New Report Explores Science of Interventions to Save Coral Reefs

WASHINGTON – While the management of local and regional stressors threatening coral reefs is critical, these efforts on their own will not be enough in the face of global climate change, says a new interim report by the National Academies of Sciences, Engineering, and Medicine.  The committee that is conducting the study explored the state of science on a variety of approaches to sustain coral reefs in rapidly deteriorating environmental conditions and assessed the interventions' benefits and goals, feasibility, risks, and infrastructure needs.

This report is the first in a two-phase study evaluating the risks and benefits of implementing novel ecological, genetic, and environmental interventions that could enhance the recovery and persistence of coral reefs.  Around the world, coral reefs have seen major decline due to problems including climate change and widespread disease, in addition to local stress from pollution, overfishing, and habitat destruction.  Caused by above-average ocean temperatures, recent back-to-back global bleaching events – a phenomenon that results in loss of color in corals that are stressed by changing conditions –have increased coral reef losses significantly.  A major global ecosystem, coral reefs provide coastal communities with wave protection, fisheries and tourism, cultural heritage, and food and livelihoods.

“The health of coral reefs is integral to human well-being and economic development, and the recent major declines signal a dramatic loss of these values,” said Steve Palumbi, Jane and Marshall Steel Professor in Marine Sciences at Stanford University and chair of the committee.  “Consequently, scientists and reef managers see a strong need for novel approaches to prevent the loss of coral reefs, and we are also seeing exponential growth in research to test such interventions.”

The committee identified interventions at multiple ecosystem levels that could help stabilize coral reefs and maintain the many societal values of these ecosystems.  Which application used from this diverse set of approaches depends on the complex nature of coral colony, where the coral host, the symbiotic algae, and the rest of the microbiome have a role in supporting coral health and resilience.  The four categories of interventions include:

Genetic and Reproductive Interventions
These approaches provide an opportunity for increased selection and breeding of stress-tolerant traits that may improve the resilience of coral populations and species.  In addition to naturally resilient corals or members of their microbiome, genetic manipulation may provide the opportunity to create corals that can withstand increasingly severe environmental conditions.  Research into the potential for genetic manipulation of corals to improve their resilience, and its potential risk, is just beginning. 

Physiological Interventions
The committee highlighted potential treatments that could influence the physiological responses of corals without changing their genomes. Pre-exposure of corals to high temperatures has been shown to promote their ability to temporarily survive future re-exposure. Manipulation of the symbiotic algae and microbiome present opportunities for selecting communities that confer resilience.  Improvements in disease resistance and overall condition might be influenced by additions of nutritional supplements, antibiotics, and antioxidants.  Some of these interventions may have effects that remain for the lifespan of the corals, while others might be passed on to future generations.

Population and Community Interventions
Managed selection – movement of individuals from one location to another – directly seeks to alter the composition of an entire population or communities of coral reefs .  Relocation happens at different scales: assisted gene flow supports the expansion of resilient species or genotypes in their range, assisted migration  supports the movement of corals to areas just outside their range, and introduction to new areas supports movement of coral to new ranges including across ocean basins.

Environmental Interventions
Strategies that employ a portfolio of local coordinated interventions to reduce light and heat stress include local cooling and shading. Reduction of ocean acidification in combination with biological and ecological interventions may also be necessary to ensure the persistence of coral reefs.

The report notes that these interventions have not been implemented beyond experimental scales in the field, which makes their efficacy and impacts uncertain at this time.  In its final report, the committee will provide an environmental risk assessment and decision framework for evaluating the risks and benefits of implementing these interventions. Although reducing carbon emissions is an important mitigation strategy for addressing the impacts of climate change, even limiting human-induced surface warming to 2 degrees Celsius is unlikely to save most coral reefs from the increased frequency and severity of bleaching events without further interventions, the report says. 

DETAILS: A Research Review of Interventions to Increase the Resilience of Coral Reefs – Interim Report is available for immediate release.  Media inquiries should be directed to the National Academies' Office of News and Public Information; tel. 202-334-2138 or e-mail news@nas.edu.