Jacinta Walsh said we could not have exponential growth on a finite planet.

"Australia works within an extractive system that is literally killing our chances of survival," she said.

"We need to reimagine a world we want to live in.

"We do not have time to wait for the government and corporations. They are never going to do what we need to do to survive. The system is geared solely towards exponential economic growth and expansion."

A Blockade Australia spokesperson said without mass organised civil resistance, Australia and its allies would not stop organising the exploitation of the planet.

"Sustained action that shuts down centres of political and economic power is the only effective means of forcing the political change required," the spokesperson said.

Meanwhile, two people blockaded Newcastle coal port yesterday by shutting down the rail line after jumping on top of, and then locking onto, a stopped train over a bridge crossing the Hunter River at Singleton in New South Wales.

This is the fourth action to disrupt the functioning of the port this week.

Kalpa Goldflam, 64, and Ayla, 16, brought the world's largest coal port to a halt with their protest.

Goldflam said the world as we knew it was continuing to hurtle towards ecological and climate collapse.

"I have climbed onto the train that was heading towards Newcastle coal port, the biggest coal port of the world and a key economic world fossil fuel gateway, to protest this system's inabilty to care about the survival of any form of life on the planet," she said.

"The growing network of Blockade Australia continues to hold the Australian system accountable for the current ecocide."