Restoring Natural Grazing Processes Can Help Coral Reefs


Over the last few years, mass coral bleaching events have seriously impacted coral reefs in the Pacific Ocean. For example, it is estimated that the 2015 event led to the loss of around half of the coral cover from West Hawaii. Similarly, reefs in Guam were repeatedly hit by major bleaching between 2013 and 2017. Projections show that bleaching events will increase in severity and frequency. These events highlight the importance of management strategies that might prolong the survival of functional reefs and buy time to deal with climate change.

Until recently, most scientists believed that protecting herbivores was one of the most important strategies for sustaining healthy coral reefs. Reef herbivores, including parrotfish and surgeonfish, feed on algae. Some types of algae compete with corals, reducing their ability to survive, grow, and reproduce.

It seems intuitive that protecting these algae-eating herbivores would improve corals’ ability to thrive, and thus for reefs to recover from destructive events. A common management strategy to protect herbivorous and other fish is to establish a marine protected area. However, there is evidence that many MPAs have provided limited or no direct benefits to corals. Some scientists are now questioning the importance of protecting herbivores.

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