Interior Secretary Ryan Zinke testifies during the Senate Energy and Natural Resources Committee hearing on the proposed FY2018 budget request for the Interior Department. (Michael Reynolds/European Pressphoto )

Interior Secretary Ryan Zinke told lawmakers Wednesday that he plans to shrink his department’s sprawling workforce by 4,000 employees — about 8 percent of the full-time staff — as part of budget cuts to downsize the government’s largest public lands agency.

Zinke, testifying before a Senate panel on the White House’s proposed budget for the Department of the Interior for fiscal 2018, said he would rely on a combination of attrition, reassignments and buyouts to make the cuts. Depending on how fast and effective those strategies are, the department “will determine the need for further action to reduce staffing,” he said in prepared testimony, a reference to possible layoffs.

In back-to-back hearings Tuesday and Wednesday in which he defended the White House’s plan to slash his department’s budget by 13.4 percent, Zinke offered no additional details on whether the cuts will be concentrated in some offices or spread across Interior’s nine agencies.

But 1,000 jobs would be lost at the Bureau of Land Management — which manages hundreds of wilderness areas, two dozen national monuments and other protected lands in addition to issuing leases for livestock grazing and oil and gas extraction — according to an email its acting director sent to employees last Friday.

The contraction at Interior, which manages a fifth of all U.S. land, is one of several plans to downsize the number of employees across the government since President Trump took office. Departments from Health and Human Services to Transportation are coming up with plans to fulfill the president’s campaign pledge to reduce the size and reach of the federal bureaucracy.

Zinke’s disclosure to lawmakers comes 10 days before a June 30 deadline for all department leaders to submit initial plans showing the White House how they intend to reorganize, reduce their workforce, assess which programs are necessary and look for changes that save money.

The White House in April lifted a government-wide hiring freeze the president had imposed in January but told Cabinet secretaries they must start “taking immediate actions” to save money and reduce their staffs.

The Environmental Protection Agency plans to shed more than 1,200 employees by early September through buyouts and early retirements. Secretary Scott Pruitt has pledged to cut a total of 3,200 positions, more than 20 percent of the agency’s 15,000 employees.

A similar plan is unfolding at the State Department, where Secretary Rex Tillerson wants to lose 2,000 Foreign Service officers and other staff through attrition over the next few years, a spokesman said.

At a House budget hearing on Tuesday, Rep. Dan Newhouse (R-Wash.) pressed Energy Secretary Rick Perry on reports that the president’s proposed budget could eliminate “about 1,000 jobs” at the department’s Pacific Northwest National Laboratory in Newhouse’s district. That lab employs 4,500 people, according to the Energy Department’s website.

“I am comfortable that we will manage these labs in a way that continues to keep the employment levels at the level to deliver the innovation and technology that this country is going to need,” Perry said, stopping short of promising there would be no job losses. He said proper management could help retain more of those positions.

Perry’s predecessor as secretary, Ernest Moniz, said in an interview that he found it “rather unlikely” the proposed cuts would not lead to significant job losses unless the agency saved money by curtailing outside researchers’ access to the department’s high-end, experimental equipment.

Interior employs a total of 50,500 full-time and 20,000 part-time people, from scientists to park rangers, at its Washington headquarters and its nine departments, including the National Park Service, U.S. Fish and Wildlife Service and Bureau of Indian Affairs.

Zinke took a big first step to reorganizing the department late last week when he informed dozens of career officials there of reassignments. The shake-up appeared to be much broader than previous administrations have pursued and includes Interior’s top climate policy official, several Fish and Wildlife leaders and reassignments at the Bureau of Land Management.

In his memo to staff, BLM acting director Michael Nedd said the agency could shed 1,000 positions through “normal attrition” and would turn to buyouts and early retirement offers later this year if that number was not reached.

“While the FY 2018 budget is not final, we must heed the staffing levels that it calls for,” Nedd wrote. His email, with a subject line reading “Defining Our Priorities in a Time of Change,” was obtained by the watchdog group Public Employees for Environmental Responsibility.

PEER Executive Director Jeff Ruch called the cuts a “starvation diet.’’

“According to Trump’s fantasy plan, BLM is supposed to achieve ‘energy independence’ before its coffee break, stimulate rural ‘job creation’ by lunch and do it with substantially less resources,” Ruch said. He predicted that reductions of that magnitude would likely require layoffs.

Jane Lyder, a deputy assistant interior secretary who oversaw parks and the Fish and Wildlife Service under the Obama administration, said shrinking the number of Interior employees will create hardships, given other proposed cuts to the budget.

“Those agencies are already pretty strapped, especially the Park Service,” Lyder said. “The Park Service itself says it will curtail visitor services and might cut hours of operation to compensate.”

Interior spokeswoman Heather Swift declined to provide details on the workforce cuts or timing. “The Department has nothing further to announce about personnel right now,” she said in an email Wednesday.

Dino Grandoni and Darryl Fears contributed to this report.