Fearing the continued erosion of even the most basic protections for food inspection, water quality and human health, Canadian scientists filled Ottawa’s streets in the Death of Evidence march. That theatrical mock funeral procession became something of a cultural touchstone. It was a turning point that galvanized public opinion against Prime Minister Harper’s anti-science agenda. By the next election, Justin Trudeau’s center-left government swept in on a platform that put scientists’ right to speak and the promise of evidence-based decisions alongside job creation and economic growth.

So here’s our advice as the Trump administration gears up. Spotlight and champion scientists’ refusal to kowtow to intimidation. I’m encouraged by what has already emerged: When Mr. Trump’s transition team circulated a questionnaire intended to identify staff members who had worked on climate change policies under President Obama, Department of Energy employees refused to release their names. When National Park Service employees were prevented from sharing information on social media, they created alternative Twitter accounts overnight and tweeted the truth about climate change and pollution from dusk to dawn.

Scientists who usually shy away from political engagement are condemning President Trump for handing the Environmental Protection Agency, the Department of Agriculture, the Department of Energy and the State Department to a group of men who have denied climate change or questioned the extent to which humans are responsible for global warming. Now scientists from across the country are planning a March for Science in the nation’s capital.

In some quarters, scientists advise their colleagues to remain quiet, keep their noses to the microscope and at most venture out to local meetings so that the “average voter” will know that they’re people, too, and that their work is valuable. But our experience leads to a different conclusion: Come together, speak up and speak out.

Scientists must recognize and fight political censorship, while they remain vigilant for political interference. Many federal science agencies have rules against political meddling in the scientific process. And whistle-blower protections provide federal (and some state) scientists with an additional safety net to report unethical suppression of scientific information. Researchers should confirm that reports they submit are the same as those published, and if changes have been made for political reasons, let the public know.

Share documents widely and back up data in a secure location if the administration politicizes or interferes in research. Encrypted chats, phone calls from home lines and face-to-face meetings can help spread information without the fear of political meddling. Speaking out, especially through scientific organizations, tells colleagues they need not be afraid. The warmth of community staves off the chill of censorship. Don’t let science be silenced.

Evidence and objective reality are the foundation of successful policy and governance. Openness is as vital to science as it is to democracy. We cannot allow hard-won knowledge to be ignored or distorted. To fight the snuffing of the light of scientific inquiry, learn from your neighbors to the north. Reject interference. Stay vigilant and stay vocal. In other words, stay scientists.