Les récifs coralliens de la Réunion en 2007 : état des lieux et réseau de suivi

Abstract

Coral reefs of Réunion Island in 2007 : status report and monitoring network.— Réunion Island is 2500 km2 and belongs to the outermost regions of European Union (EU). The population attained 774 600 inhabitants in 2004 with 25 % living in the western part of the island, 80 % in the littoral zone (called «bas»). The gross domestic product (GDP) per capita is less than 50 % of the mean index of the EU. The rate of unemployment was of 33 % in 2004. Coral reef ecosystems extend over 12 km2 along 25 km of the west and south coasts of the island. In addition to the natural infl uence of climatic events (global change) coral reef ecosystems are impacted by direct and indirect influences of the increase of human population. Direct impacts are mainly due to human overfrequenting of reef flats and overfishing. Indirect impacts are due to urbanization and to industrial, agricultural and urban pollutions. The competence in marine environment is assumed by an administration (Direction Régionale de l’Environnement). Researches on coral reefs are run by research institutes and NGO. The first coral reef monitoring network was set up in 1998 on the Saint-Gilles/La Saline reef. Since then, it was extended to the three other main reef units (Saint-Leu, Étang-Salé, Saint-Pierre) and the data are gathered since 2001 by ecoguards of the association «Parc Marin de la Réunion», with the partnership of the university (Laboratoire d’Ecologie Marine). Data are stored in a database (COREMO) and analysed by ARVAM (Agence pour la Recherche et la Valorisation Marine). The operation is funded both by the state administration and a local administration (Conseil Régional). Réunion Island is a part of the South-West Indian Ocean node of the Global Coral Reef Monitoring Network (GCRMN). It is regularly involved in the writing of the «Status of coral reefs of the world». At the same time another network involving stakeholders is built using the Reef Chek protocole. At the present time, coral reefs of Réunion Island are deteriorated. If the density of the targeted species of fi sh has not changed since 1999, the surface of live corals has shown a significant decrease on half of the 14 stations, particularly after two bleaching events in 2003 and 2004. The various negative impacts due to human activities contribute to weaken these ecosystems and to decrease their resilience. Hence, they are less and less able to resist exceptional climatic events (hurricanes, swells) and the bad impacts of global change (bleaching). To face to the stake of long term development, 75 % of the reef units of the island are protected since February 2007 by the status of «Réserve Naturelle Nationale Marine» (35 km2 of marine protected area).