The one thing that certainly is implicit in the issue of adjaceny and isolation is the difference in wetland types that fall into these categories. Most riverine wetlands will be adjacent. The concepts of adjacency vs isolation hits at the heart of the HGM approach and that is the geomorphic position of the wetland. In order to be jurisdictional now the wetland must be positioned in the landscape such as to be associated with a tributary system which has navigable waters along its continuum. This being said, I still feel that compensatory mitigation accomplished with isolated systems should still be considered as viable in certain appropriate situations.
Mitigation is all about replacing functions.
Isolated wetlands still provide valuable functions and values to society whether or not we consider them jurisdictional. They are obviously different but many of the functions provided by isolated wetlands overlap in differing degrees with functions provided by adjacent systems. Given that the jurisdictional call is now made quite independent from the issue of whether or not wetland functions are being provided, I don't think isolated wetlands should be eliminated from consideration as compensatory mitigation. However, the need for a deed restriction or a conservation easement will have to be mandatory for any isolated wetland used as compensatory mitigation because of the lack of certainty for its future given that there will be no statutory umbrella protecting its integrity after the mitigation is released from permit liability. Obviously, by allowing compensatory mitigation to occur in these wetland subclasses and then providing protection with a conservation easement one would help stem the tide of loss for these valuable resources.