Cartographie automatisée des zones à hauts risques naturels par superposition de données multivariées : exemple de la commune de Seillans (Var)

Mémoire HS n° 15 - Géologie Alpine Risques naturels dans le Sud-est de la France - Colloque Association des Géologues du Sud-est - Avignon, 19 et 20 octobre 1989Dans le cadre d'une étude financée par l'EPR PACA, nous avons développé une méthode de cartographie des zones soumises à des mouvements du sol, à l'aide de moyens infonnatiques. Nous avons appliqué cette méthode à la commune de Seillans afin d'intégrer cette carte des risques dans le plan d'occupation des sols. Parmi les phénomènes naturels qui contraignent l'utilisation du sol, nous n'avons pris en compte que le phénomène glissement de terrain : il n'est en effet pas encore possible par les méthodes employées de mettre en évidence les zones soumises à des phénomènes de dissolution; nous avons également laissé de coté le risque lié à l'instabilité des falaises et des chutes de blocs. Pour réaliser cette cartographie des zones soumises à des mouvements de sol, nous avons retenu trois facteurs: - nature lithologique des terrains affleurant, - pente topographique et sa valeur en pourcentage - hydrologi

Indeterminate status of West African populations of inshore common bottlenose dolphins <i>Tursiops truncatus</i> caution against opportunistic live-capture schemes

The limited information available on the status of inshore common bottlenose dolphins Tursiops truncatus along the coasts of West Africa is reviewed. Although reported from at least ten countries, it is unclear whether their distribution is continuous. Population structure and genetics have not been studied, however cranial morphology suggests that the West African dolphins differ from North Sea bottlenose dolphins. Mean group sizes are small (3.19 – 12.91 individuals/group) and are smallest in Guinea-Bissau. There are no estimates of abundance but by analogy with a well-studied population in Sarasota, Gulf of Mexico, the Guinea-Bissau population may number only in the hundreds. It is essential that scientific estimates be obtained through dedicated surveys. In some areas of Guinea-Bissau with a high density of fishing activities, bottlenose dolphins are now less frequently encountered than they were in the recent past. Key parameters besides abundance, including population identity, bycatch levels and other anthropogenic threats need to be documented and quantified before any deliberate exploitation is considered. A small-scale, botched live-capture operation in Senegal in 2003, in which all dolphins died, serves as warning against such opportunistic schemes. In management terms, live-capture operations are equivalent to hunting and multi-year, large-scale removals of bottlenose dolphins in Guinea-Bissau would have the potential to effectively extirpate the wild population from its waters

Human transformations of the Wadden Sea ecosystem through time: a synthesis

Todayrsquos Wadden Sea is a heavily human-altered ecosystem. Shaped by natural forces since its origin 7,500 years ago, humans gradually gained dominance in influencing ecosystem structure and functioning. Here, we reconstruct the timeline of human impacts and the history of ecological changes in the Wadden Sea. We then discuss the ecosystem and societal consequences of observed changes, and conclude with management implications. Human influences have intensified and multiplied over time. Large-scale habitat transformation over the last 1,000 years has eliminated diverse terrestrial, freshwater, brackish and marine habitats. Intensive exploitation of everything from oysters to whales has depleted most large predators and habitat-building species since medieval times. In the twentieth century, pollution, eutrophication, species invasions and, presumably, climate change have had marked impacts on the Wadden Sea flora and fauna. Yet habitat loss and overexploitation were the two main causes for the extinction or severe depletion of 144 species (~20% of total macrobiota). The loss of biodiversity, large predators, special habitats, filter and storage capacity, and degradation in water quality have led to a simplification and homogenisation of the food web structure and ecosystem functioning that has affected the Wadden Sea ecosystem and coastal societies alike. Recent conservation efforts have reversed some negative trends by enabling some birds and mammals to recover and by creating new economic options for society. The Wadden Sea history provides a unique long-term perspective on ecological change, new objectives for conservation, restoration and management, and an ecological baseline that allows us to envision a rich, productive and diverse Wadden Sea ecosystem and coastal society

ESR studies on some spiropyrans, spironaphthopyrans, and spirooxazines

Biradicals were double-trapped by bubbling NO through benzene solutions of some photochromic spirocompounds; it would however appear that these species do not directly participate in the photochromic process. The ESR spectra of the radical anions of some nitrosubstituted spirocompounds indicated that there is no electronic interaction between the two moieties of the spiromolecules; reducing the substrates in the absence or in the presence of light leads to different ESR signals, but it cannot be excluded that the observed differences are only due to the different reaction media

Spectroscopic characterisation and photodegradation studies of photochromic spiro[fluorene-9,3′-[3′H]-naphtho[2,1-b]pyrans]

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