McLaughlin talks about conservation easements and the doctrine of merger. This article explains that merger generally should not occur in such cases because the unity of ownership that is required for the doctrine to apply typically will not be present. For merger to occur, the two estates must be in the same person at the same time and in the same right.
Nancy A. McLaughlin,
Conservation Easements and the Doctrine Of Merger,
74 Law and Contemporary Problems
Available at: http://scholarship.law.duke.edu/lcp/vol74/iss4/12