FLAGSTAFF, Ariz. (AP) — Visitation to national parks, monuments and other sites managed by the National Park Service increased in 2016, but the parks' popularity has led to $11.9 billion in deferred maintenance needs.

Last year, 330 million people visited NPS sites nationwide — 7 percent more visitors than in 2015, The Arizona Daily Sun (http://bit.ly/2oNAT4n ) reported last week.

But conservation groups worry that the park maintenance backlog — $371 million at Grand Canyon National Park alone — could be used as an argument to increase privatization of national parks and as a reason to defund other Interior Department programs.

President Donald Trump's latest budget proposal includes a 12 percent cut to the Department of the Interior, which manages the parks.

The spending plan justifies eliminating $120 million used to fund federal lands acquisition by saying the money will instead go toward \"investing in, and maintaining, existing national parks, refuges and public lands.\"

The Property and Environment Research Center, a conservative think tank, cited the deferred maintenance bills as a reason to consider a franchise idea where nonprofits, individuals or businesses would own and operate land under the National Park Service brand.

The left-leaning Center for American Progress and the nonpartisan Center for Western Priorities, however, say the nearly $12 billion backlog is not what it seems.

The groups said the 2015 data shows that $389 million of the agency's deferred maintenance is supposed to be performed by concessionaires, and another $5.9 billion is needed for paved roads projects that should come from transportation funding bills.

The Center for American Progress said in a recent report that critical projects that are the direct responsibility of the Park Service total only $1.3 billion.

\"A more modest commitment of funding could go a long way toward maintaining the health and well-being of the nation's parks and all who enjoy them,\" the report said.