Salazar’s words of caution come as the National Park Service released a report Monday that showed 398 national parks pumped $30.1 billion into the economy and provided 252,000 jobs in 2011.
The looming sequester has forced Interior to put a hold on hiring seasonal summer staff, Salazar said. Contracts for parks that require some preparatory work for the busy season that begins in March — such as plowing roads — are also frozen.
As a result, some facilities and services could close at parks across the country. Safety personnel also would likely diminish, pushing parks to curtail use of some hiking trails and campgrounds.
Salazar said "thousands" of permanent staff would be furloughed. But because those employees would get a 30-day notice of such action, lawmakers would have until at least April 1 to avoid that scenario.
Whether Congress can strike a deal to offset the sequester by Friday's deadline remains unclear.
Democrats and President Obama want to use a combination of tax increases and spending cuts to replace the automatic measure. Republicans want to arrive at a solution solely through spending reductions.
Obama has asked Congress to pass a stopgap agreement if the two sides cannot strike a bargain by Friday.