Indonesian girls pose for photographs as they hold candles for the Earth Hour environmental campaign in Surabaya.
The 13th edition of Earth Hour, organized by green group 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."
"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.
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.
"Earth hour still is the world's largest grassroots movement for people to take action on climate change.
WWF's own "Living Planet" report in October said 60 percent of all animals with a backbone -- fish, birds, amphibians, reptiles and mammals -- 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, according to the organizers.
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.
Dubai achieved significant results in reducing electricity use during Earth Hour 2019. Dubai Electricity and Water Authority, DEWA, recorded savings of 267 megawatts, MW, in electricity consumption in the Emirate, equivalent to a reduction of 114 tonnes of carbon dioxide emissions.
Mankind will have used up its allowance of natural resources such as water, soil and clean air for all of 2019 by Monday, a report said.
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