Systèmes de croyance Niomankas et gestion des ressources naturelles de mangroves

peer reviewedLe concept de «savoirs endogènes» constitue actuellement l’un des axes majeurs de la réflexion autour de la problématique de la conservation de la biodiversité. En effet, on se rend de plus en plus compte que l’activité de conservation de la diversité biologique, qui met à contribution les organisations locales, les structures étatiques et les ONG environnementales, ne peut pas seulement s’appuyer sur les connaissances scientifiques. La réflexion autour des savoirs écologiques locaux (Technical Ecological Knowledge [TEK]), et leur valorisation, apparaît comme une solution pour une gestion durable et viable des écosystèmes marins et côtiers, en particulier pour les forêts de mangrove du Siné-Saloum. Au Sénégal, l’ensemble du littoral subit depuis plusieurs décennies les effets de la désertification. Les initiatives se multiplient dans la Réserve de la Biosphère du Delta du Saloum [1]*** (RBDS) pour réhabiliter les écosystèmes côtiers. Il serait intéressant de voir quels peuvent être les apports des savoirs locaux, ceux des Niominka et Socé, dans la dynamique globale de conservation de la biodiversité écologique. Au moment où des plans de gestion de la mangrove [2] sont en train d’être conçus, il serait bon d’intégrer les savoirs écologiques endogènes dans le processus de leur conception et de mise en œuvre. En effet, dans le jeu des interactions entre communautés locales et ONG, donc intervenants extérieurs, il peut arriver que des réactions de rejet se manifestent. S’il en est ainsi, c’est parce que les ONG sont parfois porteuses d’initiatives qui ne tiennent pas compte des manières de penser, des rapports qui lient la nature aux populations autochtones, des systèmes de conception, de représentation et d’occupation de l’espace ou d’appropriation des ressources. Chez les Niominkas du Siné-Saloum, il existe des croyances et perceptions qui ont eu un impact positif sur la protection de l’environnement. Selon l’anthropologue sénégalais Massaer Diallo [3], «si ce que l’on appelle aujourd’hui “le respect de l’environnement” et la “gestion durable des ressources naturelles” a des cas équivalents dans des cultures et sociétés dites traditionnelles (régies par des logiques endogènes et anciennes), c’est parce que ces dernières étaient fondées sur une conception, des règles et valeurs qui impliquaient voire édictaient un rapport harmonieux ou équilibré avec la nature (physique, animale et végétale)». En voici quelques illustrations. La sacralisation de Jiffa, Péthiamak, chez les Sérères de Djilor, fait que ces sites — même si ce n’était pas l’objectif recherché — sont aujourd’hui les moins agressés dans la communauté rurale [4]. L’injonction du génie protecteur du Loog, Laga ndong, de ne parler que le sérère dans la zone de pêche Niamokine — dans un pays où l’écrasante majorité parle wolof — a favorisé le contrôle du bolong par les Niominkas et la limitation de l’exploitation de ses ressources aux autochtones. De plus, l’islamisation des sociétés traditionnelles sérères a introduit un rapport de type nouveau entre l’homme et la nature parce que le fait de couper un arbre ou tout simplement des feuilles d’arbres sans en avoir besoin est associé à un péché. Celui qui abuse de la ressource végétale est selon le Coran un pécheur. En planter, c’est attirer la miséricorde divine sur soi, dit-on dans le texte sacré des musulmans. Ces représentations religieuses ont donc des incidences sur l’équilibre de la nature. Les savoirs écologiques locaux présentent un intérêt bien particulier mais il faut se garder de faire de l’ethnologisme. Et puis, il y a chez les Niominka une forte croyance selon laquelle la mangrove est un don de Dieu. Par conséquent, la pérennité des ressources qu’elle génère est garantie par une divinité. Quelle est la place de ces croyances dans le processus de désintégration des forêts de mangrove dans le Siné et le Saloum? Le présent article tente de fournir des éléments d’appréciation sur la place des savoirs locaux dans la conservation de la diversité biologique chez les communautés Niominka de la RBDS

