A Bayesian framework to objectively combine metrics when developing stressor specific multimetric indicator

In the context of the European Water Framework Directive (WFD), monitoring programs and related indicators have been developed to assess anthropogenic impacts on various components of aquatic ecosystems. While great precautions are usually taken when selecting and calculating relevant core metrics, little attention is generally paid to the generation of the multimetric indicator, i.e. the combination of the different core metrics. Indeed, most multimetric indicators are generated by simply averaging or summing metrics, without taking into account their sensitivity and their variability. Moreover, few indicators provide a rigorous estimate of the uncertainty of the assessments, while this estimation is essential for managers. In this context, we developed a Bayesian framework to build multimetric indicators aiming at improving those two weaknesses. This framework is based on two phases. First, pressure-impact statistical models are developed to quantify the impact of pressure on various fish metrics. Then the Bayesian theorem is applied to estimate probabilities of being at a certain anthropogenic pressure level from fish observation and pressure-impact models outputs. The Bayesian theorem allows to combine objectively the different core metrics, taking into account their sensitivity and their variability, and to provide rigorous uncertainty quantification, which is especially valuable in the WFD context. The method is applied as illustrative example on transitional French water bodies to demonstrate its relevance, especially in the Water Framework Directive context though the method is generic enough to be applied in various contexts

L'amenagement forestier au Gabon: historique, bilan, perpectives

There is growing awareness of the need to sustainably manage forests in Central Africa. This paper reviews the current state in Gabon within the national context. Forests play a very important role in Gabon in view of their extensive area as well as their contribution to the national economy. There are three main forest regions: coastal sedimentary basin, North-East, and Central Gabon. Forest utilisation is largely controlled by foreign capital and includes few tree species, mainly Okoumé (75% in 1997), with comparatively low volumes extracted per hectare. Export of Okoumé and Ozigo was until recently a monopoly of SNBG, a state company now experiencing a deep crisis. The timber market is affected by the Asian crisis repercussions. Since the 50s the government, as owner, has tried to sustainably manage the forests. Pilot management schemes were undertaken and all forest concessions are required by law to have management plans. The main problem for the government is its capacity to enforce forest management, and for the concession holders the profitability of their investments. There are internal incentives (better forecast of harvest, rationalisation of forest road network, guarantee of access to managed forests), as well as international incentives, such as pressure for ecocertification and assistance to forest management. At national level the forest law reform will make sustainable management compulsory. Such constraints and incentives are not fully identified, however there is clearly increasing involvement of logging companies: feasibility studies on management of timber concessions, forest management agreements between government and concession holders. The cost of sustainable forest management appears globally acceptable. The success of a forest management policy in Gabon will depend on the capacity of the government to incorporate management as a natural component of forest utilisation, and control implementation

Un réseau de zones pilotes pour tester et améliorer les indicateurs de gestion durable des forêts au niveau régional sur la façade atlantique de l'Europe

Rapport FORSEE, Région Aquitaine - Critère VI : « Maintien d'autres bénéfices et conditions socio-économiques » - Indicateur : Emploi, CRPF Aquitaine, 35 p

Forêt / Bois / Papier, les emplois de la région Aquitaine

INSEE Aquitaine, n° 160, novembre, 4 p

Conséquences de la plasticité phénotypique et l'adaptation locale chez l'anguille européenne : évaluer les réponses de la population aux pressions anthropiques

International audienceAs a result of a collapse observed since the 80's, the European eel (Anguilla anguilla) is now classified as critically endangered in the IUCN Red List and the European Commission enforced a European Regulation which requires a reduction in all sources of anthropogenic mortality. The strong spatial heterogeneity of anthropogenic pressures affecting eel population in Europe combined with a spatial variability in life history traits at both the distribution area and river catchment scales raise specific challenges for management. This catadromous species represents a panmictic population that spawns in the Sargasso Sea and whose larvae are passively transported by ocean currents to the inner waters of Morocco to Norway. These features promote the emergence of phenotypic plasticity rather than local genetic adaptation as an adaptive response to spatially structured environment and suggest that life history traits heterogeneity may be a result of this adaptation. The first version of the evolutionary ecology-based model for eel (EvEel) explores spatial variability in terms of life history traits, tactics and demographic attributes as a result of adaptive phenotypic plasticity. Assuming fitness maximization, the model was able to reproduce most patterns observed across river catchment scale and distribution area. This suggests that sex determination, length-at-silvering and habitat use may be plastic mechanisms that allow eels to cope with environment variability. A second version of the model is currently being developed to take into account genetic variability in addition to phenotypic plasticity. A preliminary exploration of the model is exploring if the combination of both aspects improves the performance of the model and its ability to mimic observed patterns. Then, the model will be used to assess the impacts of anthropogenic pressures (habitat fragmentation, pollution or fishing) in terms of fertile biomass and population’s demographic attributes. After this theoretical step, model calibration and validation will be applied to a real case of study, such as the Garonne-Dordogne catchment. Finally, this model could serve as a decision-support tool to aid the management of the uncertain environment

Modèle génétique et d'écologie évolutive chez l'anguille européenne : GenEveel

International audienceEuropean eel: features and distribution, building the optimality model GenEvEel 1.0, first results

La plasticité phénotypique adaptative et la sélection spatialement variable chez l'anguille européenne modifient-elles l'effet des pressions anthropiques sur la population ?

National audienceLa population d’anguille européenne (Anguilla anguilla) est en déclin depuis les années 80, à tel point qu’elle est classée aujourd’hui en danger critique d’extinction dans la liste rouge de l’UICN. Les caractéristiques du cycle biologique de cette espèce la rendent particulièrement sensible à une grande variété de menaces et les mesures de conservation représentent un défi majeur. La reproduction de cette espèce catadrome et panmictique a lieu en mer des Sargasses, et est ensuite suivie d’un transport passif des larves par les courants océaniques jusqu’aux eaux continentales du Maroc à la Norvège. Ces particularités favorisent l’émergence d’une plasticité phénotypique plutôt qu'une adaptation génétique locale comme réponse adaptative à un environnement hétérogène et spatialement structuré. Le modèle EvEel (evolutionary ecology-based model for eel), visait à explorer si la variabilité spatiale en termes de traits d'histoire de vie, d'attributs démographiques et de tactique de vie, pouvait être le résultat d'une plasticité phénotypique adaptative. Basé sur des hypothèses de maximisation de fitness, le modèle est capable de reproduire la plupart des patrons observés à l'échelle du bassin-versant et à l'échelle de l'aire de répartition. Cela suggère que le déterminisme du sexe, la taille à maturation et le choix de l'habitat de croissance seraient autant de mécanismes plastiques permettant à l’anguille de faire face à un environnement changeant. Le but de ce travail de doctorat est de poursuivre le développement d’EvEel en ajoutant une composante génétique à la composante plasticité adaptative, et d’en analyser les conséquences sur la dynamique de la population. Une première exploration du modèle permettra de vérifier si dès la prise en compte des mécanismes de sélection locale qui seront ajoutés permettent de mieux reproduire les patrons spatiaux que ne le faisait la première version du modèle. Ensuite, l’impact des pressions anthropiques (rupture de connectivité, mortalité par pêche ou par pollution) sera intégré au niveau des processus de colonisation et de mortalité afin d'en quantifier les conséquences en termes de biomasse féconde et d'attributs démographiques dans la population. Après cette phase théorique, une étape de calibration/ validation sur données réelles sera tentée pour le cas de la Garonne-Dordogne. À terme, ce modèle pourra servir d’outil d’aide à la décision pour tester différents scénarios de gestion