This recent article in The Scientist is sub-titled Marine protected areas reduce coral loss, but they are not enough.
I highly recommend this article for those who want to understand why coral reefs are declining. A common factor in most reef declines is loss of reef herbivores, leading to reef takeover by seaweed. This produces a negative feedback reinforcement process — a coral “death spiral” from which recovery is difficult. Evidently most of the global stresses produce this effect:
Reefs need to be managed for resilience to a host of interacting local and global stresses: The rapid losses, slow recoveries, and host of accelerating stresses make it urgent that we develop efficient strategies for intervention, based on an understanding of the ecology of coral reefs. While marine protected areas are critical to success, they alone are unlikely to allow reef survival because most are too isolated, too small, and cannot adequately leverage recovery of adjacent areas. We need to find effective ways to make damaged reefs more receptive to larval corals and thus better able to stop the death spiral that is occurring on today’s reefs. This will involve limiting the harvest of a critical mix of reef herbivores that prevent seaweeds from blooming on coral reefs. Because almost all major stresses shift reefs from corals to seaweeds, a better understanding of the processes and mechanisms underlying this shift, and its reversal, will be critical for preventing and reversing losses of coral reefs. To optimize our management efforts, we need information on the mechanisms involved in seaweed-coral interactions at all stages of the life cycle, the seaweeds that are most damaging to corals, and the mix of herbivorous fishes that consume the most damaging seaweeds. In short, we need proactive management that goes beyond establishing marine protected areas and hoping for the best.