Changing sediment dynamics of a mature backbarrier salt marsh in response to sea-level rise and storm events

© 2018 Schuerch, Dolch, Bisgwa and Vafeidis. Our study analyses the long-term development of a tidal backbarrier salt marsh in the northern German Wadden Sea. The focus lies on the development of the high-lying, inner, mature part of the salt marsh, which shows a striking history of changing sediment dynamics. The analysis of high-resolution old aerial photographs and sampled sediment cores suggests that the mature part of the marsh was shielded by a sand barrier from the open sea for decades. The supply with fine-grained sediments occurred from the marsh inlet through the tidal channels to the inner salt marsh. Radiometric dating ( 210 Pb and 137 Cs) reveals that the sedimentation pattern changed fundamentally around the early-mid 1980s when the sedimentation rates increased sharply. By analyzing the photographic evidence, we found that the sand barrier was breached during storm events in the early 1980s. As a result, coarse-grained sediments were brought directly throug h this overwash from the sea to the mature part of the salt marsh and increased the sedimentation rates. We show that the overwash and the channels created by these storm events built a direct connection to the sea and reduced the distance to the sediment source which promoted salt marsh growth and a supply with coarse-grained sediments. Consequently, the original sediment input from the tidal channels is found to play a minor role in the years following the breach event. The presented study showcases the morphological development of a mature marsh, which contradicts the commonly accepted paradigm of decreasing sedimentation rates with increasing age of the marsh. We argue that similar trends are likely to be observed in other backbarrier marshes, developing in the shelter of unstabilized sand barriers. It further highlights the question of how resilient these salt marshes are toward sea level rise and how extreme storm events interfere in determining the resilience of a mature salt marsh.This study was financially supported by the Deutsche Forschungsgemeinschaft (DFG) through the Cluster of Excellence 80 The Future Ocean, funded within the framework of the Excellence Initiative on behalf of the German federal and state governments, and the personal research fellowship of Mark Schuerch (Project Number 272052902)

Improving livelihoods, training para-ecologists, enthralling children: Earning trust for effective community- based biodiversity conservation in Andasibe, eastern Madagascar

The rainforests of eastern Madagascar are shrinking due to population growth, poverty-driven land degradation and widespread ignorance of ecological dynamics. This has resulted in large-scale transformation and fragmentation of these forests, threatening their unique biodiversity. Many of these problems are also manifest in and around the village of Andasibe. Based on the example of Association Mitsinjo, and drawing from more than a decade of experience of community-based natural resource management in Andasibe, we highlight the challenges and successes of a community-run conservation organization that builds trust through a holistic approach resting on five building blocks: (i) management transfer of natural resources to the local community, (ii) community-based nature tourism, (iii) training of para-scientists, (iv) rainforest restoration and improving local livelihoods, and (v) environmental education. This has resulted in the creation and legal protection of two community-run reserves, Analamazaotra and Torotorofotsy, accompanied by ecological monitoring programs. We illustrate how handing over responsibilities to local communities can be a promising approach to conserving natural resources and biodiversity in Madagascar and elsewhere. La superficie des forêts tropicales de l’est de Madagascar diminue avec la croissance démographique, la dégradation des terres par effet de la pauvreté, ainsi que par l'ignorance générale des interrelations écologiques. Tout cela a abouti à une transformation profonde et étendue ainsi qu’à la fragmentation de ces forêts qui menacent leur biodiversité. Ces problèmes globaux sont pour la plupart rencontrés à la périphérie du village d'Andasibe. Ici, l’exemple de l'Association Mitsinjo est présenté avec plus d’une décennie d’expérience en gestion communautaire des ressources naturelles à Andasibe. Sont ainsi exposés les défis et les succès d'une organisation de conservation gérée par la communauté qui gagne la confiance à travers une approche posée sur cinq piliers]: (i) le transfert de gestion des ressources naturelles à la communauté locale, (ii) l’écotourisme à base communautaire, (iii) la formation de para-scientifiques, (iv) la restauration de la forêt tropicale humide en augmentant les moyens de subsistance des gens vivant sur la périphérie, et (v) l’éducation environnementale. Les actions entreprises ont abouti à la création et la protection efficace de deux réserves gérées par la communauté, accompagnées de programmes de surveillance écologique. Grâce à la responsabilisation des collectivités locales dans la protection de la biodiversité, elles montrent une fierté des actions entreprises qui est un indice prometteur pour la conservation des ressources naturelles et de la biodiversité à Madagascar et ailleurs

Pulsar Scintillation through Thick and Thin: Bow Shocks, Bubbles, and the Broader Interstellar Medium

Observations of pulsar scintillation are among the few astrophysical probes of very small-scale ($\lesssim$ au) phenomena in the interstellar medium (ISM). In particular, characterization of scintillation arcs, including their curvature and intensity distributions, can be related to interstellar turbulence and potentially over-pressurized plasma in local ISM inhomogeneities, such as supernova remnants, HII regions, and bow shocks. Here we present a survey of eight pulsars conducted at the Five-hundred-meter Aperture Spherical Telescope (FAST), revealing a diverse range of scintillation arc characteristics at high sensitivity. These observations reveal more arcs than measured previously for our sample. At least nine arcs are observed toward B1929$+$10 at screen distances spanning $\sim 90\%$ of the pulsar's $361$ pc path-length to the observer. Four arcs are observed toward B0355$+$54, with one arc yielding a screen distance as close as $\sim10^5$ au ($<1$ pc) from either the pulsar or the observer. Several pulsars show highly truncated, low-curvature arcs that may be attributable to scattering near the pulsar. The scattering screen constraints are synthesized with continuum maps of the local ISM and other well-characterized pulsar scintillation arcs, yielding a three-dimensional view of the scattering media in context.Comment: 20 pages, 14 figures. Submitted to MNRAS and comments welcome. Interactive version of Figure 12 available at https://stella-ocker.github.io/scattering_ism3d_ocker202

The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): Spectral Maps of the Asteroid Bennu

The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) is a point spectrometer covering the spectral range of 0.4 to 4.3 microns (25,000-2300 cm-1). Its primary purpose is to map the surface composition of the asteroid Bennu, the target asteroid of the OSIRIS-REx asteroid sample return mission. The information it returns will help guide the selection of the sample site. It will also provide global context for the sample and high spatial resolution spectra that can be related to spatially unresolved terrestrial observations of asteroids. It is a compact, low-mass (17.8 kg), power efficient (8.8 W average), and robust instrument with the sensitivity needed to detect a 5% spectral absorption feature on a very dark surface (3% reflectance) in the inner solar system (0.89-1.35 AU). It, in combination with the other instruments on the OSIRIS-REx Mission, will provide an unprecedented view of an asteroid's surface.Comment: 14 figures, 3 tables, Space Science Reviews, submitte