Should national parks, forests be opened to private use?

The mountains, meadows, woods, and canyons labeled national parks and national forests are protected from onrushing civilization by the strong arm of the United States government.

But should those lands be inviolate? When might Washington's protective arm be withdrawn? These questions are raised by current administration-backed attempts to downgrade certain national recreational lands.

The US Department of Agriculture (USDA), as part of President Reagan's plan to dispose of excess public land, is studying 6 million acres of national forest for possible sale.

A bill with some powerful supporters, now being considered in Congress, would roll back the national-park designation for much of Alaska's federal parkland, so sport hunters could regain access to some of their prime stalking grounds.

The federal government has never treated all national wild-land designations as irrevocable. The USDA has traditionally swapped less-needed bits of national forest with private landowners to consolidate and improve government holdings. The national forest now being studied for its commercial possibilities, says the USDA, is that sort of land: ''isolated parcels, some lands in checkerboard ownership patterns, lands needed for community expansion, and some lands'' leased to private owners for summer homes, according to a USDA report.

The 6.3 million acres involved represent about 3 percent of the national forest system. The impact varies widely between states, however: Less than 1 percent of the federal forest in Idaho is being studied for possible sale, while 36 percent of Ohio's is undergoing such scrutiny.

Of course, stresses the USDA report, the fact that the study is being undertaken ''does not mean all those acres will be sold.'' And even environmentalists admit there are extraneous bits of national forest that might just as well be peddled to the private sector.

But the sweeping nature of the government's inquiry, say environmentalists, troubles them.

''The acreage the government (has singled out for study) adds up to more than scattered parcels and summer cottages,'' says Debbie Sease, a public lands expert with the Sierra Club.

Lands being studied for sale include the entire Holly Springs and Tombigbee National Forests in Mississippi. Ninety percent of North Carolina's Uwharrie National Forest is under scrutiny.

''Uwharrie is the only substantial block of public land in central North Carolina,'' says James Dockery, the state's Sierra Club chairman. ''It would be outrageous to dispose of any of it.''

Ultimately, any White House proposal to sell national forest land would have to clear Congress. Such a bill would likely find tough going on Capitol Hill - particularly in the House interior subcommittee on public lands, chaired by environmentally minded Rep. John Seiberling (D) of Ohio.

''I wonder if they'll even get around to sending a proposal up here,'' says a subcommittee aide.

By comparison, the bill to allow hunting in Alaska's national parks is moving along at a smart clip. Introduced by Alaska's congressional delegation, the legislation was the subject of an April 15 Senate hearing.

Cosponsored by Senate majority leader Howard Baker (R) of Tennessee and Energy and Senate Natural Resources Committee chairman James McClure (R) of Idaho, the bill will get serious attention, at least in the Republican-dominated Senate. The bill would downgrade the status of 12 million acres of Alaskan national park from national park to national preserve - opening the area to sport hunting.

The 1980 Alaska National Interest Lands Conservation Act, which established 24 million acres of national park in Alaska, substantially reduced sport-hunting opportunities in the state, complains an aide to Sen. Ted Stevens (R) of Alaska. Subsistence hunting by natives is allowed on much of the state's national parkland. Allowing sport hunting by outsiders is thus a matter of equity, says this aide.

Environmental groups, claiming that 92 percent of Alaska is already open to sport hunting, say passage of the bill would set dangerous precedents - both for allowing hunting in national parks, and for reopening the 1980 Alaska Lands Act.

''There's just no need for this bill. Its major beneficiaries are a group of hunting guides and rich hunters,'' says Destry Jarvis, a director of the National Parks and Conservation Association.