It is hard to envisage a no-entry sign tagged to a towering redwood tree. But the recession – writ on an epic scale in California's proposal to close 220 state parks – is forcing the American public to confront the closure of the great outdoors.

Arnold Schwarzenegger, California's governor, is trying to make up a $26bn (£16bn) budget shortfall, and has suggested that California can no longer afford to run its parks.

Conservationists are meanwhile arguing that California cannot afford not to. And this week the federal government appeared to partly agree, with the National Parks Service threatening to seize some of the sites if Schwarzenegger goes ahead with the closures.

The proposed shutdown of the parks would affect 80% of California's nature reserves, historic sites and recreation areas, and restrict access to 30% of the state's coastline. Affected areas would stretch from the mountains of the Sierra Nevadas to the beaches and wetlands of Big Sur, and to the deserts of San Diego, where some of the last peninsular bighorn sheep roam.

California is not alone. The crisis has also exposed hitherto hidden casualties of the economic downturn, with states from Oregon to Illinois, and New York to Tennessee, struggling to stretch resources.

Other states have proposed budgets that would put closed signs on parks and historic sites, though none so far has adopted measures as extreme as those being put forward in California.