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On the relative role of abiotic and biotic controls on channel network development: insights from scaled tidal flume experiments
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Tidal marshes provide highly valued ecosystem services, which depend on variations in the geometric properties of the tidal channel networks dissecting marsh landscapes. The development and evolution of channel network properties are controlled by abiotic (dynamic flow-landform feedback) and biotic processes (e.g., vegetation-flow-landform feedback). However, the relative role of biotic and abiotic processes, and under which condition one or the other is more dominant, remains poorly understood. In this study, we investigated the impact of spatio-temporal plant colonization patterns on tidal channel network development through flume experiments. Four scaled experiments mimicking tidal landscape development were conducted in a tidal flume facility: two control experiments without vegetation, a third experiment with hydrochorous vegetation colonization (i.e., seed dispersal via the tidal flow), and a fourth with patchy colonization (i.e., by direct seeding on the sediment bed). Our results show that more dense and efficient channel networks are found in the vegetation experiments, especially in the hydrochorous seeding experiment with slower vegetation colonization. Further, an interdependency between abiotic and biotic controls on channel development can be deduced. Whether biotic factors affect channel network development seems to depend on the force of the hydrodynamic energy and the stage of the system development. Vegetation-flow-landform feedbacks are only dominant in contributing to channel development in places where intermediate hydrodynamic energy levels occur and mainly have an impact during the transition phase from a bare to a vegetated landscape state. Overall, our results suggest a zonal domination of abiotic processes at the seaward side of intertidal basins, while biotic processes dominate system development more towards the landward side.
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RBINS Staff Publications 2024
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Mangroves as nature-based mitigation for ENSO-driven compound flood risks in a river delta
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Densely populated coastal river deltas are very vulnerable to compound flood risks, coming from both oceanic and riverine sources. Climate change may increase these compound flood risks due to sea level rise and intensifying precipitation events. Here, we investigate to what extent nature-based flood defence strategies, through conservation of mangroves in a tropical river delta, can contribute to mitigate the oceanic and riverine components of compound flood risks. While current knowledge of estuarine compound flood risks is mostly focussed on short-term events such as storm surges (taking one or a few days), longer-term events, such as El Niño events (continuing for several weeks to months) along the Pacific coast of Latin America, are understudied. Here, we present a hydrodynamic modelling study of a large river delta in Ecuador aiming to elucidate the compound effects of El Niño driven oceanic and riverine forcing on extreme high water level propagation through the delta, and in particular, the role of mangroves in reducing the compound high water levels. Our results show that the deltaic high water level anomalies are predominantly driven by the oceanic forcing but that the riverine forcing causes the anomalies to amplify upstream. Furthermore, mangroves in the delta attenuate part of the oceanic contribution to the high water level anomalies, with the attenuating effect increasing in the landward direction, while mangroves have a negligible effect on the riverine component. These findings show that mangrove conservation and restoration programs can contribute to nature-based mitigation, especially the oceanic component of compound flood risks in a tropical river delta.
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RBINS Staff Publications 2024
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A global meta-analysis on the drivers of salt marsh planting success and implications for ecosystem services
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Planting has been widely adopted to battle the loss of salt marshes and to establish living shorelines. However, the drivers of success in salt marsh planting and their ecological effects are poorly understood at the global scale. Here, we assemble a global database, encompassing 22,074 observations reported in 210 studies, to examine the drivers and impacts of salt marsh planting. We show that, on average, 53% of plantings survived globally, and plant survival and growth can be enhanced by careful design of sites, species selection, and novel planted technologies. Planting enhances shoreline protection, primary productivity, soil carbon storage, biodiversity conservation and fishery production (effect sizes = 0.61, 1.55, 0.21, 0.10 and 1.01, respectively), compared with degraded wetlands. However, the ecosystem services of planted marshes, except for shoreline protection, have not yet fully recovered compared with natural wetlands (effect size = −0.25, 95% CI −0.29, −0.22). Fortunately, the levels of most ecological functions related to climate change mitigation and biodiversity increase with plantation age when compared with natural wetlands, and achieve equivalence to natural wetlands after 5–25 years. Overall, our results suggest that salt marsh planting could be used as a strategy to enhance shoreline protection, biodiversity conservation and carbon sequestration.
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RBINS Staff Publications 2024
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Vegetation controls on channel network complexity in coastal wetlands
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Channel networks are key to coastal wetland functioning and resilience under climate change. Vegetation affects sediment and hydrodynamics in many different ways, which calls for a coherent framework to explain how vegetation shapes channel network geometry and functioning. Here, we introduce an idealized model that shows how coastal wetland vegetation creates more complexly branching networks by increasing the ratio of channel incision versus topographic diffusion rates, thereby amplifying the channelization feedback that recursively incises finer-scale side-channels. This complexification trend qualitatively agrees with and provides an explanation for field data presented here as well as in earlier studies. Moreover, our model demonstrates that a stronger biogeomorphic feedback leads to higher and more densely vegetated marsh platforms and more extensive drainage networks. These findings may inspire future field research by raising the hypothesis that vegetation-induced self-organization enhances the storm surge buffering capacity of coastal wetlands and their resilience under sea-level rise.
