To watch part two click here

Filmmakers: Tanya Peterson and Nick Turner

For most people Australia is a very long way to go for a holiday, yet every year hundreds of thousands of tourists from Europe, America and Asia head "down under".

At the top of the list of things "to do" once they get there is the Great Barrier Reef.   

The Great Barrier Reef is the largest natural structure on earth and listed as a world heritage site. But like so many of the earth's treasures these days, it is under threat.

The tiny organisms or polyps that manufacture the coral are threatened with extinction from increasing average water temperatures caused by global warming.

Governments around the world have been responding to a United Nations report that warns of the need for an urgent action on climate change, to avoid irreversible damage to the planet.

John Rumney cares passionately about the reef. He has been coming here for over 30 years and now runs a dive company specialising in eco-tourism.

Tanya Peterson and Nick Turner went to Australia to document the effects of global warming on one of the world's most beautiful and delicate ecosystems.