Portail "HAL-Francophonie Afrique et Océan Indien"
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Les risques naturels à Mayotte dans le contexte du réchauffement climatique.
No full textPrésentation dans le cadre du COMEX « Gestion de crise et risque naturel » de l’association Mlézi Maore, Cavani, Mayotte
Dialogue entre science et société civile au REVOSIMA : le groupe de travail « Médiation scientifique »
No full textNational audienc
La mémoire du risque cyclonique à Mayotte : de la mémoire habitante à la mémoire paysagère, le cas de Kamisy (1984) et Feliksa (1985)
No full textInternational audienceDans cette communication nous reviendrons sur le concept de mémoire du risque que nous développerons au prisme d’une recherche menée auprès des habitants de Mayotte et de l’exploitation de la documentation archivistique. Nous proposerons une discussion sur le concept de mémoire du risque et de son élargissement à des objets autre que les éléments transmis par le témoignage ou les archives en questionnant la place des paysages comme objet produit par les sociétés et porteur en lui-même d’une mémoire à valoriser dans le cadre de stratégie de prévention des risques
High-resolution species distribution modelling of two coastal biogenic habitat-forming species in an Ecologically and Biologically Significant Area of the Bay of Fundy, Canada
No full textInternational audienceHigh-resolution species distribution models (SDMs) were developed for two benthic invertebrate species of marine conservation significance across a 113 km2 Ecologically and Biologically Significant Area (EBSA) of the Bay of Fundy, Canada. The stalked tunicate, Boltenia ovifera, and horse mussel, Modiolus modiolus, can form coastal biogenic habitat and are vulnerable to disturbance. A near-seabed imaging survey (depths ranging from 8 to 79 m) provided presence, absence, and abundance data for both species. Boosted Regression Tree SDMs combined these data with 11 environmental variables. Presence-probability distributions were generated; however, abundance patterns could not be adequately modelled. Oblique geographic coordinates, which incorporate location of samples as information, proved useful for predicting species presence, along with seabed rugosity, maximum current speed and bathymetry for B. ovifera, and maximum and minimum current speed along with seabed rugosity for M. modiolus. High-resolution SDMs (in this case, 5-m grid) provide enhanced spatial context for ocean managers towards marine spatial planning in high-use coastal marine environments where bottom contact fisheries access and other coastal development must be balanced against marine conservation objectives
« Sprachraumpionier / als Jäger im Weltall ». Métamorphoses de l’espace dans les collages de Lydia Daher
No full textInternational audienceMIT JEDEM WORTerobern wir nichts. Und doch heißts mutig sein:dem Mantel der Weltein Stück StoffENT REISSEN.Publié dans le recueil Insgesamt so, diese Welt (2012), ce poème de Lydia Daher annonçait déjà le geste créateur de sa publication suivante. Avec Und auch nun, gegenüber dem Ganzen – dies (2014), la poétesse explore la surface du monde et ses déchirures, au sens propre : un monde de papier, celui des journaux dont, durant un an, elle a découpé et déchiré les pages culturelles pour en réagencer à sa guise les mots et les images. Chacune des 101 créations qui en résultent est issue du contenu restreint d’une critique littéraire devenue le point de départ d’un univers nouveau, où se côtoient et s’entrechoquent différents niveaux de réalité. D’ailleurs, quel est cet espace vers lequel pointent les déictiques « diese Welt », « dies » ? Désignent-ils le monde "réel" dont traitent les articles de presse, les territoires imaginaires nés de leur réagencement, la spatialité du collage sur la page, la matérialité du langage ou celle du papier journal déchiré ? Lydia Daher ne se contente pas de lire les territoires comme on lit le journal : elle les interroge, les réécrit, les met en mouvement ou les recompose en faisant apparaître leurs failles et leurs fragilités.La communication proposée a étudié la manière dont ces collages prélèvent et documentent l’espace tout autant qu’ils le fictionnalisent. Une attention particulière a été portée au motif de la déchirure, qui fait se côtoyer plusieurs niveaux de réalité tout en affichant sa propre matérialité – désignant ainsi l’ensemble de la création comme factice. Mais loin d’être de simples jeux de surface, les re-créations spatiales de Lydia Daher ont une dimension véritablement politique. Empreintes d’une rébellion sourde, elles prennent position sur un monde de l’information aussi fragile et fragmenté que les collages eux-mêmes. Sous cette colère latente, les déchirures du papier journal laissent entrevoir l’esquisse d’un contre-espace, une utopie cachée dans les interstices entre texte et image, derrière les fêlures du monde tel qu’il va : « Das Unmögliche buchstabiert die Welt neu », nous promet l’un des poèmes
Complex genetic determinism of male-fertility restoration in the gynodioecious snail Physa acuta
