IUCN, the International Union for Conservation of Nature

First, ocean warming is directly reducing coral cover through coral bleaching. Reef-building corals contain plant-like organisms called zooxanthellae that live symbiotically within their tissue. Zooxanthellae provide their coral host with food and oxygen and in return, the zooxanthellae receive nutrients, carbon dioxide, and an enemy-free shelter. This symbiotic relationship evolved tens of millions of years ago and has been critical to the success and evolutionary radiation of corals and to the development of reef ecosystems. When summertime water temperatures are just a degree or two warmer than usual for a few weeks, this critical yet delicate symbiotic relationship breaks down and the zooxanthellae are expelled, often leading to the coral’s death. (The greater the magnitude or duration of the warming, the greater the mortality and effect on coral populations.) The phenomenon is called “coral bleaching” because the coral animal appears to turn white after the zooxanthellae loss. This is because without their zooxanthellae symbionts, which contain various photosynthetic pigments, corals are nearly transparent and the white, external calcium carbonate skeleton that the coral polyps live on becomes plainly visible.

Coral reefs and tropical marine ecosystems are facing increasing stress from a variety of causes including over-exploitation, land-based sources of marine pollution and severe events including storms and tsunamis. They are also highly vulnerable to climate change, with 16% of the world’s reefs suffering serious damage during the global bleaching event of 1998. Climate Change is now recognized as one of the most serious long-term threats to the biodiversity and services provided by tropical marine ecosystems. The effects of climate change are visible today and predictions for coral reefs are extremely dire with many experts predicting the functional extinction of many coral reef systems during this century.

Globally, the economic and social importance of coral reefs has been acknowledged and it has been recognized as the first ecosystem to face 'irreversible changes' under the global temperature increases that are expected. Because of the great socio-economic importance of coral reefs, especially to the tourism and fisheries industries, the loss of these ecosystems would perturb the livelihoods of hundreds of millions of people around the world. As a result, the coral reef management community is engaging with the need for greater understanding, improved monitoring, management, and public awareness of the growing threat of climate change to coral reefs and dependant communities and sectors.  

Both science and management practitioners are racing to develop knowledge and tools in order to limit the vulnerability of reefs to climate change and support their complex socio-ecological structure.

Recognizing the highly dynamic nature of science in this area, the growing risk of climate-induced bleaching and the growing need for sound advice to management, this working group was formed in 2006, on a grant from the John D. and Catherine T. MacArthur Foundation, within the IUCN Global Marine and Polar Programme to facilitate the reciprocal flow of information between scientists and managers to continually update and improve recommended management practices for mitigating climate change threats to coral reefs.

At government and inter-governmental levels, policy outputs from the working group will seek to inform at the highest levels the possibilities of mitigating climate change impacts on coral reefs and thereby empower management efforts at local, national and regional levels.

The goal of the working group is to establish a baseline survey, raise awareness and foster capacity building for the implementation of a sustainable management of coral reefs worldwide. The working group seeks to draw on leading practitioners in coral reef science and management to streamline the identification and testing of management interventions to mitigate the impacts of climate change on coral reefs. The working group consults and engages with experts in three key areas: climate change and coal bleaching research to incorporate the latest knowledge; management to identify key needs and capabilities on the ground; and ecological resilience to promote and develop the framework provided by resilience theory as a bridge between bleaching research and management implementation. 

Coral polyps can reproduce either by budding or sexually. During the mating season, corals release sperm and eggs into the water. When both sperm and eggs meet they will form a free swimming larva that will attached to a concrete substrate, generally a coral reef. Subsequently the coral will form its surrounding shell by combining carbon dioxide  with calcium. They living in colonies and therefore forming this accumulation of limestone known as coral reefs. An interesting fact about corals is that they are host, within their tissue, to a symbiotic unicellular algae known as zooxanthellea; which accounts for the coloration of coral reefs due to pigments contained by the symbiotic algae. Zooxanthellae provide their coral host with food and oxygen and in return, the zooxanthellae receive nutrients, carbon dioxide, and an enemy-free shelter. This symbiotic relationship evolved tens of millions of years ago and has been critical to the success and evolutionary radiation of corals and to the development of reef ecosystems. This symbiosis requires a shallow and clear water for an optimal growth and development of coral reefs. When the environmental conditions are not adequate (e.g. water temperature rise), that can lead the zooxanthellae to produce free radicals triggering the coral polyp to release its symbiont; this phenomenon is known as coral bleaching because the coral animal appears to turn white after the zooxanthellae loss. Indeed, without their zooxanthellae symbionts, which contain various photosynthetic pigments, corals are nearly transparent and the white external calcium carbonate skeleton that the coral polyps live on becomes plainly visible. If the situation last too long it will eventually lead to the coral death as illustrated bellow.

Coral reefs, along with seagrass beds, mangrove habitats and other tropical marine environment, support the highest marine biodiversity in the world. More than 500 million people worldwide depend on them for food, storm protection, jobs, and recreation. Their resources and services are worth an estimated 375 billion dollars each year, yet they cover less than 1% of the Earth’s surface.

Nevertheless, these ecosystems are facing increasing stress from a variety of causes including over-exploitation, land-based sources of marine pollution and severe events including storms and tsunamis.

They are also highly vulnerable to climate change, with 16% of the world’s reefs suffering serious damage during the global bleaching event of 1998. Climate Change is now recognized as one of the most serious long-term threats to the biodiversity and services provided by tropical marine ecosystems.

The effects of climate change are visible today and predictions for coral reefs are extremely dire with many experts predicting the functional extinction of many coral reef systems during this century. According to the Status of Coral Reefs of the World-2004, 70% of the world coral reefs are threatened or destroyed, 20% of those are damaged beyond repair, and within the Caribbean alone, many coral reefs have lost 80% of coral species.

Ocean warming is directly reducing coral cover through coral bleaching. Globally, the economic and social importance of coral reefs has been acknowledged and it has been recognized as the first ecosystem to face 'irreversible changes' under the global temperature increases that are expected. Because of the great socio-economic importance of coral reefs, especially to the tourism and fisheries industries, the loss of these ecosystems would perturb the livelihoods of hundreds of millions of people around the world. As a result, the coral reef management community is engaging with the need for greater understanding, improved monitoring, management, and public awareness of the growing threat of climate change to coral reefs and dependant communities and sectors.