One measure of the decline is the airline industry in Washington, where travel representatives report a steep falloff in the number of people flying on discounted government rates. Intercity bus services like Megabus have meanwhile seen a jump in ridership between Washington and New York.

The impact goes far beyond the elimination of embarrassing junkets like the more than $800,000 the General Services Administration spent on a clown, a comic, a mind reader and airfare for 300 government workers for a retreat near Las Vegas in 2010. Officials have urged agencies to cut travel budgets “in a way that protects mission to the extent practicable and continues to support critical government functions such as national security, safety inspections, and law enforcement,” said Steve Posner, the associate director for strategic planning and communications at the Office of Management and Budget.

But Mr. Posner added: “The depth and breadth of the cuts required by sequestration mean that is not possible in all cases, and cuts are having an impact on agencies’ ability to carry out their mission.”

A July report by the United States Travel Association, made up of companies in the travel industry, found that government participation in meetings and conferences was vital to making it efficient and effective. The report found that canceling participation in these events carried significant costs and undermined important functions of government.

Among those hit hardest by the cuts to travel budgets are scientists, who often travel to academic conferences as part of their jobs. In some cases, they are now turning to video conference calls or online Webinars to replace the in-person visits.

In February, the Defense Department canceled a health systems conference where thousands of military medical professionals would gather to share research and learn the latest treatment techniques.

In March, the National Space Symposium went on as scheduled — just without NASA. The agency has also canceled one trip abroad by Charles F. Bolden Jr., the administrator.