Last weekend’s March for Science brought a renewed sense of purpose and urgency to Earth Day — and the momentum should carry on at Saturday’s People’s Climate Movement March. Collectively, these mass demonstrations — the March for Science alone attracted more than 15,000 people to DC and thousands more in satellite cities — send a clear message that President Trump’s full-scale assault on the basic tenets of science on numerous fronts is among his most unforgivable sins of willful fiction. It is heartening that people are willing to take to the streets to defend the primacy of civilization’s most effective tools for establishing what the facts of the case really are in this strange age of aggressive alts.

For Canadians like me, the March for Science, in particular, brought not just encouragement but a sense of déjà vu, tinged with relief. For President Trump is not the first chief executive of a major Western nation to wage a war on science. Until Stephen Harper’s Conservative government was voted out of power in 2015, it spent nearly a decade as the free world’s chief aggressor on this front. Under Harper, the Canadian government waged a steady attack on science and data the administration deemed unnecessary or unhelpful to its agenda. Harper cancelled the long-form census — the government’s most important data-gathering tool — and slashed budgets for climate science programs. He mothballed vital environmental research labs and rewrote environmental protection legislation in the fine print of budget bills.

The Department of Fisheries, a frequent regulatory opponent of the oil and gas projects Harper’s government was pushing, saw some of the deepest cuts: When it was forced to shutter the majority of its libraries, books full of irreplaceable research wound up in dumpsters. Media access to government scientists working on climate and environmental topics all but vanished, and in several egregious cases individual scientists were directly muzzled, forbidden to speak at all in public about their work. Harper also pulled Canada out of the Kyoto treaty and became a notorious heel dragger at international climate talks.

In the summer of 2012, in the wake of the introduction of Harper’s most aggressively anti-science budget, a few hundred protesters marched from an Ottawa conference center hosting a biology symposium to Parliament Hill, in a protest styled as a mock funeral for the Death of Evidence. As in the March for Science last weekend, many of the Ottawa marchers were working scientists who’d never before participated in a protest. Many wore white lab coats to signal their allegiance to a set of principles long assumed to be above the partisan fray.

Five years later, the Canadian government and its institutions are back in the hands of leaders who respect the scientific method and value the expertise of scientists on their payrolls (and beyond). Granted, the American war on science promises to be a much meaner and more reckless battle than the Canadian one, led as it is by a president and administration whose erratic, know-nothing tendencies are without analogue in any democratic nation, ever. (Stephen Harper, despite his many sins, respected the basic tenets of democracy and had a knowledge of what government was for that extended beyond last night’s Fox News broadcast.)

Still, the Canadian war holds some useful lessons as America’s defenders of science transition from their first fledgling protest to the longer fight.

1) Marching was the right way to start

There is a scientific angle to every public policy debate, but science rarely stands on its own as a political issue. And because science is everywhere in modern society, embedded in nearly every aspect of daily life, it is often taken for granted. And because scientists generally don’t think of their work as subject to the whims of a given administration or legislative body (in much the same way we don’t think of the weather as being susceptible to such whims), they are not usually well organized to respond to direct political attacks. For all these reasons, as Canadians learned in the aftermath of the Death of Evidence march, a street protest is an excellent way to catalyze a movement in defense of scientific principles when they are under attack.

Protest marches are typically used to push an issue up toward the top of the public agenda and to pressure politicians, but in the case of science, advocacy is really only a small part of their utility. Far more important, at least in the Canadian case, was the value of a march as an organizing tool. The Death of Evidence march in Ottawa attracted fewer than a thousand people and caused merely a minor media stir. But it triggered a three-year campaign that steadily built resistance against the Conservative government’s cuts to research funding, its silencing of government scientists, and its intransigence on climate policy.

