Earth Hour, an annual event aimed at highlighting energy conservation, attracted more support than ever across the capital on Saturday - but not without a dose of criticism too.

Major landmarks in 85 Chinese cities, including the Bird's Nest in Beijing and sections of the Great Wall, were pitched into darkness between 8:30 pm and 9:30 pm to raise awareness of the need for environmental protection.

In Wangjing, roughly 2,000 residents signed a board pledging their commitment to protecting the planet, while advertising displays at more than 70 shops were switched off. "We also held a costume show to raise awareness of choosing environmentally friendly materials when buying clothes," said a worker in Wangjing's area management office who gave only his surname as Liao.

At the Bird's Nest, the country's iconic national stadium, music fans enjoyed a power-free concert using flashlights.

This year marks the World Wildlife Fund's fifth Earth Hour, and although many joined in with its promotion events, others were more skeptical about its impact.

"Earth Hour is a environmental show that is not environmental at all," Fang Zhouzi, a famous writer known as a "science cop" for his battles against pseudoscience, wrote on his Sina micro blog.

"The one-hour blackout doesn't lead to energy conservation or emissions reduction. If candles are used, the emissions are increased and the environment is polluted."

Some netizens even speculated that the activity could even damage the State grid. "Zhou Peng'an" on Sina claimed the power interruption and recovery causes great fluctuations and may paralyze the entire network.

However, Songshuhui, a science promotion organization, explained through its micro blog that the power used for lighting accounts for just 10 percent of China's electricity, therefore the blackout has little impact.

"The aim of the (Earth Hour) campaign is not to save a certain amount of power. It intends to develop the public's habit of turning off unwanted lights and attain a demonstration effect," Yang Fuqiang, director of the WWF's global climate change solutions program, was quoted as saying by Beijing Times.

Earth Hour involved more than 4,000 cities in 134 countries and regions this year. Participating Chinese authorities promised to "extend the one hour" and make real changes, with 18 cities in Henan province pledging to plant at least 50,000 trees every year to protect the Yellow River.

Dalian will also invest 10 billion yuan in planting 340 million trees.

Well-known companies are also making efforts. Apparel brand Marccasne promised to increase the use of organic cotton by 15 to 20 percent in 2011, while automaker Volvo plans to cut carbon dioxide emissions from its trucks by 13 million tons over the next three years.