In January 1970, the organizers of the first Earth Day published a full-page ad in The New York Times. A few months ahead of thousands of demonstrations and teach-ins across the United States, they declared that Earth Day represented “a commitment to make life better,” “to provide real rather than rhetorical solutions,” and “to challenge the corporate and government leaders who promise change, but who short change the necessary programs.” They continued, “April 22 seeks a future.”

Nearly half a century later, the scientific community is once again issuing a call to action. When the world commemorates the 48th Earth Day this weekend, the occasion will be marked by March for Science rallies nationwide and around the globe. At a time when facts and science are under attack, the organizers hope to send a loud and clear message that “science is a vital feature of a working democracy.” Denouncing policies that “threaten to further restrict scientists’ ability to research and communicate their findings,” they warn that “we face a possible future where people not only ignore scientific evidence, but seek to eliminate it entirely.”

One of the most threatening of those policies is in President Donald Trump’s budget blueprint: a cut of nearly $6 billion to the National Institutes of Health. As The Washington Post reported last month, the proposal would slash roughly a fifth of National Institutes of Health’s funding in fiscal year 2018, “a seismic disruption in government-funded medical and scientific research.” The administration also has proposed a separate $1.2 billion reduction in the remainder of this year’s National Institutes of Health funding, along with severe cuts to the National Science Foundation, the Environmental Protection Agency and other programs, to pay for a border wall and higher defense spending.

When news of the proposed National Institutes of Health cuts broke, scientists expressed fear about the far-reaching implications. In addition to biomedical research conducted at National Institutes of Health headquarters in Maryland, more than 80 percent of the institutes’ budget is used to fund research at universities and other institutions nationwide. In many cases, its grants account for most of a laboratory’s funding, and they often drive follow-on contributions from other sources. In 2016, for example, National Institutes of Health distributed more than $23.5 billion in grants to support research on everything from cancer to Alzheimer’s to mental health to blindness.

The budget proposal also “breaks with a history of bipartisan support for federally funded science,” as The Post reported. Indeed, it was one of the bipartisan triumphs in this country’s history to agree on the importance of scientific research in driving progress. Just last year, despite persistent gridlock in Washington and a divisive presidential campaign, Congress approved an increase in the National Institutes of Health budget with strong bipartisan support.

And though the Republican Party is clearly guilty of advancing an anti-science agenda, especially when it comes to climate change, it has been encouraging to see members of both parties speak out forcefully about the importance of fully funding the National Institutes of Health. For example, Rep. Tom Cole, R-Oklahoma, an influential member of the Appropriations and Budget committees, called the proposed cuts “very shortsighted,” adding that biomedical research is “part of the defense of the country.” Rep. Jamie Raskin, D-Mayland, a progressive House freshman who represents the district where National Institutes of Health is headquartered, described slashing the its budget as “indefensible.”

Nonetheless, the debate over National Institutes of Health funding is further evidence of what has been clear for quite some time: Science is now political. In response, scientists are becoming more political, too. The March for Science is merely the most visible manifestation to date of an emerging social movement built on the common-sense principle that scientific findings should inform policy and not the other way around. It will be followed later this month, on Trump’s 100th day in office, by the People’s Climate March. Meanwhile, the recently formed group 314 Action is recruiting and training members of the scientific community to run for Congress, prioritizing races against members of the House Science Committee who are working to advance anti-science policies.

While some politicians would have us believe that we can’t spare money for scientific research, the opposite is true. We can’t afford to defund the vital efforts that could help solve some of our greatest challenges, from cancer to climate change. Those who plan to attend the March for Science — who are not just progressives or Democrats but represent an ideologically and culturally diverse movement — know that science is for all. They are sending an unequivocal message that while science may have become political, it will never be negotiable.

Katrina vanden Heuvel is editor and publisher of the Nation magazine.