If a taxpayer contributes a conservation easement in land to a qualified organization, to obtain an income tax deduction the contribution must be in perpetuity. However, the law recognizes that sometimes the easement must be unwound (for example, if the land is taken by the government under eminent domain). In that case, a portion of the value of the property must be given to the qualified organization for conservation purposes.

As to how much the qualified organization must receive, Treas. Regs. § 1.170A-14 (g)(6)(ii) says . . .