13 research outputs found
How does climate change Impact island rainforests: first measurements in The Lesser Antilles archipelago
International audienceRainforests in tropical islands are characterized by high endemism and unusual structures. Canopies are lower than in continental areas with a similar climate, but the number of trees per hectare is much higher. It is likely that these structural attributes are due to the frequency of hurricanes but also more generally to some peculiarities of island climates.Recent works show that in areas where plants are subject to seasonal drought, the metabolism of tropical trees negatively responds to rising temperatures and rainfall reduction. Given the particularities of island ecosystems, we wanted to study the behavior of forests growing in climates without true dry season.The results obtained on four 1-hectare plots (4312 trees) show that during the last nine years, tree growth has accelerated and at the same time, tree mortality has increased - although the estimation of mortality is more uncertain. These joint trends reflect a significant acceleration in the turnover of tree stands.The measurements carried out thanks to the "Forest Ecosystems Observatory" put in place since 2010, demonstrate that the Caribbean island rainforests are impacted by the current climate change and that they respond in a singular way. The results obtained do not provide information on changes in biodiversity or loss of endemic species, but they suggest that Lesser-Antilles rainforests are reducing their carbon storage capacity
Typologie des ripisylves des riviÚres de Guadeloupe, un premier pas vers le développement de techniques de génie végétal avec des espÚces locales
National audienceThe PROTĂGER project aims to promote soil bioengineering techniques to preserve the extreme biodiversity of Guadeloupe's riparian environments, while protecting the population and their property from the risks incurred during river floods and cyclonic events. The first phase of the project consisted in describing the archipelago's riparian zones, in order to know their natural patterns and to be able to draw inspiration from them to develop nature-based solutions. Out of the 270 banks sampled, 302 species, 231 of which were native, were encountered, representing 10% of the local flora, reflecting the highly forested nature of the archipelago and its exceptional diversity. The analysis of these surveys allowed us to define 12 types of riparian vegetation, and to document 80 species that could potentially be used in soil bioengineering. The study presents 30 of them in the form of individual sheets available on the project website with their description, phenology, protection status, ecology, use and conditions of implementation. Beyond the typology and the specific sheets, this work also showed the alarming state of the Guadeloupeâs riparian forests, in particular on the downstream part of the rivers, with habitats degraded by pollution and the presence of invasive alien species.Le projet PROTĂGER vise Ă promouvoir les techniques de gĂ©nie vĂ©gĂ©tal pour prĂ©server lâextrĂȘme biodiversitĂ© des milieux rivulaires de Guadeloupe, tout en protĂ©geant la population et leurs biens, des risques encourus lors des crues de riviĂšre et des Ă©vĂšnements cycloniques. La premiĂšre phase du projet a consistĂ© Ă dĂ©crire les ripisylves de lâarchipel, afin dâen connaitre les modĂšles naturels et de pouvoir sâen inspirer pour dĂ©velopper des solutions fondĂ©es sur la nature. Sur les 270 berges Ă©chantillonnĂ©es, 302 espĂšces dont 231 indigĂšnes ont Ă©tĂ© rencontrĂ©es, soit 10 % de la flore locale, reflĂ©tant la nature trĂšs forestiĂšre de lâarchipel et son exceptionnelle diversitĂ©. Lâanalyse de ces relevĂ©s a permis de dĂ©finir 12 types de ripisylves, et de documenter 80 espĂšces potentiellement utilisables en gĂ©nie vĂ©gĂ©tal. LâĂ©tude prĂ©sente 30 d'entre elles sous forme de fiches individuelles disponibles sur le site internet du projet avec leur description, leur phĂ©nologie, leur statut de protection, leur Ă©cologie, leur usage et leur condition dâutilisation. Au-delĂ de la typologie et des fiches spĂ©cifiques, ce travail a aussi montrĂ© lâĂ©tat alarmant des ripisylves de Guadeloupe, notamment sur la partie aval des cours dâeau, avec des habitats dĂ©gradĂ©s par la pollution et la prĂ©sence dâespĂšces exotiques envahissantes
Lâinformation Ă©conomique, XVIe-XIXe siĂšcle
CoĂ»teuse, inĂ©galement partagĂ©e, lâinformation est une arme dĂ©cisive face Ă lâincertitude. Les travaux Ă©conomiques rĂ©cents, sâĂ©loignant de lâorthodoxie nĂ©o-classique, ont mis en valeur le rĂŽle central de lâinformation dans le fonctionnement des marchĂ©s. De fait, du XVIe au XIXe siĂšcle, quand sâintensifient les circulations et les relations commerciales, les diffĂ©rents acteurs marquent leur appĂ©tit dâinformation, et agissent ensuite en fonction de ce quâils croient savoir. Ainsi, lâinformation recueillie sur lâĂ©conomie joue elle-mĂȘme un rĂŽle dans lâĂ©conomie. Elle est donc un Ă©lĂ©ment intrinsĂšque du fonctionnement mĂȘme des marchĂ©s, une donnĂ©e des jeux de lâĂ©change. Les Ă©tudes rĂ©unies ici, Ă la suite de deux journĂ©es dâĂ©tudes rĂ©alisĂ©es en 2004 et 2006 et rassemblant les meilleurs spĂ©cialistes, nous emmĂšnent des correspondances marchandes et circulaires commerciales aux Affiches, Annonces et autres feuilles dâinformation. Mais elles soulignent aussi lâaction dâun autre acteur : depuis les initiatives de Colbert jusquâĂ lâessor de la Statistique gĂ©nĂ©rale de la France, lâĂtat sâest affirmĂ© comme un grand collecteur mais aussi producteur dâinformation Ă©conomique. De sorte que, aussi libĂ©rale que fĂ»t devenue sa politique, au XIXe siĂšcle, il a continuĂ© de jouer un rĂŽle crucial, quand lui seul pouvait rassembler des donnĂ©es dispersĂ©es. En avoir ou pas : depuis lâĂ©poque moderne, chacun Ă©tait conscient de lâenjeu que reprĂ©sentait lâinformation Ă©conomique. LĂ encore, le passĂ© Ă©claire notre prĂ©sent
