elucidate on the role of hydrodynamics (tides, river discharge, longitudinal tidal and salinity gradient, vertical mixing) on microplastic concentration variability and distribution patterns within the estuary.Numerical modelling tools for the transport of plastic debris were improved to include key microplastic transport processes in work package 3. The implementation of these in the Gironde Estuary provided key insights on the role of environmental factors and transport mechanisms on the trapping and dispersion patterns of microplastics across different temporal scales (from intratidal to seasonal) for floating and sinking particles. Beaching, convergent currents and tidal pumping were identified as key trapping mechanism retaining particles inside the estuary. Interestingly, during wet period, the high river discharge flushes important amount of floating particles into the Ocean , while settling particles remain in the estuary.By synthesizing insights from earlier findings, PLASTINEST will provide a comprehensive view of how plastic particles are transported, accumulate, and are periodically exported to the Ocean within tide-dominated estuarine systems.
(25/03/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UAS, RHITME, Cerema, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, SIAME, UPPA, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, HydEE, Département FTC, PPrime [Poitiers], UP, ISAE-ENSMA, CNRS, UP, Cerema Direction Est, Cerema, CBMN, UB, ENITAB, INC-CNRS, CNRS
A Common Terminology to Unify Research and Conservation of Coralline Algae and the Habitats They Create
Linguistic uncertainty is a prime source of uncertainty pervading ecology and conservation. Coralline algae are a widespread and diverse group of calcifying red macroalgae that underpin coastal ecosystem function and service provision. Recent increasing interest in coralline algae in the scientific literature has revealed a diverse but confusing terminology at organism to habitat scales. Coralline algal research and conservation are international and multidisciplinary, so there are geographic and disciplinary imbalances in research and conservation efforts. To reach consensus and reduce uncertainty, we propose a unified terminology. We review trends in cultural and scientific use of coralline algal terms and propose a system based on six morphologies: (1) attached, (2) free‐living geniculate, (3) encrusting and free‐living nongeniculate coralline algae, the latter either being (4) nucleated or (5) non‐nucleated thalli or (6) fragments. We take inspiration from other coastal systems that have achieved consensus through umbrella terms, such as ‘coral’ and ‘kelp’, to accelerate global progress in coralline algal research and conservation. We characterise 14 coralline algae–dominated habitat global types, falling within seven functional groups, four biomes and four realms: (1) freshwater coralline streams; (2) coralline tide pools; (3) intertidal coralline rims and (4) turf; (5) coralline sea caves; (6) coral–algal reefs; (7) algal ridges; (8) coralligenous reefs; subtidal (9) carbonate crusts, (10) coralline barrens and (11) turf; and (12) articulith, (13) maerl and (14) rhodolith beds, which fall into the coralline algal bed functional group. We hope this unified terminology promotes data comparison, enables cross‐boundary and cross‐sector sharing of best practices, develops capacity for meta‐analyses and improves conservation strategies.
(Aquatic Conservation: Marine and Freshwater Ecosystems. vol. 35, n° 1052-7613, 24/03/2025)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, UFRJ, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, DYNECO, IFREMER, UGR, NHM, CDPQ, INTECHMER, Cnam, LUSAC, UNICAEN, NU, IMR, UiB, UDC, UAlg, FIOCRUZ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS