right-libertarians don't believe in a commons, though. they believe that the commons should be converted into private property. they'll argue that rivers and lakes and even sections of the air should be sold off, that nothing at all should be under common ownership. in fact, that's the most common answer you hear from them to the global warming issue: property rights. in their minds, if you sold all the green spaces off to private owners then those private owners would ensure the land is taken care of. if you sold the air off to private investors, they would keep it clean to maximize their investment. and, then they can sue each other over rights-infringements whenever somebody pollutes their air.