Benefit to water quality, fish, and wildlife would be the difference between current management and whatever the new management scheme would be. You are not talking about going from no protection to 100% protection. Public lands already have some very restrictive regulations that are intended to maintain productive habitat. Incremental benefit there may be only slight or even negative for some things. IMO this seems to be more about aesthetics or expanding the park, with the fish and wildlife card thrown in to garner broader support.