Celebrities push for environmental protection, seeking greater action on climate change.

The Beijing National Stadium, or Bird's Nest, switched off its lights on the evening on March 24, the first of more than 3,100 buildings in over 200 cities around China in support of Earth Hour, a global event started by the World Wide Fund for Nature.

"It's not only about switching off the lights for one hour, it's about lighting up people's awareness of environmental protection and calling on people to shoulder their responsibilities," says Chinese film star Li Bingbing.

Li is one of the ambassadors for the event, adding that the annual event encourages individuals, communities, and businesses to turn off nonessential electricity use for one hour.

According to the WWF, more than 250 ambassadors and influencers joined the movement around the world this year, including Li who has also appeared in Hollywood movies such as 7 Guardians of The Tomb and Transformers: Age of Extinction.

She was joined by Wang Junkai, a member of the popular Chinese band TFBoys, and Zhang Zetian, JD founder Liu Qiangdong's wife who became famous after a photo of her holding a milk tea at high school went viral online, and Wang Shi, founder of real estate giant China Vanke.

Thanks to the backing of celebrities, Earth Hour was observed worldwide, with more than 17,900 landmarks monuments switching off their lights.

When it started in Sydney in 2007, about two million people participated in the first Earth Hour event. The electricity saved then was enough to power 50,000 electrical cars for one hour.

Eleven years later, hundreds of millions of people now switch off their lights around the world from 8:30 to 9:30 pm local time on the last Saturday evening of March to show their commitment to environmental protection and urge greater action on climate change. Earth Hour is considered to be the largest global event relating to environmental issues.