[00:09] Coral reefs are one of Earth's most biologically diverse ecosystems, and one of the most threatened by changes in climate and human activity.

[00:18] Covering less than 1% of the planet's surface, these 'tropical rainforests of the sea' are home to nearly one million species of life; one quarter of all species in the world's oceans.

[00:30] Humans depend on coral reefs for their abundant fish, medicines and tourism. Reef structures also shield coastal areas from erosion and storm damage.

[00:40] Today, these extremely fragile underwater communities are rapidly being damaged or destroyed, from the use of cyanide and dynamite to catch fish, to warming global temperatures that heat ocean waters.

[00:53] Located in shallow, tropical waters, the color and life of coral reefs have been literally fading since the late 1970's through a process known as coral bleaching.

[01:04] Bleaching occurs when heat expels the algae that supply coral with nutrients and vibrant color. Without the algae, coral reefs cannot survive.

[01:13] As sensitive indicators of environmental stress, the demise of coral reef ecosystems is a stark reminder of how human activities are impacting Earth's environment.

[01:24] For Our Changing Planet, I'm Jane Joyce. Visit us on the web at www.umac.org/ocp.