#Status of Coral Reefs 2002 - International Coral Reef Action Network

Status of Southeast and Central Pacific Coral Reefs ‘Polynesia Mana Node’
BLEACHING EVENTS IN FRENCH POLYNESIA
There have been 7 bleaching events in French Polynesia over the last 2 decades, with
most of them in the Society Islands. There are good data for 4 of these events: 1991,
1994, 1998 and 2002. All these bleaching events were correlated with warm ocean sea
surface temperatures above 28°C, which is the normal summer maximum.
Temperatures were at least 1 or 2°C higher for days, sometimes for weeks during
months of warm waters. The most serious and best documented event occurred in
1991. It started in March, and by the end of the event in September 20% of coral
colonies were dead. In 1994, the bleaching was equally severe at the time, but most of
the colonies recovered and there was less than 5% mortality. These two events (1991
and 1994) were widespread throughout the Society and Tuamotu islands. The 1998
event was very patchy; one part of an island was bleached but not others, one island
was affected but not the next one. On some outer reef slopes in Rangiroa, coral
mortality was over 90% after a few weeks. The most recent event in December 2001
to January 2002 bleached corals on many Society barrier reefs and lagoons, and
generalised bleaching of outer reef slope corals started in March and corals were still
bleached in July (with about 10% mortality). The susceptibility of coral genera was
similar in all events e.g. in 1991 for Acropora, 100% bleached and 51%; for Montipora
it was 72% and 0%; for Pocillopora, 25% and 8%; and for Porites, 44% and 0%. The
apparently increasing frequency of bleaching events (every 3 years on average) poses a
major threat to the corals of this region, with the real risk that the more susceptible
species may become rare in the coral community.
Coral, sand and mangrove extraction for construction is resulting in damage to lagoons
and reef flat areas near urban centres, where there have also been major shoreline
modifications e.g. building of wharves, roads, airports, and seawalls for shoreline
protection. Coral and sand mining, although banned in Kiribati and French Polynesia,
still continue and these activities have resulted in the disappearance of beaches near
urban areas. In this way more than 50% of the coastline has been modified in the most
populated areas of the Society islands, with similar problems on Rarotonga, Cook Islands.
Sediment and sewage pollution from poor land management on the populated high
islands has damaged some reefs, but most impacts are local, and the sediments are readily
dispersed into oceanic waters. Only a few of the tourist islands have major sewage
treatment facilities, and human and animal wastes flow directly into reef lagoons. This
results in eutrophication in lagoons around Moorea, Tahiti and Rarotonga. No oil
pollution has been reported, except near the major harbours.
Tourism activities on some islands have resulted in major degradation to reefs during hotel
construction, and the industry is developing rapidly with 250,000 tourists per year visiting
French Polynesia, 60,000 to the Cook Islands and 25,000 to Tonga. Conflicts can arise
between operators and communities over access to lagoon and reef resources, especially the
fisheries, as well as well-recognised cultural impacts of too many tourists on islands with
low populations.
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