If the White House has its way, in 2018, 5.8 billion dollars will disappear from the budget of the National Institutes of Health—the largest funder of biomedical research in the U.S. That cut, which was revealed as part of President Trump’s budget proposal last Tuesday, represents 18 percent of the NIH’s budget. It has been described as “a significant blow to medical research” that would “set off a lost generation in American science.”

It’s also unlikely to actually happen.

“Presidential budgets are a statement of presidential priorities but Congress makes the decision—and there’s strong bipartisan support for the NIH,” says Tom Cole, a Republican congressman from Oklahoma, and chair of the House subcommittee that oversees the NIH’s budget. That support was evident earlier this month, when Congress totally ignored Trump’s proposal to slice $1.2 billion from the NIH for fiscal year 2017, and instead awarded the agency an extra $2 billion. “This is the second year in a row that NIH has received a substantial increase, and the intention of Congress is that that continue,” says Cole.

A $2 billion windfall is clearly better than a $1.2 billion shortfall, but that extra bolus of money is not the obvious bonanza that it seems. Congress may be holding back the Trump administration’s desire to cut funding for scientific research, but the threat of such cuts still looms. And in that atmosphere of uncertainty, it’s hard for agencies like the NIH to work out how to effectively channel money into research.

The problem is that good science takes time. Projects can take years to come to fruition, which is why the NIH only ever awards grants for two to five years—never just one. And the money for, say, a three-year grant isn’t doled out in one fell swoop. Instead, it’s allocated on a yearly basis, which means that it’s highly susceptible to fluctuating budgets. Imagine that the NIH commits all of its extra $2 billion for 2017 to new three-year grants. If the agency is hit by a $5.8 billion cut in 2018 or 2019, those new grants would wither. Researchers would have to stop their work, and fire newly-hired staff. That $2 billion would effectively have been thrown away.

The agency can’t reserve the money for future years, either. All of it has to be spent within fiscal year 2017, which ends on September 30th. This means that when NIH staff heard about the extra $2 billion at the start of May, they had only five months to work out how to spend it all. “It’s chaos figuring out how to move this money,” a source at the agency tells me. It could go towards new equipment, supplemental funding for existing grantees, or bridge funding to tide established scientists over between grants. “But it’s just small chunks here and there,” the source says. “There’s no way we could fund a full project.”

One could argue that this is a lot of ungrateful hand-wringing. They did, after all, get more money. And as Cole has said, and as Congress has signaled, Trump’s drastic cuts may never materialize. But that’s no reason for complacency, argues Harold Varmus, a Nobel laureate who was NIH director from 1993 to 1999. Most of us think that Congressional appropriators, happily fond of NIH, will not allow the cuts to happen,” he says. “Still, it would be foolish to assume that we will be saved without an effort to defend ourselves.”

Here’s the thing: Even if Trump’s cuts never take place, their very proposal creates a climate where funding agencies can’t make the best use of the resources they already have, or think strategically about the future. In that environment, “what happens is we become more conservative,” an NIH staffer tells me. The agency gravitates towards safe projects from well-known researchers. “It really hurts younger scientists who have less of a reputation, or a portfolio of research.”

And although the President’s budget may just be a suggestion to Congress, it’s a moral document. It tells the world about America’s priorities, and in this case, it says that science isn’t one of them. “It’s a signal to young people who are thinking about biomedical careers,” says Cole. Why would a young researcher choose to pursue a postdoctoral stint in the U.S. when looming cuts—no matter how unlikely—would quickly leave them without a job? Why not pursue a position in another country, where research funding is stable and predictable? Indeed, the new French president Emmanuel Macron has already taken advantage of this turmoil by attempting to seduce American scientists to move to France.

“My colleagues and I have been advocating for a five-year rolling funding plan for the NIH, aiming for steady increases to keep ahead of inflation,” says Varmus. The U.K., for example, pledged last year to gradually grow government funding for science by about 20 percent over the next four to five years. The U.S. did something similar in 1998, doubling the NIH budget over five years. But after that golden period, funds failed to keep up with inflation and the agency lost 22 percent of its purchasing power between 2003 and 2015. In recent years, lawmakers have once again started to push for bigger budgets, with Newt Gingrich calling for another doubling in 2015.

“We need to have steady, predictable increases,” says Cole. He is hopeful that the White House will come to appreciate that. “As major figures in the administration learn more about this, they’ll understand that at some point, they’ll have a major pandemic on their watch. When that happens, you don’t want to have cut funding for the NIH or the CDC. You don’t restore that capacity overnight. Cuts in this field will come back to hurt us in the future.”