Mass Coral Bleaching Expected With Status Quo Carbon Emissions – Can Climate Adaptation Provide Any Hope?

By Rachel M. Gregg
Palmyra Atoll National Wildlife Refuge/U.S. Fish & Wildlife Service

Coral reef ecosystems provide important services; they are sources of food, habitat, biodiversity, and coastal protection, and are economically valuable. Corals are extremely vulnerable to climatic changes; a 1°C temperature change has been known to cause bleaching (Global Coral Reef Alliance). Bleaching occurs when corals, stressed by temperature changes, expel the zooxanthellae living inside their tissues, causing the corals to turn white.  

Under status quo carbon emissions, approximately 75% of coral reefs worldwide will experience annual bleaching events by 2045, according to a study published in a recent issue of Nature Climate Change (van Hooidonk et al. 2013). The study, funded by the Pacific Islands Climate Change Cooperative, examines the relationship between emissions scenarios and the spatial variability of climate-induced effects on coral reefs. The study concludes that equatorial reefs are likely to experience annual bleaching the soonest; reefs identified as temporary refugia from increased water temperatures include those in the western Indian Ocean, French Polynesia, and the southern part of the Great Barrier Reef in Australia. Reducing carbon emissions would likely delay bleaching events by more than 20 years. Without a major global policy shift to address carbon emissions, however, bleaching events will become more persistent. In addition, corals are at risk from ocean acidification and non-climate stressors, such as habitat degradation, pollution, and overfishing.

So what can be done in the interim with regards to climate change adaptation?
  • Include coral species in threatened and endangered species designations. Elkhorn (Acropora palmata) and staghorn (Acropora cervicornis) corals were designated as “threatened” under the U.S. Endangered Species Act in 2006. NOAA Fisheries recently proposed the reclassification of elkhorn and staghorn corals as “endangered,” as well as the listing of an additional 66 species in the Pacific and Atlantic/Caribbean under the Endangered Species Act. This would prohibit the take, harming, wounding, killing, and collection of these species. The public comment period on this proposal has been extended to April 6, 2013.
  • Engage in coral restoration. In the Florida Keys, the Coral Restoration Foundation has successfully created offshore staghorn nurseries and restored damaged reef areas.
  • Create targeted coral research programs. The Coral Reef Ecosystem Studies (CREST) project investigates the health and resilience of corals to future ecosystem changes in order to guide management decisions in the Dry Tortugas, Virgin Islands, and Biscayne National Parks, and selected areas of the Florida Keys National Marine Sanctuary.
  • Create refugia and protected areas. The Nature Conservancy assisted with the creation of a climate-resilient marine protected area network in Kimbe Bay, Papua New Guinea. The scientific design of the network protects resilient corals and supports larval connectivity between  protected areas to facilitate recovery from bleaching events and other disturbances.
  • Increase monitoring and rapid assessment programs. Early detection of bleaching events and other disturbances is key to recovery and restoration. Example programs and resources include the Global Coral Reef Monitoring Network, Great Barrier Reef Marine Park Authority BleachWatch, NOAA Coral Reef Watch, and A Global Protocol for Assessment and Monitoring of Coral Bleaching.
  • Incorporate climate-smart strategies into coastal and marine spatial planning for coral reefs. Coastal and marine spatial planning (CMSP) allows for the management of uses and activities at local and regional scales; including climate change in these efforts can increase the resilience of plans and policies over the long term.
    • The Climate Change Action Plan for the Florida Reef Tract (2010-2015) outlines several actions to protect reefs in the region; among the priorities listed are several related to CMSP, including:
      • Developing and implementing a zoning plan in order to provide protection from non-climate stressors for representative habitats in the Florida Reef Tract;
      • Increasing resilience by decreasing negative user impacts of fishing, diving, and other reef uses to protect habitat and key functional groups of plants and animals;
      • Partnering with key stakeholder groups (e.g., diving, fishing, tourism industries) and providing training opportunities to increase understanding of climatic impacts; and 
      • Mapping areas of high and low resilience to prioritize management efforts (e.g., identifying and protecting refugia for thermally-tolerant coral species).
    • Strategies included in the Great Barrier Reef Climate Change Action Plan that are or could be aimed towards incorporating climate change into the Great Barrier Reef Zoning Plan include mapping areas of high and low resilience to prioritize management effort, identifying and protecting transitional habitats and connectivity, protecting the most vulnerable species and habitats from non-climate stressors. More information on these efforts may be found in EcoAdapt’s Climate-Smart CMSP Case Study #1: Great Barrier Reef. Additional climate-smart CMSP case studies are available on efforts in the Baltic Sea and England and Wales.

To view other case studies and resources related to climate change adaptation strategies for coral reefs, please visit the Climate Adaptation Knowledge Exchange (CAKE).