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Bleaching events are detected as whitening of the coral reefs in satellite imagery, and begin monitoring when they are deemed at-risk by NOAA’s Coral Reef Watch, as Bleaching Alert Areas on warning or higher.

The monitoring system allows users to observe where corals are bleaching throughout the world, ranging from no bleaching to severe, based on biweekly and globally comparable coral bleaching data.


Coral reefs provide a home to about 25 per cent of all marine species and are the most diverse of all the planet’s ecosystems, rivalling the diversity found in the Amazon rainforest. Estimates suggest that up to two million different types of animals thrive within or around coral reefs. Millions of people depend on that biodiversity for their livelihoods and food security.

Coral reefs are also one of the most sensitive ecosystems in the world, acting as a barometer for global warming.  For example, just a small rise in the temperature of the oceans will cause coral reefs to bleach and potentially die if the higher temperature is sustained.

Urgent action is needed to protect these vibrant underwater habitats from the effects of climate change, pollution, overfishing and other problems caused by people – such as cyanide fishing, coral mining and poor tourism practices.

The mapping and monitoring provided here by our partners at the Allen Coral Atlas, converts various sources of data on coral reefs to generate detailed maps, monitoring, images and notifications to support the implementation of coral reef and other ecosystem planning, as well as governance, evaluation, and management throughout Commonwealth countries.

For more information on these projects, please contact the Commonwealth Secretariat’s Blue Charter team. Email: [email protected] or visit the Blue Charter website