The inner radio jet region and the complex environment of SS433

We present multi-frequency VLBA+VLA observations of SS433 at 1.6, 5 and 15 GHz. These observations provide the highest angular resolution radio spectral index maps ever made for this object. Motion of the components of SS433 during the observation is detected. In addition to the usual VLBI jet structure, we detect two radio components in the system at an anomalous position angle. These newly discovered radio emitting regions might be related to a wind-like equatorial outflow or to an extension of the accretion disk. We show that the radio core component is bifurcated with a clear gap between the eastern and western wings of emission. Modelfitting of the precessing jets and the moving knots of SS433 shows that the kinematic centre -- i.e. the binary -- is in the gap between the western and eastern radio core components. Spectral properties and observed core position shifts suggest that we see a combined effect of synchrotron self-absorption and external free-free absorption in the innermost AU-scale region of the source. The spatial distribution of the ionized matter is probably not spherically symmetric around the binary, but could be disk-like.Comment: Accepted for publication by Astronomy and Astrophysic

Object identification and characterization with hyperspectral imagery to identify structure and function of Natura 2000 habitats

Habitat monitoring of designated areas under the EU Habitats Directive requires every 6 years information on area, range, structure and function for the protected (Annex I) habitat types. First results from studies on heathland areas in Belgium and the Netherlands show that hyperspectral imagery can be an important source of information to assist the evaluation of the habitat conservation status. Hyperspectral imagery can provide continuous maps of habitat quality indicators (e.g., life forms or structure types, management activities, grass, shrub and tree encroachment) at the pixel level. At the same time, terrain managers, nature conservation agencies and national authorities responsible for the reporting to the EU are not directly interested in pixels, but rather in information at the level of vegetation patches, groups of patches or the protected site as a whole. Such local level information is needed for management purposes, e.g., exact location of patches of habitat types and the sizes and quality of these patches within a protected site. Site complexity determines not only the classification success of remote sensing imagery, but influences also the results of aggregation of information from the pixel to the site level. For all these reasons, it is important to identify and characterize the vegetation patches. This paper focuses on the use of segmentation techniques to identify relevant vegetation patches in combination with spectral mixture analysis of hyperspectral imagery from the Airborne Hyperspectral Scanner (AHS). Comparison with traditional vegetation maps shows that the habitat or vegetation patches can be identified by segmentation of hyperspectral imagery. This paper shows that spectral mixture analysis in combination with segmentation techniques on hyperspectral imagery can provide useful information on processes such as grass encroachment that determine the conservation status of Natura 2000 heathland areas to a large extent. A limitation is that both advanced remote sensing approaches and traditional field based vegetation surveys seem to cause over and underestimations of grass encroachment for specific categories, but the first provides a better basis for monitoring if specific species are not directly considered

Multilevel reflectance switching of ultrathin phase-change films

Several design techniques for engineering the visible optical and near-infrared response of a thin film are explored. These designs require optically active and absorbing materials and should be easily grown on a large scale. Switchable chalcogenide phase-change material heterostructures with three active layers are grown here using pulsed laser deposition. Both Fabry-Perot and strong interference principles are explored to tune the reflectance. Robust multilevel switching is demonstrated for both principles using dynamic ellipsometry, and measured reflectance profiles agree well with simulations. We find, however, that switching the bottom layer of a three-layer device does not yield a significant change in reflectance, indicating a maximum in accessible levels. The pulsed laser deposition films grown show promise for optical display applications, with three shown reflectance levels. Published under license by AIP Publishing.</p

A human colonic crypt culture system to study regulation of stem cell-driven tissue renewal and physiological function

