NEW YORK - New York's Empire State Building, Egypt's pyramids, London's Big Ben and Rio's Christ the Redeemer statue were among the world's most renowned monuments plunged into darkness for an hour on Saturday as part of a global campaign to raise awareness about climate change and its impact on the planet's vanishing plant and animal life.

The 13th edition of Earth Hour, organized by green group World Wide Fund for Nature, or WWF, saw millions of people across 180 countries turn off their lights at 8:30 pm to highlight energy use and the need for conservation.

The event comes after some of the most dire warnings yet on the state of Earth's natural habitat and species.

"We are the first generation to know we are destroying the world. And we could be the last that can do anything about it," WWF said.

"We have the solutions. We just need our voices to be heard."

WWF-Australia CEO Dermot O'Gorman said that "Earth hour still is the world's largest grassroots movement for people to take action on climate change".

"It's about individuals taking personal action but joining with hundreds of millions of people around the world to show that not only do we need urgent action on climate change but we need to be protecting our planet," he added.