No full textInternational audienceMale fertility in plants is often controlled by the interaction between mitochondrial and nuclear genes. Some mitotypes confer cytoplasmic male sterility (CMS), making the individual male-sterile, unless the nuclear background contains alleles called restorers, which suppress the effects of CMS and restore the hermaphroditic phenotype. Restorers in cultivated crops are often alleles with strong and dominant effect, but in wild plants, data often suggest more complex systems. Here, we characterized the inheritance and specificity of restoration in a new CMS model, the freshwater snail Physa acuta. We explored two different populations: (i) a naive population, i.e., without contact with CMS in the past 80 generations, and (ii) a non-naive population, where CMS is present and largely restored. Although we found male fertility of individuals with CMS mitogenomes to be heritable in both contexts, this genetic determinism was of a different nature depending on population history. In naive populations not coevolved with CMS, the background variation may include alleles that happen to act as weak quantitative modifiers of the penetrance of CMS, while in populations coevolved with CMS, selection may have favoured, when such variants were available, the emergence of strong alleles with a dominant effect
The Use of New Biologically Based Technological Development in the Management of Crown-of-Thorns Sea Stars
No full textInternational audienceCrown-of-thorns sea star (CoTS) outbreaks represent one of the biggest threats to scleractinian coral reefs across the Indo-Pacific, and this threat is further exacerbated by ocean warming, cyclones and ocean acidification. There is currently a large collective effort by stakeholders across Indo-Pacific nations to develop technologies to accurately manage (predict, monitor and reduce) these outbreaks. Emerging technologies include: low-cost and high-throughput eDNA profiling of seawater (biosensors) to accurately count the abundance of CoTS in a local area; developing chemosensory attractants and dispersants to herd CoTS for efficient removal; desynchronising CoTS reproduction by altering the timing of CoTS reproductive cues; producing CoTS with lower fecundity through gene editing/contraceptives; using machine learning technologies and robots to automatically detect and cull CoTS; making CoTS more susceptible to diseases through microbiome manipulation to reduce population sizes; strategically planting corals more resilient to CoTS predation, e.g., more venomous corals; and facilitating the predation of CoTS by increasing the numbers of CoTS predators through marine protected area (MPA) designation and habitat restoration. In this chapter, we discuss the emerging technologies and considerations that should be taken into account to effectively manage CoTS outbreaks for future reef resilience
Involvement of the Soil Seed Bank in the Natural Regeneration of Forest Ecosystems in the Northern Sector of the Léfini Reserve (Republic of Congo)
No full textInternational audienceThe study on the involvement of the soil seed bank in the natural regeneration of forests was carried out in the northern sector of the Léfini reserve. The aim was to assess the resilience of these woody formations. Data were collected in 8 isolated plots of 1 ha, in which woody trees of dbh ≥ 10 cm were inventoried and counted, and soil samples were taken at 5 points. At a rate of 40 samples per level, the horizons involved were: 0–5 and 5–10 cm. The floristic inventory reveals 2903 trees for 113 species, 38 families and 92 genera. The main taxa were Tetraberlinia bifoliolata, Petersianthus macrocarpus, Duvigneaudia inopinata, Pentaclethra eetveldeana and Diospyros dendo . Germination tests on soil samples revealed 1763 individuals belonging to 50 species in 32 families. The dominant species were Pollia condensata, Musanga cecropioides, Trema orientalis and Harungana madagascariensis . The specific composition of the soil seed bank reveals low diversity and heterogeneity associated with forest facies and soil horizons, as underpinned by biodiversity indices. Although the soil seed bank is dominated by native herbaceous plants and pioneer woody plants, mature forest species are almost exclusively confined to the first horizon. Renewal of the flora depends mainly on animals and, to a lesser extent, on anemochory. The standing flora is not very similar to that of the soil seed bank. The low degree of similarity between the floristic composition and the soil seed bank, which is dominated by pioneer taxa, suggests that the front may be characterised by disturbance. In order to ensure the long‐term survival of the forests that are essential to people’s well‐being, assisted natural regeneration is recommended, particularly for the most prized taxa
Dynamics of Infragravity Waves Across the Southern Reef Barrier of Mayotte, Indian Ocean
No full textInternational audienceDue to climate change, tropical islands are being increasingly exposed to coastal hazards. Under energetic incident swells, infragravity (IG) waves can have a key contribution to extreme water levels and flooding, but their dynamics at barrier reef remains little studied. In this context, this study analyses IG wave generation mechanisms and transformations across a barrier reef to the southwest of Mayotte (Indian Ocean), combining a new comprehensive field dataset with phase resolving wave modelling. This analysis reveals that IG waves are mostly breakpoint-forced and suffer a substantial dissipation by bottom friction, particularly at low tide. Numerical experiments with reduced bottom friction representing a degraded coral reef suggest that IG waves would grow by about 20% across the reef at high tide. This study highlights the key role of coral reefs to dissipate IG waves and hence limit extreme water levels and subsequent coastal hazards.</div