<p>Coral reefs are in trouble across the globe as rising greenhouse gas levels warm the oceans and boost the acidity of seawater. Pollution and overfishing make matters worse. Browse this gallery to see photos of healthy and degraded reefs around the world.</p> <p>Here, waves break over a coral reef off the coast of Mahé, the largest island in the Seychelles. The island nation is made up of some 115 tropical islands in the Indian Ocean.</p>

Coral Reef, Seychelles

Coral reefs are in trouble across the globe as rising greenhouse gas levels warm the oceans and boost the acidity of seawater. Pollution and overfishing make matters worse. Browse this gallery to see photos of healthy and degraded reefs around the world.

Here, waves break over a coral reef off the coast of Mahé, the largest island in the Seychelles. The island nation is made up of some 115 tropical islands in the Indian Ocean.

Photograph by Roberto Schmidt, AFP/Getty Images

Ocean Reefs

See photos of both healthy and degraded coral reefs around the world.

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