If Congress doesn’t agree on a short-term spending bill to maintain funding for the federal government by September 30, a shutdown may be on the horizon. And if the U.S. government indeed shuts down, many former national park employees think national parks should, too.

Dozens of former national park superintendents and the Coalition to Protect America’s National Parks (CPANP) urged Interior Secretary Doug Burgum in an open letter to “protect our parks and public lands by closing them if a government shutdown occurs.”

“As former superintendents of national parks across the country, we write to you with an urgent appeal to protect our parks and public lands by closing them if a government shutdown occurs,” the group wrote in the September 25 letter. “Past shutdowns in which gates remained open with limited staff have hurt our parks: iconic symbols cut down and vandalized, trash piled up, habitats destroyed, and visitor safety jeopardized. If you don’t act now, history is not just doomed to repeat itself, the damage could in fact be much worse.”

Congress determines the National Park Service (NPS) annual budget because the bureau is housed within the Department of the Interior. When Congress fails to pass a budget, shutdowns may occur. During federal closures, government programs and sites considered non-essential to national security or safety—such as those run by the NPS—are at risk of losing both funding and employees.

The federal government has experienced at least 14 shutdowns since 1980, according to the Bipartisan Policy Center, a nonprofit think tank. But the government has only shut down twice in the 21st century. The first occurred in 2013, when over 400 national park locations closed. The most recent shutdown, which took place in December 2018, is also the longest in U.S. history, lasting for over 34 days.

In the past, these shutdowns “have hurt our parks,” wrote CPANP in the latter. The advocacy group comprises 4,600 current, former, and retired NPS employees and volunteers.

During the 2018 shutdown, some 80 percent of Park Service employees were furloughed; however, many of the country’s most iconic parks remained open, managed by a bare-bones crew. At the time, Outside reported that there was no one to collect park fees, guide tourists, plow the roads, or clean overflowing pit toilets. Trash was being cleared only by a few volunteer groups in a handful of popular sites.

In advance of a possible shutdown in the fall of 2023, some state governors, including Katie Hobbs of Arizona and Utah’s Spencer Cox, announced they would use state funds to keep national parks open. The 2023 shutdown was averted, however, and it remains unclear whether similar state-led initiatives will keep parks funded and open in a possible 2025 shutdown.

According to the CPANP, keeping national parks open during a government shutdown, particularly in the current context, could lead to worse outcomes than in the past. National parks are already under pressure to remain open amid severe workforce reductions, due to a swathe of budget cuts implemented by the Trump Administration in the spring.

“Sure, we can keep everything open,” an anonymous NPS ranger told Outside in April after a round of cuts earlier this year. “But who wants to recreate in a park with broken down facilities and no maintenance and no search and rescue?”

The CPANP says any attempt to keep parks running during the shutdown would be courting disaster.

“If national parks are to be open to visitors when National Park employees are furloughed, these nascent issues from the summer season are sure to erupt,” the CPANP letter states. “Leaving parks even partially open to the public during a shutdown with minimal—or no—park staffing is reckless and puts both visitors and park resources at risk.”