As part of a seven-year series on the planet's most threatened ecosystems, this third episode takes an in-depth look at efforts to save coral reefs.

In the second year of a seven-year project, six presenters chart the fight to save the planet’s endangered ecosystems. In this episode, we visit Brazil, Cambodia and Kenya.

In the second year of a seven-year project, six presenters chart the fight to save the planet’s endangered ecosystems. In this episode, we visit the Maldives, USA and Greenland.