Polynesian Reef

The Polynesian coral reefs: Preservable sweetheart

In the last fifty years, humanity has irreversibly damaged 20% of the world' s hard corals and 50% of the world' s rich corals are at stake over the next 20 years. Polynesia is characterized by particularly robust, sound canyons. Here the impacts of climatic changes are minimised and contamination is under our fingertips.

Except for the Marquesas Isles, all Polynesian archipelago have sea eco-systems consisting almost entirely of corals. Because of biogeographic factors, the reefs are certainly less biodiverse than in the tropics in the western Pacific. With almost 200 corals, 1200 types of sea life, 1000 types of shellfish and 2500 types of molluscs - to name only the most frequently known groups - these eco-systems are, however, still very wealthy in comparison to the moderate areas.

An area of reef contains a number of flora and fauna that are similar to the whole of the French coastline or the State of California. One of the most evident tasks of a reef is to provide a protection wall around the coasts that enables the creation of man-made activity along the coast.

The landmass of an igneous tunnel is composed entirely of reefs. There are 83 of them in Polynesia, 76 of which are in the Tuamotu Islands. In addition, the reef creates natural resource useful to humanity, such as conventional fisheries, acquaculture (i.e. oysters that make Tahiti's renowned pearls ) and the collection of decorative species that are loved by aquarium enthusiasts.

Then, of course, coastline and undersea reef paradise with hot, clear waters are perfect for tourists, making it the number one tourist destination in the state. The overall value of reef produce on the Moorea Islands is put at 85 million dollars per year (9 billion francs/74 million euros).

In addition to the financial quantifiability, the corals offer other precious characteristics that are not considered usable, such as the culture, society, tradition and spirit of the local populations who have been dependent on the reef for many years. The two major natural determinants that monitor the condition of our islands' endemic corals are cyclone and Acanthaster planeci (or Tahiti's Taramea).

The most common cyclone on the west edge of Polynesia happens to influence everything in its course, even the reef coasts that are subject to the waves of the wind. For yet to be determined reason, the 76 Tuamotu Island avocets have been exempt from this kind of incursion.

Last part of a 2004-2010 observed Tariamea assault destroyed most of the external reefs within the Society Islands. Recreational life in Polynesia, however, is fast and resistant to stress. Approximately a ten year is necessary for the corals to fully recover from these ailments.

Part of the culprit is to do with the issue of climatic changes. Corals are very susceptible to seawater temperatures and often live in an area that is very near their maximal tolerances. Before being bleached, the corals take on fluorescent colours for a few long days. A further aggravating effect is climatic changes, i.e. acidsification caused by an increasing amount of CO2 in the air and seawater, as this is continuously taken up by the oceans.

If the CO2 level climbs, the state of the chemicals changes, which in turn raises the level of acid in the sap. Calcification of sea creatures (including corals) interferes with the lime stone production. Today, anthropogenic activity is the major cause of the reef damages seen over the last 50 years.

Overexploitation, effluent discharges, over-sedimentation due to the carelessness of land vegetation and changes in the coastal line (rock faces, slopes for a particular use, etc.) are the major stress ors to which corals are exposed. Because of its remoteness in the Pacific Ocean, which provides some resistance to changes in physics and chemistry, because of the very wide spread of more than 5 million square km2/2 million square miles of island area and because of the relatively different climatic conditions, the French Polynesian sea corals seem to be somewhat sheltered from the dangers of cycling.

Although the temperatures have been crossed several occasions over the last 25 years, the incidence of bleach has been much less severe than in other parts of the globe, where corals sometimes reach 100% of the reef population. Locally, disturbances are confined to some of the most densely settled areas and have not yet arrived in the surrounding area.

The reason for this is not a fixed and methodological control of the ecosystem, but a restricted or non-existent population ( "more than a fourth of the island are uninhabited"). Finally, the barriere corals near most island are isolating and preserving the reef. Because of all these factors, 90% of the 15000 square kilometres /6000 square metres of corals and pelagic areas in the 118 Polynesian isles are still regarded as ecologically healthy.

Ifremer, IRD formerly Orstom, Malardé Institute, University of California, Berkeley, University of France Polynesia), France-Polynesia profits from a high-performance research institution that focuses on the island's surrounding area. In this context, researchers from four archipelagos have been observing the reefs' state of repair in Polynesia for more than 40 years.

The two research sites Gump/UC Berkeley (USA) and Criobe (France) also make it the best place to monitor the island's coral canals. The coral cliffs were formed in 1983 and are still in use today. Since 1991, Criobes Polynesia Mana Surveillance Programme has been carrying out a major evaluation of the status of strategic mana coral canals.

Bioindicator data on marine and marine populations for each target reef area are gathered every two years on almost 15 archipelagos distributed throughout the geographic area of Polynesia. Together with research on reefs, this observation makes it possible to comprehend how eco-systems work and develop over the years.

In the last fifty years, humanity has irreversibly damaged 20% of the world' s hard corals and 50% of the world' s rich corals are at stake over the next 20 years. Polynesia is characterized by particularly robust, sound canyons. Here the impacts of climatic changes are minimised and contamination is under our fingertips.