An easement is a limited right, granted by the owner of real property, to use all or part of his property for specific purposes. A traditional legal use of an easement, for example, has been for owner A, on whose property a stream flows, to allow neighbor B to cross A's property in order to take water from A's stream.

Within the last century, this common-law device has been adapted to a modern purpose: natural resources conservation. Easements for conservation purposes touch a different set of rights—the property owner's right to develop, improve, or modify his property, and the buildings on it, generally as he sees fit. An easement for conservation or preservation purposes involves the relinquishment of some of these rights (i.e., the right to alter or diminish a building or to cut down a forest) and the power in the new holder of the easement to enforce the restrictions on the use of the property.