Corals are tiny invertebrate animals, called polyps. Generally found in shallow waters of the tropics, they live symbiotically with single-celled microalgae, zooxanthellae, which provide them with nutrients and much of their colour. Each coral secretes a limestone skeleton around itself; as it grows, it divides, forming colonies and eventually, a coral reef. Individual coral colonies can live for thousands of years.
Coral reefs are among the most biologically diverse ecosystems on earth. Although they cover less than 0.2% of the oceans, coral reefs are estimated to harbour as many as a quarter of all marine species. For example, the Great Barrier Reef, off northeastern Australia, harbours some 1,500 species of fish and 4,000 species of molluscs. As pointed out by UNEP’s World Conservation Monitoring Centre (In the Front Line
, 2006), coral reefs provide all four types of ecosystem services, as defined by the Millennium Ecosystem Assessment
: i.e., coastal protection from storm surges and waves Provisioning
: i.e., fisheries, pharmaceuticals, construction materials Cultural
: i.e., tourism, spiritual and aesthetic appreciation Supporting
: i.e., nutrient cycling, nursery habitats
While cautioning about the limitations of economic valuation techniques, this study cites estimates of the annual economic value of reefs at US$ 100 000 to 600 000 per km2. Certainly some locations depend on the services of coral reefs more than others; some 90% of small island developing States (SIDS), for example, have coral reefs, and many depend on their services to a great degree.
Coral reefs are also among the most vulnerable ecosystems on Earth. According to a status report by the Global Coral Reef Monitoring Network, as of 2004, 20% of coral reefs had been destroyed worldwide, 24% are in imminent danger, and a further 26% are threatened over the longer term (Status of Coral Reefs of the World: 2004 Summary
). While the main threat to coral reefs is human pressure in the form of inappropriate land-management, fishing, and coastal development, coral bleaching, as a result of global climate change, is considered one of the greatest threats. A global literature review, conducted by the Australian Government in 2006, revealed that substantial impacts of global climate change on marine life are already apparent, and that recent warming of tropical waters has led to repeated mass coral bleaching events on the Great Barrier Reef and elsewhere.
Over the past decade, coral bleaching has increased substantially both in extent and severity, becoming a particularly serious global problem that threatens marine and coastal biodiversity. One of the main causes of coral bleaching is increased sea surface temperatures, as a result of climate change. A prolonged temperature increase of as little as 1 or 2° C above average can disrupt the relationship between polyps and zooxanthellae, resulting in a loss of nutrients and photosynthetic pigments, leaving the coral tissue transparent and revealing the white skeleton beneath. Eventually, corals weaken and may die.
In 1998, at its fourth meeting, the Conference of the Parties (COP) drew attention to an extensive, severe coral bleaching episode occurring that year as a result of abnormally high water temperatures. Recognizing the potentially severe loss of biological diversity and consequent socio-economic impacts, and noting this occurrence as a possible consequence of global warming, in link decision IV/5
, the COP requested the Subsidiary Body on Scientific, Technical and Technological Advice to analyse this phenomenon and provide relevant information to the fifth meeting of the COP.
At its next meeting, in decision V/3
, the COP decided to integrate coral reefs into programme element 2 (marine and coastal living resources) of the programme of work and requested the Executive Secretary to integrate fully the issue of coral bleaching in the programme of work on marine and coastal biological diversity and to develop and implement a specific work plan on coral bleaching, in cooperation with the United Nations Framework Convention on Climate Change and with relevant conventions and organizations. The COP also noted that there was significant evidence that climate change is a primary cause of the recent and severe extensive coral bleaching, and that this evidence is sufficient to warrant remedial measures being taken in line with the precautionary approach.
In decision VII/5
, the COP adopted an elaborated programme of work on marine and coastal biodiversity and included under programme element 2, on marine and coastal living resources, a list of suggested activities on coral bleaching, and physical degradation and destruction of coral reefs. A Specific Work Plan on Coral Bleaching and Elements of a Work Plan on Physical Degradation and Destruction of Coral Reefs, Including Cold Water Corals were adopted as appendix 1 and 2, respectively.
The following activities of the Specific Work Plan on Coral Bleaching
recognize the urgent need to implement action to manage coral reefs for resistance and resilience to, and recovery from, episodes of raised sea temperatures and/or coral bleaching:
1. Management actions and strategies to support reef resilience, rehabilitation and recovery
2. Information gathering
4. Policy development / implementation