Payments to landowners are a major vehicle to assure resource conservation and environmental protection. Examples of payment programs are listed in the sidebar, page. 34. Some of these programs (1, 2 and 3) compensate resource owners for changing resource uses while others (4, 5 and 6) involve the outright purchase of a resource. For example, the Conservation Reserve Program (CRP) has compensated landowners to retire 37 million acres of highly erodible cropland at a current annual cost of approximately $1.9 billion, and the Nature Conservancy has protected more than 11 million acres of environmentally valuable land in the United States through purchase of donation.