CARIB-COAST caribbean network for coastal risks related with climate change
International audienc
Villes et districts industriels en Europe occidentale (XVIIe-XXe siĂšcle)
Au moment oĂč les pays occidentaux redĂ©couvrent les avantages de la production flexible et des communautĂ©s territoriales d'entreprises, ce livre s'interroge sur le rĂŽle de la ville dans le fonctionnement des systĂšmes productifs locaux. Il Ă©tudie la place de la ville et des municipalitĂ©s dans l'organisation du district industriel et l'effet, en retour, de la prĂ©sence du district sur le dĂ©veloppement de la ville. Il met en lumiĂšre le rĂŽle des valeurs et des institutions urbaines comme Ă©lĂ©ments constitutifs du district (coopĂ©ration entre firmes, consensus social et mobilitĂ©). Il analyse enfin les mĂ©canismes d'adaptation qui ont souvent permis aux districts de survivre aux mutations industrielles que l'Europe a connues depuis l'Ă©poque moderne
Pre-assessments of plant conservation status in islands: the case of French Overseas Territories
International audienceAssessment methods have been developed to estimate a preliminary conservation status for species and subsequently to facilitate the building of Red Lists. Such pre-assessment methods could be particularly useful in the French Overseas Territories (FOTs) where Red Lists tend to be outdated or absent and where a high number of endemic species face detrimental anthropogenic pressures. We first aimed to conduct a preliminary assessment (hereafter, pre-assessment) of the conservation status of endemic plants from Guadeloupe, Martinique, RĂ©union, Mayotte, French sub-Antarctic islands, New Caledonia, and Scattered Islands. We then compared the various methods used in conducting the pre-assessment and discussed ways to adapt these methods to small territories. We compiled occurrence data of endemic species identified thanks to a previous taxonomic work and pre-assessed their conservation status under Red List criteria A and B and the use of a Random Forest algorithm. We then measured the accuracy, specificity, and sensitivity of each method based on existing Red Lists. The Random Forest algorithm and a method based on range-size performed best at correctly attributing conservation status. Using these pre-assessment methods, we estimated that up to 60% of the endemic flora of the FOTs is potentially threatened. Range restriction but also anthropogenic pressures were key factors that explained these risks. Pre-assessment methods are useful tools to get a first measure of species conservation status. These methods should be adapted to the territories considered and their conservation issues in order to reach a good performance
Pre-assessments of plant conservation status in islands: the case of French Overseas Territories
International audienceAssessment methods have been developed to estimate a preliminary conservation status for species and subsequently to facilitate the building of Red Lists. Such pre-assessment methods could be particularly useful in the French Overseas Territories (FOTs) where Red Lists tend to be outdated or absent and where a high number of endemic species face detrimental anthropogenic pressures. We first aimed to conduct a preliminary assessment (hereafter, pre-assessment) of the conservation status of endemic plants from Guadeloupe, Martinique, RĂ©union, Mayotte, French sub-Antarctic islands, New Caledonia, and Scattered Islands. We then compared the various methods used in conducting the pre-assessment and discussed ways to adapt these methods to small territories. We compiled occurrence data of endemic species identified thanks to a previous taxonomic work and pre-assessed their conservation status under Red List criteria A and B and the use of a Random Forest algorithm. We then measured the accuracy, specificity, and sensitivity of each method based on existing Red Lists. The Random Forest algorithm and a method based on range-size performed best at correctly attributing conservation status. Using these pre-assessment methods, we estimated that up to 60% of the endemic flora of the FOTs is potentially threatened. Range restriction but also anthropogenic pressures were key factors that explained these risks. Pre-assessment methods are useful tools to get a first measure of species conservation status. These methods should be adapted to the territories considered and their conservation issues in order to reach a good performance