The intestinal epithelium is one of the most rapidly renewing tissues in the human body and fulfils vital physiological roles such as barrier function and transport of nutrients and fluid. Investigation of gut epithelial physiology in health and disease has been hampered by the lack of ex vivo models of the native human intestinal epithelium. Recently, remarkable progress has been made in defining intestinal stem cells and in generating intestinal organoid cultures. In parallel, we have developed a 3D culture system of the native human colonic epithelium that recapitulates the topological hierarchy of stem cell-driven tissue renewal and permits the physiological study of native polarized epithelial cells. Here we describe methods to establish 3D cultures of intact human colonic crypts and conduct real-time imaging of intestinal tissue renewal, cellular signalling, and physiological function, in conjunction with manipulation of gene expression by lentiviral or adenoviral transduction. Visualization of mRNA- and protein-expression patterns in cultured human colonic crypts, and cross-validation with crypts derived from fixed mucosal biopsies, is also described. Alongside studies using intestinal organoids, the near-native human colonic crypt culture model will help to bridge the gap that exists between investigation of colon cancer cell lines and/or animal (tissue) studies, and progression to clinical trials. To this end, the near native human colonic crypt model provides a platform to aid the development of novel strategies for the prevention of inflammatory bowel disease and cancer

A Massive Jet Ejection Event from the Microquasar SS 433 Accompanying Rapid X-Ray Variability

Microquasars occasionally exhibit massive jet ejections which are distinct from the continuous or quasi-continuous weak jet ejections. Because those massive jet ejections are rare and short events, they have hardly been observed in X-ray so far. In this paper, the first X-ray observation of a massive jet ejection from the microquasar SS 433 with the Rossi X-ray Timing Explorer (RXTE) is reported. SS 433 undergoing a massive ejection event shows a variety of new phenomena including a QPO-like feature near 0.1 Hz, rapid time variability, and shot-like activities. The shot-like activity may be caused by the formation of a small plasma bullet. A massive jet may be consist of thousands of those plasma bullets ejected from the binary system. The size, mass, internal energy, and kinetic energy of the bullets and the massive jet are estimated.Comment: 21 pages including 5 figures, submitted to Ap

The properties of the gamma-ray blazars in the CJ-F VLBI sample

We present first results from the analysis of multi-epoch VLBI observations of the EGRET detected sources [9] in the CJ-F sample (Caltech Jodrell-Flat-spectrum, [10]). These objects form a subsample of 14 sources within the 293 AGN of the full CJ-F sample. 5 GHz VLBI snapshot observations of the CJ-F sources are continuously being performed in order to create a valid database for thorough statistical tests of pc-scale jet motion in AGN. All gamma-bright CJ-F AGN have been observed at least twice with the VLBA, which enables us to investigate jet component motions and paths. In particular, we concentrate on the analysis of those properties supposed to be essential for gamma-ray production, i.e., superluminal motion and bending. A paper discussing the possible relation between morphological changes and gamma-ray flaring/production is in preparation

A Multi-Epoch VLBI Survey of the Kinematics of CJF Sources; Part I: Model-Fit Parameters and Maps

Context: This is the first of a series of papers presenting VLBI observations of the 293 Caltech-Jodrell Bank Flat-Spectrum (hereafter CJF) sources and their analysis. Aims: One of the major goals of the CJF is to make a statistical study of the apparent velocities of the sources. Methods: We have conducted global VLBI and VLBA observations at 5 GHz since 1990, accumulating thirteen separate observing campaigns. Results: We present here an overview of the observations, give details of the data reduction and present the source parameters resulting from a model-fitting procedure. For every source at every observing epoch, an image is shown, built up by restoring the model-fitted components, convolved with the clean beam, into the residual image, which was made by Fourier transforming the visibility data after first subtracting the model-fitted components in the uv-plane. Overplotted we show symbols to represent the model components. Conclusions: We have produced VLBI images of all but 5 of the 293 sources in the complete CJF sample at several epochs and investigated the kinematics of 266 AGN.Comment: Figure 1 and Table 2 are only available in electronic form at the CDS and soon at http://www.mpifr-bonn.mpg.de/staff/sbritzen/cjf.htm

Images of an equatorial outflow in SS433

We have imaged the X-ray binary SS433 with unprecedented Fourier-plane coverage at 6cm using simultaneously the VLBA, MERLIN, and the VLA, and also at 20cm with the VLBA. At both wavelengths we have securely detected smooth, low-surface brightness emission having the appearance of a `ruff' or collar attached perpendicularly to the well-studied knotty jets in this system, extending over at least a few hundred AU. We interpret this smooth emission as a wind-like outflow from the binary, and discuss its implications for the present evolutionary stage of this system.Comment: Accepted by ApJ Letter