A new study shows that popular restoration efforts would need to be conducted at much greater spatial and temporal scales than currently pursued in order to have long-term benefits.
OAKLAND, CA – May 11, 2022 – A new study this week shows that a popular coral restoration technique is unlikely to protect coral reefs from climate change, and is based on the assumption that local threats to reefs are managed effectively. The research, published in the journal Ecological Applications, used innovative models to explore the response of coral reefs to restoration projects that propagate corals and outplant them into the wild. Additionally, the study evaluated the effects of outplanting corals genetically adapted to warmer temperatures, sometimes called ‘super corals,’ to reefs experiencing climate change as a way to build resilience to warming.
The models found that neither approach was successful at preventing a decline in coral coverage in the next several hundred years due to climate change, and that selectively breeding corals to be more heat tolerant will only lead to benefits if conducted at a very large scale over the course of centuries. Even then, benefits won’t be realized for 200 years. Restoring areas with corals that haven’t been selected to be more heat tolerant was ineffective at helping corals survive climate change except at the largest supplementation levels explored.
“The scenarios where coral reefs showed the greatest resilience to climate change were those where natural genetic variance was highest, and outplanting heat-tolerant corals in those areas had little to no effect on outcomes,” says Dr. Lukas DeFilippo, who co-led this research as a graduate student and postdoctoral scholar at the University of Washington, and is now a research scientist at the National Oceanic and Atmospheric Administration.
“Our previous research shows that corals have the best chance of adapting to the effects of climate change, like warming ocean temperatures, if there is high genetic diversity and if habitat is protected from other local stressors.” says Dr. Lisa McManus, the other co-lead, who conducted this work as a postdoctoral researcher at Rutgers University and is now faculty at the Hawai‘i Institute of Marine Biology. “Repopulating a coral reef with corals that have similar genetic makeups could reduce an area’s natural genetic diversity, and therefore make it harder for all corals to adapt to climate change.”
Coral reef restoration techniques are widely applied throughout the world as a way to repopulate degraded coral reef areas. Though the practice has some benefits, like engaging and educating communities about reef ecosystems, or replenishing a coral reef population after an area has been hit by a storm or suffered direct physical damage, more scientists are speaking up about the limitations of conservation approaches that focus solely on restoration.
“There’s a time and place for coral restoration, but ultimately, restoration alone likely won’t save coral reefs from warming waters for the foreseeable future,” says Dr. Helen Fox, one of the co-authors on this study and the conservation science director at the Coral Reef Alliance. Fox’s doctoral research focused on coral restoration and she is one of few early researchers to have studied its cost effectiveness and long-term success rate. “For starters, if we don’t also address local threats to reefs, like poor water quality and overfishing, then any corals that are outplanted may also eventually die.”
The paper’s authors agree that focusing solely on coral restoration and genetically engineering corals to be more tolerant of high temperatures is risky. Our understanding of the genes that determine heat resistance is limited, and focusing on reproducing just one single trait could undermine a coral’s resilience to other stressors or its natural ability to adapt.
Restoration practices also carry a hefty price tag and require a lot of resources. The median cost of restoring just one hectare (or about 2.5 acres) of coral reef has been estimated at over $350,000, and that’s not factoring in the high mortality rates that often come with such projects and the cost of genetically modifying corals.
“My biggest takeaway from this study is that the scale at which restoration would need to be done is so large that we instead give corals a better chance of surviving climate change with reef management strategies that focus on promoting natural genetic variance,” says Dr. Madhavi Colton, another co-author on the paper and the executive director of the Coral Reef Alliance. “This means keeping corals healthy by creating and managing marine protected area networks, reducing pollution through better wastewater treatment, and reducing greenhouse gas emissions.”
This study was the result of a collaborative effort between the Coral Reef Alliance, University of Washington, Rutgers University, Stanford University, University of Queensland, University of Hawai’i, and The Nature Conservancy; funded by the Gordon and Betty Moore Foundation and The Nature Conservancy.
ABOUT THE CORAL REEF ALLIANCE
The Coral Reef Alliance (CORAL) is committed to saving the world’s coral reefs. The nonprofit organization works at local, regional and global levels to keep coral reefs healthy so they can adapt to climate change and survive for generations to come. As one of the largest global NGOs focused exclusively on protecting coral reefs, CORAL has used cutting-edge science and community engagement for nearly 30 years to reduce direct threats to reefs and to promote scalable and effective solutions for their protection. Learn more about their approach at coral.org.