An important tool in conserving Hill Country land is a land preservation agreement, also known as a conservation easement. A land preservation agreement is a recorded written agreement between a landowner and a nonprofit land trust in which the landowner freely places a limit or restriction on his property in order to protect it.

Click here for the Hill Country Conservancy Resources.

The first conservation easement on the Annandale, covering 3,058 acres, was purchased in 1999 by the Nature Conservancy of Texas in collaboration with the Edwards Aquifer Authority and San Antonio Water System (SAWS). In 2001, a second easement was completed on 998 acres, this time donated by the family. These first two easements primarily targeted the Frio Bat Cave to protect the maternity colony of Mexican Freetail Bats on the adjacent property.

Since the third easement on the Annandale was the largest and consisted of the riparian areas on the ranch, careful measures were taken to precisely define the Non Development Zones (NDZ) protected under the document. In addition to buffering the known cave and recharge features, the NDZs included floodplains and water quality stream buffers to further enhance protection of water quality and potential recharge. In 2007, the acquisition of the easement was at long last finalized, made possible by SAWS Project Fund and a federal grant from the Environmental Protection Agency. It included 7,552.68 acres, bringing the total protected acreage of the ranch to about 11,600.