Étude des impacts écologiques du dynamisme spatio-temporel des habitats naturels sur la faune menacée du Complexe Zones Humides Mahavavy-Kinkony, Madagascar

This study of the Mahavavy-Kinkony Wetland Complex (MKWC) assesses the impacts of habitat change on the resident globally threatened fauna. Located in Boeny Region, northwest Madagascar, the Complex encompasses a range of habitats including freshwater lakes, rivers, marshes, mangrove forests, and deciduous forest. Spatial modelling and analysis tools were used to (i) identify the important habitats for selected, threatened fauna, (ii) assess their change from 1950 to 2005, (iii) detect the causes of change, (iv) simulate changes to 2050 and (v) evaluate the impacts of change. The approach for prioritising potential habitats for threatened species used ecological science techniques assisted by the decision support software Marxan. Nineteen species were analysed: nine birds, three primates, three fish, three bats and one reptile. Based on knowledge of local land use, supervised classification of Landsat images from 2005 was used to classify the land use of the Complex. Simulations of land use change to 2050 were carried out based on the Land Change Modeler module in Idrisi Andes with the neural network algorithm. Changes in land use at site level have occurred over time but they are not significant. However, reductions in the extent of reed marshes at Lake Kinkony and forests at Tsiombikibo and Marofandroboka directly threaten the species that depend on these habitats. Long term change monitoring is recommended for the Mahavavy Delta, in order to evaluate the predictions through time. The future change of Andohaomby forest is of great concern and conservation actions are recommended as a high priority. Abnormal physicochemical properties were detected in lake Kinkony due to erosion of the four watersheds to the south, therefore an anti-erosion management plan is required for these watersheds. Among the species of global conservation concern, Sakalava rail ( Amaurornis olivieri ), Crowned sifaka ( Propithecus coronatus ) and dambabe ( Paretroplus dambabe ) are estimated the most affected, but at the site level Decken’s sifaka ( Propithecus deckeni ) , kotsovato ( Paretroplus kieneri ) and Madagascan big-headed turtle ( Erymnochelys madagascariensis ) are also threatened. Local enforcement of national legislation on hunting means that MKWC is among the sites where the flying fox ( Pteropus rufus ) and Madagascan rousette ( Rousettus madagascariensis ) are well protected. Ecological restoration, ecological research and actions to reduce anthropogenic pressures are recommended. RESUME Cette recherche menee dans le Complexe Zones Humides Mahavavy-Kinkony a pour but d’evaluer les impacts ecologiques du changement des habitats naturels sur les especes menacees de sa faune. Des outils tels que le SIG, la teledetection ainsi que Marxan ont ete combines avec les etudes bibliographiques et les travaux de terrains pour (i) identifier les habitats naturels prioritaires pour la faune menacee du site, (ii) evaluer leur changement entre 1950 et 2005, (iii) deceler les causes du changement, (iv) elaborer une prospective des changements en 2050 et (v) evaluer les impacts du changement. Le changement des habitats naturels s’est deroule au cours des temps mais il n’a pas ete assez important au niveau global du site pour transformer radicalement les occupations du sol. Toutefois, le recul des phragmitaies du lac Kinkony et des forets de Tsiombikibo et de Marofandroboka menace les especes qui en dependent. Le suivi du delta de Mahavavy doit etre poursuivi et intensifie pour evaluer les menaces qui pesent sur lui dans le contexte des changements climatiques. La situation de la foret d’Andohaomby est preoccupante et son avenir menace en l’absence d’actions concretes. L’analyse de vulnerabilite a l’erosion du bassin du Kinkony a demontre que les changements physico-chimiques dus a l’erosion dans les quatre bassins au Sud du lac rendent necessaires des amenagements anti-erosifs. Parmi les especes de la faune vertebree, Amaurornis olivieri , Propithecus coronatus et Paretroplus dambabe sont les especes les plus affectees globalement, mais au niveau du site Propithecus deckeni , Paretroplus kieneri et Erymnochelys madagascariensis sont tout aussi vulnerables. Pteropus rufus et Rousettus madagascariensis seraient les especes les mieux protegees.