The National Geographic Society on Tuesday announced it is laying off about 9 percent of its staff. (Bill O'Leary/The Washington Post)

The National Geographic Society of Washington will lay off about 180 of its 2,000 employees in a cost-cutting move that follows the sale of its famous magazine and other assets to a company controlled by Rupert Murdoch.

The reduction, the largest in the organization’s 127-year history, appears to affect almost every department of the nonprofit organization, including the magazine, which the society has published since just after its founding in 1888. The reduction also will affect people who work for the National Geographic Channel, the most profitable part of the organization. Several people in the channel’s fact-checking department, for example, were terminated on Tuesday, employees said.

The National Geographic Society said “involuntary separations” will represent about 9 percent of its workforce. In addition, buyout offers have been made to an undetermined number of employees.

In September, the organization sold the magazine and its stake in the National Geographic cable TV channel, as well as other media properties, for $725 million to a for-profit partnership controlled by 21st Century Fox. The society will have a 27 percent stake in the partnership, called National Geographic Partners; Fox — a company controlled by Murdoch and his family — will own the balance.

The deal, which will close in mid-November, precipitated concerns about layoffs at the organization, which has generally avoided wide layoffs despite the long decline of its flagship magazine. Some employees began referring to October as “Choptober” and to November as “Knivember.”

In a staffwide e-mail Monday, Gary Knell, the society’s chief executive, wrote that a restructuring plan would be announced Tuesday. He added ominously, “Please watch your inbox for important information about your employment status tomorrow.”

Knell also wrote: “I cannot thank you enough for your patience and hard work over the last few months. I am proud of how our teams and our organization have approached and responded to this transitional period. Looking ahead, I am confident National Geographic’s mission will be fulfilled in powerful, new and impactful ways, as we continue to change the world through science, exploration, education and storytelling.”

A spokeswoman for National Geographic said the decision to undertake the layoffs was not part of the September deal with Murdoch. “We wanted to take care of our long-serving employees,” M.J. Jacobsen said.

In addition to the layoffs and buyouts, the National Geographic Society said it would freeze its pension plan for eligible employees, eliminate medical coverage for future retirees and change its contributions to an employee 401(k) plan so that all employees receive the same percentage contribution.