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Same data, different analysts: variation in effect sizes due to analytical decisions in ecology and evolutionary biology
No full textInternational audienceAlthough variation in effect sizes and predicted values among studies of similar phenomena is inevitable, such variation far exceeds what might be produced by sampling error alone. One possible explanation for variation among results is differences among researchers in the decisions they make regarding statistical analyses. A growing array of studies has explored this analytical variability in different fields and has found substantial variability among results despite analysts having the same data and research question. Many of these studies have been in the social sciences, but one small "many analyst" study found similar variability in ecology. We expanded the scope of this prior work by implementing a large-scale empirical exploration of the variation in effect sizes and model predictions generated by the analytical decisions of different researchers in ecology and evolutionary biology. We used two unpublished datasets, one from evolutionary ecology (blue tit, Cyanistes caeruleus, to compare sibling number and nestling growth) and one from conservation ecology (Eucalyptus, to compare grass cover and tree seedling recruitment). The project leaders recruited 174 analyst teams, comprising 246 analysts, to investigate the answers to prespecified research questions. Analyses conducted by these teams yielded 141 usable effects (compatible with our meta-analyses and with all necessary information provided) for the blue tit dataset, and 85 usable effects for the Eucalyptus dataset. We found substantial heterogeneity among results for both datasets, although the patterns of variation differed between them. For the blue tit analyses, the average effect was convincingly negative, with less growth for nestlings living with more siblings, but there was near continuous variation in effect size from large negative effects to effects near zero, and even effects crossing the traditional threshold of statistical significance in the opposite direction. In contrast, the average relationship between grass cover and Eucalyptus seedling number was only slightly negative and not convincingly different from zero, and most effects ranged from weakly negative to weakly positive, with about a third of effects crossing the traditional threshold of significance in one direction or the other. However, there were also several striking outliers in the Eucalyptus dataset, with effects far from zero. For both datasets, we found substantial variation in the variable selection and random effects structures among analyses, as well as in the ratings of the analytical methods by peer reviewers, but we found no strong relationship between any of these and deviation from the meta-analytic mean. In other words, analyses with results that were far from the mean were no more or less likely to have dissimilar variable sets, use random effects in their models, or receive poor peer reviews than those analyses that found results that were close to the mean. The existence of substantial variability among analysis outcomes raises important questions about how ecologists and evolutionary biologists should interpret published results, and how they should conduct analyses in the future
Patrimoines alimentaires en Amérique latine. Faire face aux inégalités et aux changements globaux : introduction.
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En-échelon Rifting and Origin of the Volcanism in the Comoros
No full textInternational audienceTwo volcanic provinces have been recently discovered during the SISMAORE oceanographic cruise in the Comoros archipelago in the North Mozambique Channel between Madagascar and East Africa: N'Droundé, along the North-eastern insular slopes of Grande Comores Island and Mwezi, in the abyssal plain, north-east of Mayotte and Anjouan islands. By combining bathymetry and backscatter data, high-resolution seismic reflection and sub-bottom profiles, we have identified and mapped various tectonic (faults, forced folds) and volcanic structures (lava flows, edifices, sills, dykes) at several spatial scales on the seabed and in crosssection within the sedimentary cover. We have characterized the volcano-tectonic structures (geometry, segmentation, and kinematics) to better understand the link (geometry, chronology) between tectonic and volcanic processes. We show that volcanic and tectonic features are controlled by tectonic processes and viceversa. Ridges, volcanic cones and lava flows are set up along fissures and dikes during main rifting events to accommodate a N40°E regional extension within an E-W right lateral shear transfer zone. The volcano tectonic features are Plio-Pleistocene. This transfer zone lies between the offshore branch of the East African rift system and Malagasy grabens and may have formed when the East African rifts propagated offshore. We evidence a major rifting episode in the last Ma. The estimated volume and flux of extruded lavas show that the volcanism of the Comoros could be related to shallow tectonic processes
Impacts of the closure of the Mozambique Channel on the southwest Indian Ocean circulation: A regional numerical simulation
