What is it called when a private landowner signs a contact agreeing that their land will not be developed?

When a private landowner signs a contract agreeing that their land will not be developed, it is typically referred to as a "conservation easement." This legal agreement allows the landowner to retain ownership while ensuring that the land is preserved for specific uses, such as agriculture or wildlife habitat, and prevents future development. Conservation easements are often used to promote environmental protection and sustainable land use.