Dozens of companies around the world said they would take part in this year's campaign, which also saw Singapore's skyline go dark and Hong Kong turn off the lights along Victoria Harbour.

In New York, the riverfront United Nations headquarters turned black, as did the Brandenburg Gate in Berlin and Saint Peter's Basilica in the Vatican.

Other global landmarks that flicked the switch included Sydney's Opera House, the Eiffel Tower and Arc de Triomphe in Paris, Dubai's Burj Khalifa - the world's tallest skyscraper - the Acropolis in Athens, Shanghai Tower and the Kremlin building in Moscow.

WWF's own "Living Planet" report in October said 60 percent of all animals with a backbone had been wiped out by human activity since 1970.

In Cali, Colombia, people lit candles to form a "60+" sign as part of the Earth Hour events.

Another study said a recent decline in bugs that fly, crawl, burrow and skitter across still water - fueled by deforestation, urbanization and the rise of commercial farming - was part of an unfolding mass extinction event, only the sixth in the last half-billion years.

Last year, Earth Hour was observed in more than 7,000 towns and cities in 187 countries.

While the lights-off event is a symbolic gesture, Earth Hour has led successful campaigns over the past decade to ban plastics in the Galapagos Islands and plant 17 million trees in Kazakhstan.

Agence France-Presse