Scientists needed the catalyst of the march to nudge them out of their labs and create a political arena of their own; once unleashed, they proved to be a potent force. In 2012, Harper’s Conservatives were at the zenith of their power in Canada, gleefully slashing science budgets amid punditry proclaiming a permanent rightward shift in the country’s politics. The march of the lab coats seemed a noble but futile gesture. Cuts to obscure research programs were far off the media radar and low on opposition party agendas. Yet a mere three years later, Harper’s hostility to inconvenient truths helped topple his government. It’s telling that one of the first and most wildly popular initiatives of Justin Trudeau’s new government in 2015 was to reinstate the long-form census and several other data-gathering and research initiatives that had been mowed down in Harper’s anti-science onslaught.

2) Marching is only a start. The biggest challenges are still to come.

It’s encouraging that American scientists and their supporters have been so quick to take to the streets in opposition to Trump’s nascent war on science. It’s crucial now that the fledgling movement continue to organize and grow. This was the real long-term value of the Death of Evidence march — it helped launch a nationwide network of activist and advocacy groups to track the government’s meddlings and muzzlings, share information, and maintain steady pressure on the government and on opposition parties to keep science on the agenda.

This started with the march’s organizers, who formed a permanent organization called Evidence for Democracy. But it came to include formal and informal networks on university campuses and in think tanks across the country. Not only did this create a platform for continued action against the war on science, but it gave the media a go-to voice any time the issue came up — one that couldn’t be easily dismissed. Science was too broad a category to be smeared by hard-right partisans, and beyond those partisans, it turns out, people invest a lot of credibility in the unified statements of scientists. Claiming space in the public domain – on campuses and in political forums, in the press and on social media – is the necessary next step in the resistance to Trump’s war on science. Citizens are more eager to see this happen than scientists likely expect.

3) Science can be a winning wedge issue because no one wants to be against it

One of the first clear signs that Prime Minister Harper — who had ignored not just protest but all dissenting opinion for much of his six years in power — had heard the calls from the street in 2012 was a shift in tone in the way he discussed new pipeline projects. His government’s gutting of Canada’s environmental regulations in its spring 2012 budget – the casus belli for the Death of Evidence counterattack — was widely understood as an effort to streamline approvals for big energy and resource projects. But by August, Harper was insisting the approvals would be “decided scientifically.” His cabinet ministers added similar lines to their talking points. A very calculating regime decided there was no upside to being seen as anti-science.

On the braying surface of it, Donald Trump would appear to care little for such niceties. His hostility to not just science but verifiable facts of all sorts is well documented. But take a closer look at the rote statement Trump issued on Earth Day. Read past the silliness about how “economic growth enhances environmental protection” to see what he says in the third paragraph: “Rigorous science is critical to my Administration’s efforts … My Administration is committed to advancing scientific research.”

Now, I’m certain Trump didn’t write that statement, and it’s highly likely he didn’t even read it before it was released under his name. Still, someone in the Trump White House knows that there’s real political danger, long term, in being too contemptuous to science in general. (Also of note: Rick Perry, who barely understands his own job, felt obliged to tweet out support for Texas’ wind industry on Earth Day.)

A boilerplate paragraph in an instantly forgotten official statement clearly doesn’t signal any real change in the Trump administration’s staggering hostility toward the EPA and climate science and the National Institutes of Health. But it does hint that Trump’s minions understand that beyond his evidence-deficient alt-right base, most Americans think of science as a positive thing. Exploiting this wedge between immediate sledgehammer policy goals (building pipelines, for example) and the broader worldview and base of support was crucial to the success Canadian scientists had in putting the war on science on the public agenda. If scientists can make it clear they are not just another Democratic/liberal/loser protest voice in the chorus of Trump’s opponents but a distinct group arguing that attacking science is bad for everyone, they will help their cause a great deal.