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RBINS Staff Publications 2024
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Mangrove ecosystem properties regulate high water levels in a river delta
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Intertidal wetlands, such as mangroves in the tropics, are increasingly recognized for their role in nature-based mitigation of coastal flood risks. Yet it is still poorly understood how effective they are at attenuating the propagation of extreme sea levels through large (order of 100 km2) estuarine or deltaic systems, with complex geometry formed by networks of branching channels intertwined with mangrove and intertidal flat areas. Here, we present a delta-scale hydrodynamic modelling study, aiming to explicitly account for these complex landforms, for the case of the Guayas delta (Ecuador), the largest estuarine system on the Pacific coast of Latin America. Despite coping with data scarcity, our model accurately reproduces the observed propagation of high water levels during a spring tide. Further, based on a model sensitivity analysis, we show that high water levels are most sensitive to the mangrove platform elevation and degree of channelization but to a much lesser extent to vegetation-induced friction. Mangroves with a lower surface elevation, lower vegetation density, and higher degree of channelization all favour a more efficient flooding of the mangroves and therefore more effectively attenuate the high water levels in the deltaic channels. Our findings indicate that vast areas of channelized mangrove forests, rather than densely vegetated forests, are most effective for nature-based flood risk mitigation in a river delta.
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RBINS Staff Publications 2024
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New specimens and CT data of the longirostrine crocodylian Thoracosaurus isorhynchus from the Maastrichtian of Mont-Aimé (Paris Basin, France)
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Thoracosaurs are a polyphyletic group of Cretaceous–Paleogene longisrostrine crocodylians from Europe and North America. Traditionally perceived as gavialoids, phylogenetically closer to Gavialinae than to Tomistominae, they play a key role in the gharial problem: their old age and seemingly close relationship to Gavialinae is inconsistent with molecular clock estimates indicating a far younger origin of Gavialoidea. Moreover, the phylogenetic position of thoracosaurs is debated, as recent studies suggested thoracosaurs are non-crocodylian eusuchians instead. Here we describe thoracosaur material from Mont-Aimé, France, rediscovered in the collections of the Musée d’Histoire Naturelle de Lille. The Mont-Aimé is famous for its richness in fossil vertebrates, among which the longirostrine species Thoracosaurus isorhynchus (formerly T. macrorhynchus). Confusion about the age of the vertebrate layers has recently been solved, indicating that they are Maastrichtian in age instead of Danian. The new material most likely belongs to T. isorhynchus based on a flexure in the ectopterygoid–pterygoid suture, a distinctive character found in adults of this taxon. Our study reveals new characters not visible on previously known material. An example is the short posterior non-dentigerous process of the maxilla, a character shared with early Paleogene longirostrines and tomistomines but not with gavialines. Furthermore, microCT data of the skull reveal for the first time endocranial characters of this taxon, such as the presence of an internal recess in the parietal. Together with redescribed T. isorhynchus material from the Muséum d’Histoire Naturelle, Paris, this leads to an updated phylogenetic position of this taxon.
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RBINS Staff Publications 2023
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Locomotor behavior of Paleocene mammals: Insights from the semicircular canals of the inner ear
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The end-Cretaceous mass extinction triggered the collapse of ecosystems and a drastic turnover in mammalian communities leading to the demise of many ecologically specialized species. While Mesozoic mammals were ecomorphologically diverse, recognizable ecological richness was only truly established in the Eocene. Questions remain about the ecology of the first wave of mammals radiating after the extinction. Here, we use the semicircular canals of the inner ear as a proxy for locomotor behavior. Thirty new inner ear virtual endocasts were generated using high-resolution computed tomography scanning. This sample was supplemented by data from the literature to construct a dataset of 79 fossils spanning the Jurassic to the Eocene alongside 262 extant mammals. Vestibular sensitivity was measured using the radius of curvature against body mass and the residuals of this relationship were analyzed. The petrosal lobule size relative to body mass were compared with the inner ear data as they have a role in maintaining gaze stabilization during motion. Paleocene mammals exhibited smaller canal radius of curvature, compared to Mesozoic, Eocene, and extant taxa. In the early Paleocene, canal radius and associated petrosal lobules were relatively smaller on average compared to other temporal groups, suggesting less ability for fast movements. Our results support previous work on tarsal morphology and locomotor behavioral ancestral state reconstructions suggesting that ground dwelling mammalian species were more common than arboreal taxa during the Paleocene. Ultimately, this may indicate that the collapse of forested environments immediately after extinction led to the preferential survivorship of more terrestrially adapted mammals.
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RBINS Staff Publications 2023
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Biofluorescence of the Mottled shovel-nosed frog, Hemisus marmoratus: first report for Hemisotidae.
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RBINS Staff Publications 2023
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Philine angulata (Jeffreys, 1867) (Gastropoda, Cephalaspidea: Philinidae) collected for the first time in Icelandic waters
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RBINS Staff Publications 2024
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Recommendations from the MARPOL Annex VI Working Groups on regulations regarding air pollution from ships. Document presented by the co-convenors of the SOWG (France and the Netherlands) and the TWG (Belgium and Germany) at the Meeting of the Working Grou
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