I wasn't part of the California experience and I haven't followed what happened there. I'm sure in the research the committee has done you've heard about programs like Marxan, which allow you to plan. Programs like that allow you to find the optimal compromise between protection of areas that have lots of biodiversity and areas that are used a lot by various groups. It is possible to close areas that optimally fulfill the goals of protecting biodiversity while minimizing conflict with users.
In respect of MPAs, we're not talking about closing all the best areas. There has to be protection and some access to good areas, and at the end of the day it is a compromise.