LONDON (Reuters) - British naturalist Sir David Attenborough first visited Australia's Great Barrier Reef in 1957, scuba-diving in its crystal clear waters along with an array of species.
Nearly 60 years later, the 89-year-old returns to the world's largest coral reef for a new television series, exploring the spectacular ecosystem.
"The Great Barrier Reef with David Attenborough" sees the broadcaster aboard the 56-metre (184-foot) Alucia research and exploration vessel, which features a state-of-the-art Triton submersible, laboratories and a helicopter.
"The huge privilege there was on this trip ... 60 years after my first one, is that we had this extraordinary technology," Attenborough told Reuters.
"You just sit there ... and in front of you there is the water. You aren't breathing it, you're not looking through a glass or porthole, or anything, you're just surrounded by water. ... And all these fish come swimming by."
Last summer, a heritage committee of the UNESCO cultural agency said the reef's outlook was poor due to threats like pollution and climate change, but it stopped short of listing it as "in danger".
"The biggest danger for the reef at the moment is the one which comes from international sources ... the increase in temperature of the water and the increase in acidity of the water," Attenborough said.
"If the temperature goes up two degrees, the consequence will be that a very large number of species of coral will die. And so the reef is in real, real danger and it is going to take international cooperation to deal with that."
Attenborough has been making television documentaries for decades, traveling all over the world.
"I would like to think the programs I've made ... have done something to spread an understanding of the natural world," he said. "People who watch them may realize not only what a wonderful world we have inherited, but the danger that it is in."
That danger, he said, is largely due to overpopulation.
"The best solution is that the people of the world ... would have the right to determine how many children they have," he said. "They have the social right, the medical right and the educational right to do that."
"The Great Barrier Reef with David Attenborough" airs on Britain's BBC One this Christmas.
Reporting by Holly Rubenstein; Writing by Marie-Louise Gumuchian; Editing by Mark Trevelyan