The former archbishop of Canterbury, Rowan Williams, has backed pupils who have been taking part in school strikes to protest over climate change and who are planning to join a “climate rebellion” next month, warning that the ecological crisis means “the future of the human race is now at stake”.

Williams, whose stark comments come amid a growing wave of protests over the scale of the ecological crisis, said non-violent civil disobedience should have “wide and deep” support from the public.

“The nature of changes in climate and environment that we are living with threaten not only the wellbeing but also the being of our species on this planet in the long term – and in the middle term they threaten some of the most vulnerable populations on Earth,” he said.

More than 100,000 pupils are planning to walk out of lessons in 60 countries on Friday as part of the schools strike movement. And in April thousands of “concerned citizens” are expected to descend on London for a campaign of mass civil disobedience designed to bring widespread disruption to the capital.

Rowan Williams video message.

In a video message in support of the April event, organised by Extinction Rebellion, known as XR, Williams said: “It is not surprising people in this urgent situation feel they have to take non-violent direct action – they have got to find a way of putting the case for the human race before those in power. That is what Extinction Rebellion [is] doing, that is what the Friday [school] strikes are doing.”

XR, which has the support of hundreds of academics and scientists, is demanding the UK government tells the truth about the ecological crisis and enacts legally binding policies to reduce carbon emissions to zero by 2025. It also wants a citizens’ assembly to oversee the transformation to a sustainable economy.

The group closed London bridges in November, and this time it intends to bring widespread disruption to London until its demands are met.

There is growing evidence of the scale of the climate emergency. Last year a UN report said there were only 12 years left to avoid the worst impacts of climate breakdown from floods and heatwaves to food shortages and huge numbers of climate refugees.

Williams added: “I believe a wide and deep support from the public is needed to bring this matter fully to the attention of our political leaders. To show we can actually achieve democratic change for the good of everybody.”