About Easements

Conservation Easements
The most traditional tool for conserving private land, a "conservation
easement" (also known as a conservation restriction) is a legal agreement
between a landowner and a land trust or government agency that
permanently limits uses of the land in order to protect its conservation
values. It allows landowners to continue to own and use their land, and
they can also sell it or pass it on to heirs.

When you donate a conservation easement to a land trust, you give up
some of the rights associated with the land. For example, you might give
up the right to build additional structures, while retaining the right to grow
crops. Future owners also will be bound by the easement's terms. The land
trust is responsible for making sure the easement's terms are followed.
This is managed through "stewardship" by the land trust.
Conservation easements offer great flexibility. An easement on property
containing rare wildlife habitat might prohibit any development, for
example, while an easement on a farm might allow continued farming and
the addition of agricultural structures. An easement may apply to all or a
portion of the property, and need not require public access.

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Qualifying For A Tax Deduction
A landowner sometimes sells a conservation easement, but usually
easements are donated to a land trust. If the donation benefits the public
by permanently protecting important conservation resources, and meets
other federal tax code requirements, it can qualify as a tax-deductible
charitable donation. Easement values vary greatly; in general, the highest
easement values result from very restrictive conservation easements on
tracts of developable open space under intense development pressure. In
some jurisdictions, placing an easement on your property may also result in
property tax savings.

Reducing Estate Taxes
Perhaps the most important benefit, a conservation easement can be
essential for passing undeveloped land on to the next generation. By
removing the land's development potential, the easement typically lowers
the property's market value, which in turn lowers potential estate tax.
Whether the easement is donated during life or by will, it can make a
critical difference in one's heirs' ability to keep the land intact.

Source: Land Trust Alliance

http://www.landtrustalliance.org/what-you-can-do/conserve-your-land/benefits-landowners