The emerald ash borer, Agrilus planipennis, is never furloughed. Native to Asia, this insect is an invasive species killing beloved ash trees across North America.

“It’s sweeping like fire through timber,” said Jeanne Romero-Severson, a plant geneticist at Notre Dame, who has been working with the Forest Service on a breeding program to create an insect-resistant ash tree.

She had been planning to meet with colleagues to discuss the bad beetle at an annual U.S. Agriculture Department invasive species conference scheduled to be held last week. But then came the partial government shutdown. The conference was canceled, even as nature marches — and hops, crawls, wriggles and oozes — onward.

“The invasion continues. The trees continue to die,” Romero-Severson said. “We’re losing time we cannot recover.”

The most severe costs of the shutdown may be these invisible ones — the loss of relatively obscure activities by a massive federal bureaucracy with responsibilities that stretch into unexpected corners of society. The costs of not doing this work doesn’t translate neatly into a dollar figure or a percentage of economic growth chipped off the gross domestic product. And it’s hardly as tangible as long lines at the airport or long waits to get questions answered by the IRS. But it is the hard-to-fathom toll of telling hundreds of thousands of people with expertise to stay home.

That means canceling training for wildland firefighters, law enforcement and Border Patrol agents. Research grant proposals go unreviewed. Safety checks of sports stadiums are postponed. Efforts to improve election security are put on hold.

Much of the government work that is not considered essential during a shutdown, and thus not labeled “excepted” under agency shutdown plans, involves nonurgent but important activities. As the Trump administration rushes to preserve vital functions, it’s the type of work that attracts little attention. But those involved say that while it may be hard to measure, letting these efforts lapse will have a long-term cost.

One worrisome area, for example, is cybersecurity. The threats are mounting as the government tries to stave off digital attacks and secure elections processes in advance of the 2020 election. But the Department of Homeland Security’s shutdown plan called for furloughing more than 1,500 of the 3,500 employees in the newly formed Cybersecurity and Infrastructure Security Agency, or CISA.

“We’re under attack every day from very sophisticated nation-states like Russia, China, North Korea and Iran. They get better every day. And we’re not. We’re in a holding pattern,” said Suzanne Spaulding, a Homeland Security undersecretary during the Obama administration in charge of cybersecurity and infrastructure protection.

“We are in a race with our adversaries, with the bad guys, on innovating in cyberspace. It is a challenge when you have a full team, when all hands are on deck. And all hands are not on deck,” she said.

CISA issued a brief statement about staffing levels: “Due to the lapse of appropriations, CISA has ceased a variety of critical cybersecurity and infrastructure protection capabilities. However, we have maintained baseline operational capabilities supporting national security, including staff in the National Risk Management Center, in accordance with DHS and OMB guidance.”

Medical science and pharmacology are also fields that evolve rapidly and require government regulation. At the Food and Drug Administration, the pipeline for new drug approval has slowed. Staffing has shrunk because of the shutdown.

The FDA review for a new drug for treating peanut allergies in children has been delayed by the shutdown. Drugmaker Aimmune Therapeutics said the shutdown has pushed back the timeline for its federal regulatory approval until the end of this year.

Doctors nervously watch for signs of significant delays with new treatments.

“You have to worry,” said Dr. Walter Curran Jr., executive director of the Winship Cancer Institute of Emory University.

Another concern: wildfires. They’ve been getting worse in the western U.S., and the past two years have seen particularly horrific fires that consumed hundreds of thousands of acres and killed scores of people. About 200 federal workers who were set to begin training to fight forest fires last week in Colorado Springs were forced to drop out because of the shutdown. Many of them hoped to join fire hotshot crews.

Another training session in Tennessee also was canceled. The missed training means many of them will not be qualified to help fight forest fires or can’t move on to become crew bosses or incident commanders.

There’s already a shortage of wildland firefighters, said Wendy Fischer, executive director of the Colorado Wildland Fire & Incident Management Academy.

“This situation sets people back. And we’re coming up on fire season,” she said.

The shutdown obviously doesn’t help the economy. A top White House economist this week said the economic impact from the shutdown would be twice as great as previously estimated. But the numbers, even if they involve multiple billions of dollars, remain fairly modest compared to the vast scale of the U.S. economy.

That said, the shutdown has the potential to deliver a psychological blow to the country that could send the economy reeling, economists have warned.

“Broadly it’s more like an economic corrosive rather than a cliff event. It’s wearing down the economy and sentiment, confidence, people’s optimism. At some point the corrosive will eat through the foundations of the economy and the economy will break, but no telling when that will happen,” said Mark Zandi, chief economist for Moody’s Analytics.

The broader business community likes predictability and reliable data, notes economist Robert Shapiro, who was an official in the Department of Commerce during the Clinton administration. He said the Bureau of Economic Analysis — an agency with data so sensitive that it puts officials in a locked room to review numbers that could jolt the markets — is not putting out valuable monthly reports during the shutdown.

“What’s happening in home construction? What’s happening in manufacturing orders? What’s happening in retail sales? What’s happening in exports and imports? Do you know we don’t know what the trade deficit is, in November? Trump can’t even know if his trade tariffs are working!” Shapiro said.

And so the U.S. economy is “flying blind,” as he put it on the Brookings Institution website.

“The decisions proceed with a lot more guesswork than usual, because they don’t have the data, and in those cases you’re more likely to have bad decisions, and that impairs the efficiency of the economy,” he said.