Crows defender Kris Massie knows he must be switched on this weekend when he takes to the footy field.

But Saturday night (March 29) at 8pm he will be "switching off" for Earth Hour.

Earth Hour is an international environmental initiative which calls on cities around the world to turn their lights off for one hour in a powerful visual statement to generate awareness about the need to tackle climate change and reduce greenhouse gas emissions.

Every capital city in Australia is taking part as well as a host of major international cities including San Francisco, Washington DC, Chicago, Manila, Copenhagen, Bangkok and Christchurch.

Kris Massie is urging all Adelaideans to support the environmental cause and switch off their lights from 8-9pm next Saturday night.

"While turning lights off for an hour is a symbolic gesture, it can have real significance in terms of making individuals, communities and especially businesses aware of the actions they can take in their homes and workplaces to conserve energy can help reduce greenhouse gas emissions," Massie said.

"Every day we can take action to help reduce the city’s greenhouse gas emissions.

"Just a simple measure such as turning the TV off at the wall instead of keeping it on “standby” or switching the lights off when you leave a room can have an impact."

The event is an initiative of WWF (World Wide Fund for Nature) and took place for the first time in Sydney, March 2007, resulting in 2.2 million people and 2100 businesses turning off their lights for one hour. This was equivalent to taking 48,000 cars off the road for that hour. This year millions of people around the world will take part in the event.