With Prime Minister Justin Trudeau announcing the federal government's approval of the Trans Mountain pipeline expansion Tuesday, environmentalists wasted no time sending their message to Ottawa with hundreds of anti-pipeline protesters gathering downtown Vancouver.

"If he really cared about his kids and about the future … then he would be not worrying so much about the financial situation," said demonstrator Lynda Dernisky, who lives in Delta. "He would be caring about the planet. There's only one planet – no Plan B."

George Rammell, another protester, vowed to fight the pipeline expansion "till it's dead."

"I think it's disastrous for the planet," he told CTV News. "I think that we're going back into the dark ages here. Really, it's just the wrong decision."

"I've already been arrested," Rammell added. "I would do it again, sure."

The protest, organized by the Coast Protectors and Wilderness Committee, got underway at 5:30 p.m., starting at Georgia and Hamilton streets.

The demonstration was set to move along Georgia before turning on Granville, the Nelson and Hamilton.

By 6 p.m., upwards of 250 dissenters had gathered. The crowd started moving at around 6:30 p.m.

Footage from the scene showed demonstrators carrying signs with anti-pipeline messaging on them, including "Future biologist: Please keep the planet alive so I can have a job (and a life)" and "The answer is still no."

Peter McCartney of the Wilderness Committee believes if the project is approved, the federal government will face opposition throughout the province, and Tuesday night’s protest may just be the beginning if the pipeline is approved.

"My message to the federal government is you can go ahead and try, but communities are prepared to fight you at every step," he told CTV News ahead of the protest. "If they do put shovels in the ground, I expect to see people standing in the way."

Pipeline proponents also held a small rally of about two dozen people outside the Vancouver Convention Centre, chanting “build that pipe,” and wearing T-shirts that read “the world needs more Canadian energy.”

Graham Wilson from Port Moody got into a spirited debate over jobs and the environment with a couple young women who disrupted the rally.

“[The pipeline expansion] gives a lot of jobs and opportunities,” Wilson said, adding that the fact that it’s taken the better part of a decade to get to this point means to him that “the whole government system we have is a failure.”

Cliff Sampare of the Gitxsan First Nation said he supports the pipeline expansion primarily because of the jobs and economic benefits he believes it would bring.

“It’s not that we have a stake or not,” Sampare said. “We do have family…all over the place looking for work.”

Not a great turnout for the pro #TransMountain expansion rally. Really just a couple dozen folks and some curious tourists. And one dude who’s anti pipeline blasting his music and trying to crash their event. @CTVVancouver pic.twitter.com/1RYJAtv3li — David Molko (@molkoreports) June 18, 2019

Okay the yelling has stopped and it’s evolved into a conversation that seems somewhat constructive.. well.. sort of. @CTVVancouver pic.twitter.com/O9vYT1s2wv — David Molko (@molkoreports) June 18, 2019

The federal government announced its plans for the controversial pipeline expansion between Alberta and Burnaby early Tuesday afternoon following a cabinet meeting and after markets close for the day.

Ottawa bought the pipeline last year for $4.5 billion dollars but the project was shelved nine months ago after the Federal Court of Appeal outlined concerns about Indigenous consultations and the impacts more oil tankers would have on marine life off B.C.’s coast. Ottawa ordered more study on both matters.

Trans Mountain Canada says there are still a number of regulatory and commercial steps that would need to be taken before construction can restart.