![]() ![]() If, to such urban pollution we add sugar industry and rum distillery effluent – rich in organic and mineral matter – thrown into the rivers without any prior treatment, all the elements converge for creating substantial necrosis of the table reefs. It is evident that the coastal fringe is highly urbanised, since 85% of the total population resides there. In Réunion Island, for example, despite considerable efforts over recent years for treating sewage water, untreated effluent is still being spilled daily into the lagoon, polluting the environment. 1.2.3 Large-scale urban and industrial pollutionĩ Urban and industrial activity also participate in damaging the reefs. The table reefs which face the mining slopes have undergone substantial damage (Saffache 2002 ). Hence, during heavy rains, this lateritic waste rock feeds sediment into the rivers, to later fossilise the seabed. Over the past centuries, New Caledonia, the world’s third nickel producer, a little over 300 million cubic meters of waste rock has been removed and piled in the open air, without any protection or stabilisation measures being planned. In New Caledonia, for example, although farming was never a dynamic sector (it represents but 1.5 to 1.9% of the GDP), vegetable crop surfaces occupy steep slopes which release large volumes of sediment during the rainy season, these are the particles which later accumulate in the lagoons.Ĩ Hyper sedimentation of the coastline is not only the result of farming activity. The various causes of coastal hyper sedimentationħ The silting of the table reefs is none other than the result of the activity practiced on the watersheds. In Polynesia, with a view to gaining space on the sea, the public authorities proceeded to landfill vast portions of the coast hence, in Tahiti, the airport takes over 20 to 25% of the total surface of the fringe reefs (Saffache, 2006). Although such excavation enabled the creation of road infrastructure, it induced a damaging and irreversible effect on the environment: retreat of the shoreline and advancement of silted areas for a lack of natural barriers (Saffache, 2002 ). It is evident that, once this material is compacted and dried, it produces very good quality hollow blocks. ![]() The considerable demand for construction materials chewed away the fringe reefs which were later excavated to obtain a “coral soup”. Coastal extensions, which were used for excavation, gradually diminished to the point of completely disappearing. ![]() Coral: highly esteemed construction materialĦ Present day coral reefs are particularly damaged for they are used for several economic activities for example they supply coral sand for building houses and roadways. A multi-faceted deterioration process 1.2.1. In France, coral mainly borders the islands of Martinique and Guadeloupe (Atlantic Ocean), Polynesia, Wallis & Futuna (Pacific Ocean) and Réunion Island and Mayotte (Indian Ocean). American, French and British nuclear testing (Bikini, Eniwetok, Mururoa, Fangataufa, the Christmas Islands, etc.) enabled the work to be completed since, before burying their nuclear charges in the coral bedrock, scientists were required to study their geological and mechanical characteristics.ĥ Being an inter-tropical coastal formation, the coral reef develops primarily in South-East Asia and more specifically in Indonesia and the Philippines 101 countries nevertheless benefit from these particularly rich ecosystems. These first works were followed at the beginning of the XXth century by numerous expeditions to the Australian Great Reef (the first in 1928). It is following a trip to the Pacific Ocean that Charles Darwin built his theory on ground subsidence and showed interest in annular coral formations (atolls). A few points to noteĤ Studies of coral reefs are recent, since 1848 is the date of the initial surveys. Although coral has existed for the past billion years, those which cover the seabed in the present day appeared in the Jurassic period (secondary era) and develop in the Atlantic, Pacific and Indian oceans (SCORE, 1998).Ģ Coral reefs support a broad range of marine biodiversity (one quarter of all fish caught throughout the world live near the reefs), causing researchers to estimate that reef disappearance would jeopardise world ecological and economic functions.ģ With a view to assessing the state of coral reefs in France (DOM-TOMs), a synoptic overview of deterioration will be presented, followed by a panoramic view of future perspectives. 1 Covering approximately 1.2 million km 2 or 0.25% of the world maritime domain, coral reefs represent the greatest structures formed on the earth’s surface by living creatures. ![]()
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