Land can also be donated by land owners, and given to trusts in people's wills. If you want to protect land you own, but not lose ownership, you can contact conservation organizations, and come up with a contract that works for your own needs for example promising not to build, graze animals, or hunt in return for tax breaks. You can pick any combination of restrictions that works for you, your family, and the organization who's job it becomes to come monitor each year. Generally once a year to fill out paper work and take photos to prove that the land really is being kept in accordance with the protective rules.

I could be wrong (I should brush up on my reading), but I think if a neighbor tried to put an illegal sewage outlet pipe that empties into your land, dumps rubbish, or removes trees along the boarder that should be protected, that the conservation organization would be able to help by lending legal strength against the people committing those criminal acts on protected land. Their photos, notes, and maps of the area could be used to help provide evidence in a legal court, so anyone with asshole neighbors might be able to benefit from the added legal status for their land.