Ecologie de la conservation des écosystèmes halophiles de Camargue, en particulier des sansouïres

Les steppes halophiles méditerranéennes à salicornes vivaces (Sarcocornia fruticosa, Arthrocnemum macrostachyum) de Camargue, les sansouires, ont été étudiées dans les processus spatio-temporels de leur distribution aux fins de leurs conservation. Cette étude se place dans une démarche d'écologie de la conservation, c'est-à-dire dans une recherche globalisante du problème posé par la régression d'un écosystème. La distribution exacte des différentes associations végétales de ces écosystèmes a pour cela été intégrée dans la base de données d'un système d'information géographique (SIG) en associant aux objets de la base des caractéristiques telles que la propriété foncière et la gestion hydraulique. Grâce aux inventaires, nous avons pu montrer que ces écosystèmes sont affectés dans leur superficie totale et dans leur diversité spécifique et intercommunautaire. Les processus de destruction des sansouïres qui ont été identifiés révèlent une diversification à laquelle le statut juridique de ces écosystèmes n'est que peu adapté. L'étude de la perception de ces écosystèmes à travers des entretiens semi-dirigés ainsi que la littérature, atteste de l'attachement de la société, camarguaise ou de passage, et du fait qu'il existe une attente forte pour leur conservation. La conservation de ces écosystèmes pose pourtant des problèmes dans le cadre privé du fait de leur faible rentabilité face à celle des marais de chasse vers lesquels leur conversion est facilitée par le système hydraulique camarguais. Les mesures agri-environnementales mises en place depuis quelques années peuvent apporter une partie de la réponse à leur régression, mais le problème de leur statut réglementaire doit encore être révisé afin de se donner les outils de leur protection. Dans la perspective de rachats publics de terrains en Camargue, nous avons avancé l'idée que les sansouires constituent un milieu indicateur de naturalité dans ce territoire, et des critères de priorité pour leur conservation ont été définis.The mediterranean halophytic shrublands of perenial salicorns (Sarcocornia fruticosa, Arthrocnemum macrostachyum) have been studied in Camargue, especially in their spatiotemporal distribution dynamics, in the perspectives of their conservation. In a conservation ecology approach, this is a globalizing research based on the environmental problem caused by the destruction of this ecosystem. The exact distribution of the vegetal communities has been integrated in the data base of a geographical information system (GIS). Thanks to the inventories, we have been able to find out that these ecosystems are affected not only in their total distribution, but also in their specific and intercommunity diversity. The destruction processes of these communities which have been identified reveal a temporal divesification that the misadapted legislative status cannot efficiently fight. The perception of these ecosystems was also studied, through semi-directed interviews as well as existing litterature, and showed a strong social attachment to these ecosystems, from the locals and from the tourists. Nevertheless, their conservation in the private ownership sets problems due to their feable rentability, compared to hunting marshes. The conversion of the halophytic shrublands into hunting marshes, facilated by the expanded water management system existing in Camargue, is the actual main threat to the maintenance of these. Agri-environmental measures have been adopted by some landowers since a few years, and may partly answer to the problem of their conservation through financial motivations, but the revision of their reglementary status has to be revised to insure their protection on the long-term. In the perspective of future public acquisitions in Camargue, we have advanced the idea that these halophytic shrublands constitute a indicator ecosystem of the naturalness in this territory, and have set priority criterias for their conservation.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Tackling Invasive Alien Species in Europe: the Top 20 Issues

Globally, Invasive Alien Species (IAS) are considered to be one of the major threats to native biodiversity, with the World Conservation Union (IUCN) citing their impacts as ‘immense, insidious, and usually irreversible’. It is estimated that 11% of the c. 12,000 alien species in Europe are invasive, causing environmental, economic and social damage; and it is reasonable to expect that the rate of biological invasions into Europe will increase in the coming years. In order to assess the current position regarding IAS in Europe and to determine the issues that were deemed to be most important or critical regarding these damaging species, the international Freshwater Invasives - Networking for Strategy (FINS) conference was convened in Ireland in April 2013. Delegates from throughout Europe and invited speakers from around the world were brought together for the conference. These comprised academics, applied scientists, policy makers, politicians, practitioners and representative stakeholder groups. A horizon scanning and issue prioritization approach was used by in excess of 100 expert delegates in a workshop setting to elucidate the Top 20 IAS issues in Europe. These issues do not focus solely on freshwater habitats and taxa but relate also to marine and terrestrial situations. The Top 20 issues that resulted represent a tool for IAS management and should also be used to support policy makers as they prepare European IAS legislation