NEW ORLEANS – Hundreds of U.S. Geological Survey scientists were missing from the biggest conference in their field this month.

Typically, some 450 researchers from the nation’s top natural resources and natural hazards agency attend the annual meeting of the American Geophysical Union, the largest gathering of Earth, space and climate scientists in the world.

But in the weeks before this year’s conference, the Interior Department – which oversees the USGS – issued a new cap on attendance: No more than 199 employees across the department could travel to the meeting, and expenditures could not exceed $399,000.

As a result, just 178 USGS researchers were present at the AGU conference in New Orleans last week – a 60 percent drop from last year. In addition, 30 abstracts for posters or oral presentations, which take weeks to prepare, were withdrawn by USGS scientists who were unable to attend.

According to spokeswoman A.B. Wade, the USGS was not given a rationale for the policy shift.

A spokeswoman for the Interior Department said the decision to limit the number of employees saved hundreds of thousands of tax dollars. She said the larger number of employees who attended the meeting in past years were an example of the Obama administration’s “addiction to spending.”

But one USGS scientist who was denied approval to attend AGU just 10 days before the meeting said the crackdown on conference attendance amounted to the Interior Department “telling us we can’t do our jobs.”

“It’s in my position description that I am to conduct research and disseminate that research,” said the scientist, who asked not to be named out of concern for his job. ” When I had legitimate science and I had a budget to attend the meeting and I’m told I can’t go, that’s harassment.”

The scientist, who works in USGS’s Climate and Land Use Change mission area, has attended AGU most years since the late 1990s. He helped organize events at the conference, was slated to participate in multiple sessions and had already booked a plane ticket and reserved a hotel room when he was denied approval for his travel.

Typically, USGS researchers who wish to travel for a conference must apply via an online database. If the conference will cost more than $100,000, USGS officials then submit the requests to the Interior Department for approval.

The annual AGU meeting is the biggest geoscience conference of the year, featuring more than 22,000 scientists from all over the world, and USGS has spent hundreds of thousands of dollars to send roughly 450 researchers for the past several years. Attendees say the conference gives them an opportunity to share their research, meet with far-flung collaborators, find out about funding opportunities and keep up to date with the most advanced science and technologies in their fields.

Christine McEntee, executive director of the American Geophysical Union, called the drop in this year’s USGS attendance “troubling.”

“We’re concerned about it because there’s no better place [than AGU] for the U.S. to share the stellar knowledge and stellar research it has with the world,” she said.

Wade noted that this year’s meeting location in New Orleans (it is usually held in San Francisco) may have increased the cost of attendance for some researchers; the USGS has a large campus in Menlo Park, Calif., an easy commute to San Francisco.

But overall registration numbers were typical, and participation by other federal agencies didn’t drop by nearly as much, according to AGU. This year’s attendees included 252 scientists from the National Oceanic and Atmospheric Administration – roughly the same as last year – and 735 researchers from NASA, down 13 percent from 2016.

The limit on USGS conference travel also appears to have affected attendance at the annual meeting of the Geological Society of America, which was held this October in Seattle. Melissa Cummiskey, GSA’s senior director of meetings, said the number of USGS researchers at the conference was down between 40 and 45 percent from the previous year. Those researchers who were approved to attend found out just a week before the conference, Cummiskey said.

USGS and other Department of Interior bureaus could see major spending cuts in the coming year. This summer, Interior Secretary Ryan Zinke told a Senate panel that he planned to shed some 4,000 staffers from the department – about 8 percent of full-time staff. He also defended President Donald Trump’s proposal to slash Interior’s 2018 budget by more than 13 percent, saying “this is what a balanced budget looks like.”

Under the stopgap continuing resolutions that have covered government spending since September, the budget for USGS has remained relatively constant.

Meanwhile, the inspector general for the Interior Department opened an investigation in October into Zinke’s travel decisions and use of taxpayer funds. Documents obtained through open records requests have shown that Zinke paid $12,375 for a four-hour chartered flight from Las Vegas to Montana and spent more than $53,000 on three helicopter trips in summer.

Conference attendance by federal employees has been under scrutiny for much longer. Stricter policies for travel across the federal government were put in place in 2012 after a scandal at the General Services Administration. The inspector general for the GSA published a scathing report on a $823,000 Las Vegas conference that featured a mind reader and a $31,208 reception.

Marcia McNutt, who directed the USGS from 2009 to 2013, said the bureau argued strongly for the importance of attending AGU in the wake of that scandal and was able to send its normal contingent of scientists to the meeting. She noted that the president hasn’t yet nominated a USGS director, and the nominee for assistant secretary for water and science (the department official who oversees the bureau) hasn’t been confirmed.

“There’s no one there to advocate for the USGS when they need to go to an important meeting like this,” she said.

McNutt, who is president of the National Academy of Sciences, said the absence of USGS researchers from AGU represents hundreds of lost opportunities for government scientists – a statement the Interior spokeswoman called “hyperbolic.”

“AGU is just this incredibly exciting venue for people to learn from each other and be on the cutting edge,” McNutt said. “If you aren’t there, if you have to wait until all that gets published, you are in the backwoods of science. And all of those people who didn’t get to go are basically sitting there in the backwoods in the dark.”