Labour groups, First Nations leaders, students and environmentalists led the rally calling on the federal government to do more to combat climate change and to focus on creating more jobs in the renewable energy sector to shift Canada away from an oil-based economy.
The rally came on the eve of both the Climate Summit of the Americas and the Pan American Economic Summit, which the provincial environment ministry said in a release demonstrates "the important link between climate action and a strong, prosperous low-carbon economy."
The crowd grew into the thousands during the march.
David Suzuki, a prominent environmental activist, says he was excited by the fact that such a wide range of groups were involved in the demonstration, not just environmentalists. He added the economic impact of climate change is going to be "incredible" and "catastrophic" unless more is done by the federal government.
Canadian author and activist Naomi Klein said elected officials need to treat climate change as an "emergency" by reducing carbon emissions and investing in greener jobs. She said a "broader agenda" is emerging against climate change that involves more than just traditional environmentalists because the economic model tied to fossil fuels is failing Canadians on many different fronts.
Fonda, 77, called the rally "historic" and "very important" due to the coalition of different social and union groups that were in attendance. The actor and activist added that ending the use of fossil fuels in Canada is not mutually exclusive from a prosperous economy and that more jobs can be created in the renewable energy sector.
"I'm here because I think that the coalition that is represented in today's march and rally, and not just today but ongoing in Canada — First Nations, labour unions, working people, students — this is the kind of coalition that will make the difference," Fonda said.
"The best people to get it out are the people living on the front lines, the workers, who work in places like the tarsands and the fracking industry ... The labour unions that represent oil and gas workers, they are here, I mean that's amazing that's historic, this is what we need to win.
"More and more we're going to see this kind of coalition."
Suzuki said that Canada is probably more vulnerable to the impacts of climate change than any other developed nation, and said that the federal government is sacrificing the environment in the name of profit.
"What government that says the economy is its highest priority can continue for over 10 years to ignore climate? If they really care about the economy then they've got to focus on that because the economic implications of climate change are catastrophic," he said.
"The problem we face in North America is that our agenda is being driven by corporate interests. Our governments, in Canada and the United States, act as if what's good for corporations is good for Canada — the corporations have a very different agenda."
Klein said that if there was more of a focus in Canada on an economy tied to environmental protection and renewable energy, the country would be able to create many times more jobs than we have currently in the fossil fuel sector.
"Our governments are nowhere near where they need to be. Their pledges, their emission reduction pledges, are not in line with what scientists are telling us," she said.
"If we take the science seriously we need to be cutting our emissions by about eight per cent a year, that's not going to happen out of what we're hearing at those official summits," she added.
"So what's happening in the streets is we're pushing but we're also leading, we're leading with our solutions."
Also on HuffPost