4) Personal stories and small, specific absurdities are more powerful than fact sheets and dramatic outrage

As Vox’s David Roberts has argued eloquently, climate change campaigners have learned by now — or should have — that you will not be able to truth-bomb your way to political victory over opponents who are in thrall to an entirely distinct reality, a reality untethered to observable phenomena. Piles of facts, reams of data, careful analysis, thoughtful conclusions — all the stuff of actual science is useless on this battlefield. This is a war of images and emotions and tribal allegiances.

In Canada’s war on science, much of the vital momentum the pro-science movement built — including a huge slice of the media coverage it received — came via individual scientists telling heartfelt stories about their experiences and journalists detailing the small, striking absurdities being endured. The government’s decision to order Department of Fisheries scientist Kristi Miller not to speak about a major 2011 paper on declining salmon populations kept her out of the press for a couple of days. But her story soon supplied incontrovertible evidence of governmental interference, involving officials at the highest levels of government. It would be told and retold dozens of times.

The small and specific triumphs and outrages are the stories that stick with people. Very few Canadian scientists were ever directly muzzled by the Harper government, but the few like Miller who were became flashpoints. A crazy story about the bureaucracy spending an entire day debating whether it could offer a comment on an innocuous news report about a new government study on the varying causes of snowfall mattered as much as reports on the loss of multimillion-dollar research labs. The traction already gained by the brief, exhilarating run of rogue tweets about climate change from the Badlands National Park Twitter account shows the same dynamic at work in Trump’s war on science. It’s absurd to try to silence a National Park. Most Americans understand that absurdity, even in Trump’s America. Exploit that.

5) Follow the data. And archive it.

In the midst of the media air war, there is vital behind-the-scenes work to be done to save irreplaceable data and research and find safe haven for it until Trump’s war is over. This was something many Canadian scientists didn’t realize until it was too late, and the government was already shuttering Department of Fisheries libraries and piling research files into garbage bins. Preserving or duplicating the data is valuable for its own sake — and is something American government scientists already realize and have begun to act on — but it’s also a powerful publicity tool. Destroying data is as egregious an affront to the most basic Enlightenment values as is book-burning. And if that destruction is made visible to the public, it’s damning. Exploit that, too.

6) The good guys in the lab coats will win the war

When scientists took to the streets of Ottawa in 2012, it was a very dark time for Canada. We were climate pariahs, our scientists showing up at international conferences of their peers with government communications staffers in tow, lest they stray too far from the party line. Canada’s government was in the hands of what one National Research Council scientist I interviewed for my book The War on Science likened to small-town hardware store merchants, uninterested in any knowledge that didn’t produce cash on the barrel.

Donald Trump, of course, is much, much worse — an incurious, self-absorbed man-child surrounded by calculating zealots of all the nastiest stripes. There are already casualties. Canadian universities and tech companies are already finding that the world’s best and brightest are being drawn north of the border by Trump’s assault on science and reason. Stephen Harper didn’t like his government producing data and reports that ran counter to his policy goals; Trump seems contemptuous of knowledge itself.

Still, this is maybe the most important lesson of Canada’s war on science for those fighting the one now underway in Trump’s America: You will win. Science will win. It may incur some grave wounds along the way, but in the end, science will endure in what remains the world’s leading nation for advanced research and technological development. And a government that openly embraces the knowledge now scorned may soon(ish) come to power. Science may even come back stronger than ever. Here in Canada, no one had ever cheered the long-form census until it got taken away. Now that it’s back, it’s being treated like a national treasure. In as little as three years or so, let’s hope, your data-gatherers and scientists, too, will be greeted as liberators.

Chris Turner is the author of The War on Science: Muzzled Scientists and Willful Blindness in Stephen Harper's Canada and four other books on climate change, sustainability, and technology. His new book on Canada's oil sands and the future of energy will be published by Simon & Schuster in September. He lives in Calgary. Twitter: @theturner.

The Big Idea is Vox’s home for smart discussion of the most important issues and ideas in politics, science, and culture — typically by outside contributors. If you have an idea for a piece, pitch us at thebigidea@vox.com.