A sobering study is out in Nature this week, which quantifies the benefits of marine protected areas worldwide: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13022.html. The authors found that 59% of the marine reserves were ecologically undistinguishable from non-protected areas. There is a silver lining to their findings, however: conservation benefits were greatly enhanced in protected areas that had been well-designed. In marine reserves that were large, isolated by deep water, and completely closed to fishing, the biodiversity of large fish doubled in comparison with unprotected areas. These findings emphasize that conservation isn’t simply a matter of slapping a ‘national park’ label on an ecosystem and walking away. Protected areas need to be planned carefully and monitored regularly to ensure their success.
You can read more about the study here: http://thinkprogress.org/climate/2014/02/07/3260781/marine-protected-areas-working/