Cities around the world were turning off their lights Saturday for Earth Hour, with this year's event highlighting the link between the destruction of nature and increasing outbreaks of diseases like Covid-19.

In London, the Houses of Parliament, London Eye ferris wheel, Shard skyscraper and neon signs of Piccadilly Circus were among the landmarks flicking the switches.

“It’s fantastic news that parliament once again is taking part in Earth Hour, joining landmarks across the country and the world to raise awareness of climate change,” said Lindsay Hoyle, Speaker of the House of Commons.

“It shows our commitment to improving sustainability... and that we’re playing our part in reducing energy consumption,” he said.

In Paris, the three stages of the Eiffel Tour progressively went dark but there were few people to watch with the whole country under a 7 pm Covid-19 curfew.

The giant metal tower has been shut to the public since October 30, due to the pandemic.

In Rome, the lights went out at Rome’s 2,000-year-old Colosseum, while police enforcing Italy’s coronavirus movement restrictions checked the papers of a small crowd of onlookers. 

- Harmful human activity -

Asia had kicked off the event after night fell with the skylines of metropolises from Singapore to Hong Kong going dark, as did landmarks including Sydney Opera House. 

The Brandenburg Gate in Berlin and Moscow's Kremlin on Red Square also joined the annual initiative that calls for action on climate change and the environment.

After Europe, Earth Hour moves west to the Americas with the Empire State Building in New York, the Obelisk of Buenos Aires and the Rio's Museum of Tomorrow among venues dimming the lights.

For this year organisers said they want to highlight the link between the destruction of the natural world and the increasing incidence of diseases -- such as Covid-19 -- making the leap from animals to humans. 

Experts believe human activity such as widespread deforestation, destruction of animals' habitats and climate change are spurring this increase, and warn more pandemics could occur if nothing is done. 

"Whether it is a decline in pollinators, fewer fish in the ocean and rivers, disappearing forests or the wider loss of biodiversity, the evidence is mounting that nature is in free fall," said Marco Lambertini, director general of the WWF, which organises Earth Hour.

"And this is because of the way we live our lives and run our economies. 

"Protecting nature is our moral responsibility but losing it also increases our vulnerability to pandemics, accelerates climate change, and threatens our food security."

In Singapore, people at the waterfront watched as skyscrapers went dark and in a nearby park, Gardens by the Bay, a group of futuristic-looking tree sculptures had their lights turned off.

- 'Impact on environment' -

Earth Hour is about "more than just saving energy, it's more like remembering our impact on the environment," Ian Tan, 18, told AFP at the park. 

But he was not convinced the event, which has been running since 2007, made much of a difference.

"One hour is not enough for us to remember that climate change is actually a problem -- I don't really see (Earth Hour) as very significant," he said.

In Hong Kong, people at viewing points above the city watched as lights were dimmed on hordes of closely packed skyscrapers, while in the South Korean capital Seoul, the historic Namdaemun gate went dark.   

In Thailand, Bangkok's ultra-popular CentralWorld mall counted down to 8:30 pm before its exterior glass displays went dark for an hour -- though inside, the shopping centre appeared to operate as usual.