No full textInternational audiencePaleobathymetric reconstructions suggest that 35 million years ago, local uplift of the Davie Ridge could have temporarily raised a continental land-bridge between Africa and Madagascar and dramatically affected their connectivity. Numerical simulations of a regional model of the southwest Indian Ocean at mesoscale resolution are performed to investigate the consequences of such a closure of the Mozambique Channel. Compared to a reference simulation of present day circulation, blocking the Mozambique Channel results in a redistribution of the transport around Madagascar dramatically strengthening the East Madagascar Current and eddy variability south of Madagascar, broadening the Agulhas Current, and modifying water mass properties and bottom circulation.</div
Historical human impact on the endangered, relict and iconic Canary Islands dragon tree (Dracaena draco (L.) L.) and its uncertain fate in the face of climate change
No full textInternational audienceMacaronesian oceanic islands harbour the emblematic relict Canary Islands dragon tree (D. draco (L.) L. subsp. draco, Asparagaceae). Historical records suggest that its populations, nowadays restricted to Tenerife and Gran Canaria islands (Canaries) and Madeira Island, had a much wider geographic range in the past. In this study, we aimed at (i) testing whether current D. draco subsp. draco populations are relicts of a former wider distribution because of human impact, (ii) whether those populations are at risk with future climate change and (iii) targeting priority zones for in situ conservation face to global changes. We based our approach on the comparison between actual distribution, land use data and suitable area modelled via Environmental Niche Models (ENM) and projected under future climate change scenarios. ENM were calibrated at two different phylogenetic levels to account for taxonomic uncertainties. We found that: (i) The Canary Islands dragon tree populations occupy only 3-4% of their suitable area, reflecting their relict status due to past habitat alteration and overexploitation; (ii) Their response to future climate change varies depending on ENMs and climate change scenarios, but some projections suggest that climate may become unsuitable within their actual distribution range; (iii) Finally, we provide a map of zones to prioritize, specifically semi-natural areas predicted to remain suitable in the future, for in situ recovery operation
Impacts of post-disaster restoration projects on communities and their environment through the landscape
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Eoldist , a Web Application for Estimating Cautionary Detection Distance of Birds by Automatic Detection Systems to Reduce Collisions With Wind Turbines
No full textInternational audienceThe installation of automatic detection systems (ADSs) on operating wind energy facilities is a mitigation measure to reduce bird collisions. The effectiveness of an ADS depends on a combination of parameters, including the detection distance of the bird, its flight speed, and the time to complete the chosen action (e.g., turbine shutdown). We created a web application, Eoldist , to calculate cautionary detection distances required by an ADS, using bird flight speed and turbine shutdown time as input parameters. We compiled a database of the flight speeds of 168 Western Palearctic birds from a review of scientific literature supplemented by an analysis of unpublished GPS‐tracking datasets. To estimate turbine shutdown time, we conducted 137 field trials of experimental shutdown at seven wind farms and found that the duration to reach residual rotor speeds of 3 or 2 rotations per minute (rpm) was respectively 32.2 or 38.8 s on average. Based on this data, Eoldist allows the user to select a species from the database, wind turbine characteristics, and a residual rotor speed (3 or 2 rpm); it then calculates the time to reach the selected threshold and provides a distribution curve for the cautionary detection distance needed to prevent collision. This article includes examples of cautionary detection distances required for several species to demonstrate the sensitivity of key input parameters. Eoldist is freely available and should help the wind energy industry, ADS suppliers, and environmental agencies to define requirements for ADS bird detection that are compatible with the biology of the target species
RECONSTRUCTING EARLIEST DIAGENESIS CONDITION USING SEDIMENTO LOGICAL AND GEOCHEMICAL CHARACTERISTICS OF GLAUCONITES . APPLICATION TO LIMESTONEMARLSTONE ALTERNATION IN THE BOULONNAIS
No full textInternational audienceSome of the geological formations of Upper Jurassic and Cretaceous age in the Boulonnais area (Strait of Pas-de-Calais, English Channel) show levels relatively rich in glauconite (a few weight% to 44 wt%). Recent works have shown that glauconite could have formed during (very) early diagenesis; this authigenic phyllosilicate could have thus witnessed the chemical conditions prevailing at the sediment-water interface or a short distance below it. This can be of particular interest in the case of the Assises de Croï Formation showing alternating carbonate beds and marly beds. The beds are of early diagenetic origin and contain populations of glauconite grains which formed even earlier. Glauconite can therefore be considered here as the privileged proxy to the sediment-water interface conditions during the development of the limestone-marl alternation, which is a common pattern in the sedimentary record worldwide. Glauconite