"We've laid out these hundreds of pairs of children's shoes to give that message, for a fairly COVID-safe protest," Ms Melloy said.

"Many people in XR are grandparents and very middle-class, very law-abiding people stepping up to the game.

"So we just wanted to do an action that was at the other end of the spectrum, so very law-abiding, more of a vigil."

Ms Melloy said both of them still believed in the XR ethos of disruption to get attention, and had been arrested for breaking the law at other protests.

Mr Cruickshank said multiple scientific reports clearly showed delaying action on climate change would worsen the lives of future generations significantly.

New research published earlier this month found heatwaves had become more frequent and longer lasting in Australia and globally, in an accelerating trend.

The shoes were laid out in concentric circles, each pair side by side, with several Extinction Rebellion flags in the centre and messages written on paper and cloth along several pairs of shoes.

"Our children and their children are, in all probability, going to have a worse life because of climate change than we do," Mr Cruickshank said.

"Things are on the decline if we don't do something about it."