A grant, not a dispute
A conservation easement is procedurally unlike every dispute doctrine on this site. The owner voluntarily conveys a recorded, usually-perpetual restriction to a qualified holder — a land trust or government agency — giving up certain development rights to protect agricultural, scenic, habitat, or historic value.
The IRC §170(h) requirements
A donated conservation easement may qualify for a federal charitable deduction under Internal Revenue Code section 170(h), but the requirements are strict: a qualified organization must hold it, it must serve a qualified conservation purpose, and the purpose must be protected in perpetuity. These elements are heavily litigated — the perpetuity and conservation-purpose requirements in particular — so a tax advisor and a real-property attorney should be involved before you rely on the deduction.
Common pitfalls
Defective perpetuity clauses, unqualified holders, and overvalued appraisals are the classic ways a conservation-easement deduction is disallowed. The conservation purpose must be genuine and enforceable, and the appraisal must be defensible.