On Monday the activist group Extinction Rebellion blocked bridges across Canada in Halifax, Toronto, Kitchener, Ont., Edmonton, Vancouver and Victoria.

While the climate action group may have been relatively unknown until now, they've been expanding rapidly around the world.

Here's a rundown on the group and what they're calling on governments to do.

What is Extinction Rebellion?

Extinction Rebellion (XR) was launched by Roger Hallam and Gail Bradbrook on Oct. 31, 2018.

It was formed after the Intergovernmental Panel on Climate Change's Special Report: Global Warming of 1.5 C that said policymakers have only 12 years to stop global catastrophic climate change .

The Burrard Street Bridge in Vancouver was adorned with protest banners on Monday morning, as protesters with Extinction Rebellion demanded global leaders do more to combat climate change. Bridges and viaducts in half a dozen other Canadian cities were also blocked by protesters as part of a co-ordinated, worldwide effort. (Maggie MacPherson/CBC)

The group is also concerned about findings that suggest we have entered the sixth global mass extinction event . Its symbol is an hourglass in a circle that represents time running out.

How big is Extinction Rebellion?

The group says that its first protest in 2018 drew 1,500 people to Parliament Square in London. It has spread now to more than 60 countries with 350 local groups .

According to their website, there are more than 30 XR groups across Canada, with both local and provincial groups.

What is it demanding and from whom?

Extinction Rebellion has three primary demands of governments, that they:

Declare a climate and ecological emergency.

Act immediately to stop the loss of biodiversity and reduce greenhouse gas emissions to net zero by 2025.

"Create and be led by the decisions of a Citizens' Assembly on climate and ecological justice."

What kind of tactics does XR use?

According to the group , it "uses nonviolent civil disobedience" to stop the mass extinction of life on Earth and "minimize the risk of social collapse."

Writer and activist George Monbiot is also a strong supporter of XR. Speaking from London with CBC News, he said one of the reasons he supports the group is because it's unlike anything he's ever seen before.

"It's really the first movement in my life that's been of sufficient scale to address this issue," Monbiot said. "I've been an activist and journalist in this field for 34 years, and there've been lots of movements coming and going, and a lot of them have been great … but none of them has reached this scale and this impact."

What are some supporters saying?

"It sucks. I really don't enjoy being here. I don't like blocking a bridge, and I don't like being in conflict with police," said Kevin Imrie, one of the organizers of the XR Toronto group. "I have a job, and I don't want that to be challenged in any way. I have a life that I live, and I'm not someone who enjoys conflict. But I sincerely believe that if we just wait to do a once-a-year climate march, it's not going to make a God damn difference."

Imrie said that he understands why people, like motorists, might get angry, but he hopes they get angry with governments for not doing enough to reduce carbon emissions and protect biodiversity.

Protesters stopped at the corner of Burrard and Pacific streets in Vancouver before occupying the bridge. (Andrea Ross/CBC)

"Our collective building is on fire," Imrie said. "The house is on fire, and I hate to say that, because that sounds like something a climate activist would say, but genuinely, it is a crisis and should be treated that way."

Monbiot also stressed the need for rapid action.

"We are facing the biggest predicament that humankind has ever encountered, which is the rapid collapse of our life support systems," Monbiot said. "And unless we step up and respond to this huge predicament with a huge mobilization, it's just going to continue."

Why has this movement caught on so quickly?

Laurie Adkin, a professor at the University of Alberta's department of political science, said that it's unclear why XR has grown so quickly. But she has a few ideas why it could be. One is that we're seeing an older generation of climate researchers and people concerned over climate change taking part after decades of inaction. And she also said that XR might have some staying power, simply because the human race and biodiversity is at the end of its rope.

"I think it has a lot of growth potential, because the crisis we're facing is truly an existential one," said Laurie Adkin

But one of the challenges is the risk involved in taking part in XR's actions.

A protester is taken into custody in Toronto on Monday. (Mark Bochsler/CBC)

"I must say, [some] tend to forget that civil disobedience means you're willing to be arrested. You're breaking the law, right?" Adkin said. "There is a really high cost for individuals … it's not an action that many people can easily join in."

But, she added, if it's done on a large scale, it's more effective, since authorities can't arrest everyone.