was observed from the perspective of its chemical composition (including REE) as well as that of the particle size distribution. The results show that, if redox-proxying trace elements such as V, As, Ge can reflect the redox status of the conditions in which glauconite was formed, this is not the case for REE. The only parameter linked to REE which provides paleoenvironmental indications here is ∑REE, being negatively correlated with the sedimentation rate. It is suggested that REE were all the more incorporated to glauconite when the sedimentation rate was low, but without any appreciable fractionation among REE. Concerning the limestone/marl alternation, our results show that its development is linked neither to variations in redox conditions nor to hydrodynamic changes of the depositional environment. This is a diagenetic phenomenon, the cause of which remains to be determined. Finally, a relationship could be highlighted between the sedimentation rate and the size of the glauconite grains grown in situ.Les formations géologiques du Jurassique supérieur et du Crétacé du Boulonnais (détroit du Pas-de-Calais) peuvent présenter des teneurs notables en grain de glauconite (de quelques % pondéraux à 44 %). Des travaux récents ont montré que cette glauconite s'est formée au cours de la diagenèse (très) précoce ; ce phyllosilicate authigénique aurait ainsi pu être le témoin des conditions paléo-environnementales -en particulier, chimiques -régnant à l'interface eau-sédiment ou à une courte distance au-dessous. Ceci peut être particulièrement intéressant dans le cas des Assises de Croï présentant une alternance de bancs carbonatés et d'interbancs marneux. Les bancs carbonatés sont d'origine diagénétique précoce et contiennent des populations de grains de glauconite qui se sont formés encore plus tôt. La glauconite peut donc être considérée ici comme l'indicateur privilégié des conditions d'interface eau-sédiment lors du développement de l'alternance calcaire-marne, qui est un faciès commun dans les archives sédimentaires mondiales. La glauconite a été observée du point de vue de sa composition chimique (y compris les Terres Rares) ainsi que de celui de la distribution de la taille des particules. Les résultats montrent que, si des éléments-traces tels que V, As, Ge peuvent refléter le statut redox des conditions dans lesquelles la glauconite s'est formée, ce n'est pas le cas pour les TerresRares. Le seul paramètre lié aux Terres Rares qui fournisse ici des indications paléoenvironnementales est ∑REE, qui est manifestement lié à la vitesse de sédimentation. Il est suggéré que les Terres Rares étaient d'autant plus incorporées à la glauconite que le taux de sédimentation était faible, mais sans fractionnement visible au sein des Terres Rares elles-mêmes. Par ailleurs, concernant les alternances, nos résultats montrent que leur évolution n'est liée ni aux variations des conditions redox ni à celles de l'hydrodynamique du milieu de dépôt. Il s'agit d'un phénomène principalement diagénétique dont la cause reste à déterminer (la condensation sédimentaire est une cause probable ; J. -F. Deconinck, communication personnelle, 2024). Enfin, une relation a pu être mise en évidence entre la vitesse de sédimentation et la taille des grains de glauconite développés in situ : une relative condensation sédimentaire accompagne une augmentation de la taille des grains de glauconite. Au total, les grains de glauconite peuvent avoir une vraie valeur d'indicateur paléo-environnemental, à condition que leurs conditions de formation aient été bien définies.</div
Surface circulation characterization along the middle southern coastal region of Vietnam from high-frequency radar and numerical modeling
No full textInternational audienceCoastal water dynamics along the Vietnamese middle southern coast (VMSC) region, part of the South China Sea, are highly complex with large spatiotemporal variability whose drivers are not yet well understood. For the first time, high-resolution surface current data from highfrequency radar (HFR) measurements were obtained in this region during the early (transition) phase of the Asian summer monsoon. The data were used for comparison with simulation results from a circulation model, SYMPHONIE, and ultimately to optimize the wind forcing in the model. Both modeling and HFR were able to show the spatial and temporal evolution of the surface circulation, but some discrepancies were found between model and HFR data on some days, coinciding with the evolution of the wind. Two methods were used to optimize the wind forcing, namely the ensemble perturbation smoother (EnPS) and the wind correction method using wind-driven surface currents (EkW). Both methods achieved a significant reduction (∼ 36 %-40 %) in the error of the surface current velocity fields compared to the measured data. Optimized winds obtained from the two methods were compared with satellite wind data for validation. The results show that both optimization methods performed better in the far field, where topography no longer affects the coastal surface circulation. The optimization results revealed that the surface circulation is driven not only by winds but also by other factors such as intrinsic ocean variability, which is not entirely controlled by boundary conditions. This indicates the potential usefulness of large velocity datasets and other data fusion methods to effectively improve modeling results