The head of one of Australia’s largest environment groups has warned Extinction Rebellion protesters they could be creating division on environmental issues at a time when “cool heads” are needed.

Lyndon Schneiders, national campaigns director for the Wilderness Society and a veteran activist, told Guardian Australia he hoped the XR campaign would not hand more power to the fossil fuel lobby by causing further polarisation.

This week, XR groups in Australia and around the globe have stepped up activities, with an “international rebellion” that, in Australia, has focused on disrupting city centres.

Play Video 0:53 'The arrests make a point,' say Extinction Rebellion protesters in Australia – video

Other leading environmentalists said they strongly supported the XR movement, saying it was playing an important role in raising the alarm on the climate crisis.

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Dom Rowe, program director at Greenpeace Australia Pacific, said: “This gives us hope … we welcome any group that’s out there mobilising. We are in a climate crisis with heatwaves, parts of the north being smashed, and with farmers suffering from drought.

“Yes XR is going to create inconvenience, but they are telling people what to expect. It is totally acceptable what they’re doing. XR knows our politicians are asleep at the wheel.”

The XR in Australia wants the government to “tell the truth by declaring a climate and ecological emergency”, to halt biodiversity loss and cut greenhouse gas emissions to zero by 2025, and to create a “citizens’ assembly”.

Schneiders, who started out as a forest activist more than 25 years ago, said it was clear “business as usual” had not delivered for the environment and there was always a role for public protest.

It won’t be all happy days and windmills Lyndon Schneiders

But he said while the society did not have a formal position on XR, he saw potential pitfalls from the XR movement’s activities, which he said were being rolled out in a country that had become “pretty conservative” after Coalition governments were returned in seven of the past nine federal elections.

“Australians are not idiots and most believe that climate change is real and happening, but they also understand that there will be pain and disruption in that change and it won’t be all happy days and windmills,” he said.

“We’re wealthy and have a heavy exposure to commodity markets. A lot of Australians understand change has to come but they worry about impacts on their standard of living. I feel we have to keep that in mind when we are working through strategies.”

“It isn’t the role of the environment movement to say yes or no to things, but by the same token I would urge a degree of caution. We are all worried about another 10 years of business as usual, but when groups like ours and others plan campaigns, we have to build a really big tent with a lot of the community onside.

“I am not telling them not to do this, but we are getting to a phase where there’s a sense of despair starting to creep in and some genuine fear. This is not a bad time for cool heads.”

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One Extinction Rebellion principle is to mobilise at least 3.5% of the population to achieve “system change”, saying “no regime in the 20th century” had been able to push back against movements of that size.

But Schneiders doubts the evidence for that claim, saying while it might apply in the UK where XR was born, he doubts it would apply in Australia.

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“We need to build on how Australians are worried, and show that we are providing hope for that majority. XR has I think gone past that and decided we don’t have that time.

“In a democracy if you don’t have a significant part of the community really supporting your actions then you are potentially going to create further polarisation that won’t lead to the results that XR wants to see. I would encourage them to think about that in the context of Australia.

“More Australians will probably be engaged and support some of their demands, but also there are incredibly powerful vested interests that want the status quo, and I hope XR does not give them more power.”

Christine Canty, a neuropsychologist from Melbourne and a spokesperson for XR in Victoria, said disrupting commuters in major Australian cities was only a part of their tactics, and that the fossil fuel industry and politicians were also being targeted.

“We know we need to take tactics that will step things up. We know mass civil disobedience is the thing that will bring social change.

“We don’t know if this will work but, for me personally, I look at the evidence base and if it tells me that this is what will change things then as a scientist that’s what I’ll do because we don’t have more time to work that out.”

Jono La Nauze, chief executive of Environment Victoria, said: “Civil disobedience won’t win this alone, but I hope XR’s role is in raising that alarm and waking more people up to the fact that we have a disaster on our hands.”

Kelly O’Shanassy, chief executive of the Australian Conservation Foundation, said: “It’s completely understandable that people are becoming so frustrated by government inaction that they would choose to protest in ways that can be disruptive.”

She said the “bold strategy” could backfire, but “my sense is it won’t because Australians want our governments to take climate action and that’s Extinction Rebellion’s No 1 demand.

“Community unrest will most likely continue escalate until the government acts.”

She said there were “many ways to make positive change”, adding: “Extinction Rebellion has chosen to support peaceful civil disobedience. Children have chosen to strike from school en masse.

“In the end, all approaches will be important to get the big changes we need to build a safe future.”