Purchasing land or securing development rights is a very good idea when there is a clear and iminent threat to losing the habitat value it provides. Conversion of forestland to a housing development, for example. Purchase of riparian corridors along mainstem rivers already protected by Forest Practices regulations and state shoreline rules, maybe some benefit there. Buying up forestland "in the watershed even if fish can't access it" would be a pretty low priority for expenditire of scarce restoration dollars.