Land trusts and conservation easements are a major method by which land is taken from Americans to lock it up with the United Nations through NGOs such as the Nature Conservancy. At the heart of it is the Global Biodiversity Assessment, a document that is over 1,000 pages, but here is a summary for "policy makers". The original document doesn't seem to be available online.
Here is an article out of Maine that explains how land trusts and conservation easements are tied to Agenda 21. Take note of the reference to the Environmental Grantmakers Association, it just happens to be a UN NGO.
If you would like to see the UN's monitoring system on Idaho go to this UN site and type Idaho in the search box. Yes, they are tracking how much land that has been taken under the guise of biodiversity and how much land is left to take.