Coral reefs

Coral bleaching is a condition that can seriously damage and kill entire coral reefs. Corals contain microscopic algae called zooxanthellae that provide the coral with food and give them their vibrant colours.

Rising ocean temperatures cause corals to become stressed, and they expel the zooxanthellae and turn white or "bleach". If zooxanthellae do not return to the coral’s tissue, the coral will die.

As little as a 1° Celsius (1.8°F) increase in temperature above the summer maximum can cause corals to bleach. Tropical sea temperatures have increased by 1° Celsius over the past 100 years and are predicted to continue rising.

An example of this problem is Australia's world famous Great Barrier Reef, which lies off the state of Queensland. At around 1,243 miles long it is the world's largest reef.

The reef in the last years have experienced its worst ever case of coral bleaching, with over 60 percent of the reef being affected. Unless projected levels of climate change are slowed, much of the reef will be dead in decades. Deprived of their living homes, hundreds of species relying on the reef will also die out.

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