Public Parks and Government Owning the Land

A lot of libertarians, at least as far as I've encountered, seem to think the government should have public parks or forests, or that these public parks and forests are outside the realm of what government should be involved in. However, as Sam points out with his idea of how government should possibly run - the government owns all the land and people sort of rent/buy the rights to its use - and as Ian points out with his idea - the government's job is to protect natural resources and perpetrate people who violate other people's property and who pollute, and thus in order to be able to distribute rights to these natural resources, the government must, in some sense, own them. So it seems to me that most people agree that government owns the land and it is the government's job to protect the land. So then why shouldn't the government have public parks and forests? I'm talking National Parks here - like Yosemite, Old Faithful Geyser in Yellowstone, the Sierra Nevada, etc - are important National Resources, ecologically, aesthetically, etc. While National Forests, the government keeps in the public domain but won't sell or lease the land to the public, but will sell rights to companies to log, ranch, mine the land, etc. Should the government create National Parks? Do they have a right to? Or should this be part of the private sector? And if it should be part of the private sector, should this be because the private sector would be more efficient, or the government just really shouldn't be in this business at all.