Qualified conservation contribution. Generally a charitable deduction under IRC §170 is not allowed for a donation of an interest that is less than the donor’s entire interest in the property. However, there is an exception for the value of a “qualified conservation contribution,” or the contribution of a qualified real property interest, to a qualified organization, exclusively for conservation purposes. The conservation purpose must be protected in perpetuity. 

Qualified Real Property Interest. The entire interest of the donor other than a qualified mineral interest is a qualified real property interest.

Qualified organization. A “qualified organization” is either a:

A qualified organization must have a commitment to protect the conservation purposes of the donation and have the resources to enforce the restrictions. A conservation group organized or operated primarily or substantially for one of the conservation purposes specified in section 170(h)(4)(A) will be considered to have the commitment required by the preceding sentence.  The organization, however, need not set aside funds to enforce the restrictions that are the subject of the contribution.

 

Exclusively for conservation purposes. To meet the requirements of this section, a donation must be exclusively for conservation purposes. A deduction will not be denied under this section when incidental benefit inures to the donor merely as a result of conservation restrictions limiting the uses to which the donor's property may be put.

 

Perpetual conservation restriction. A “perpetual conservation restriction” is a qualified real property interest. It is a restriction granted in perpetuity on some use that would normally be able to be made of real property- most commonly in the form of an easement.  
 

Any interest in the property retained by the donor (and the donor's successors in interest) must be subject to legally enforceable restrictions (for example, by recordation in the land records of the jurisdiction in which the property is located) that will prevent uses of the retained interest inconsistent with the conservation purposes of the donation. In the case of a contribution of a remainder interest, the contribution will not qualify if the tenants, whether they are tenants for life or a term of years, can use the property in a manner that diminishes the conservation values which are intended to be protected by the contribution.

Proceeds. For a deduction to be allowed under this section, at the time of the gift the donor must agree that the donation of the perpetual conservation restriction gives rise to a property right, immediately vested in the donee organization, with a fair market value that is at least equal to the proportionate value that the perpetual conservation restriction at the time of the gift, bears to the value of the property as a whole at that time. That proportionate value of the donee's property rights shall remain constant.
 
Accordingly, when a change in conditions give rise to the extinguishment of a perpetual conservation restriction, the donee organization, on a subsequent sale, exchange, or involuntary conversion of the subject property, must be entitled to a portion of the proceeds at least equal to that proportionate value of the perpetual conservation restriction, unless state law provides that the donor is entitled to the full proceeds from the conversion without regard to the terms of the prior perpetual conservation restriction.
 

Read the text of 26 CFR 1.170A-14