Brightly colored fish swim near coral in the clear blue waters of Hawaii.
Sea of Life More than 7,000 species of marine plants and animals rely on Hawai‘i reefs—and play key roles in keeping them healthy. © Kaikea Nakachi

Stories in Hawai'i

Restoring Reefs to Build Resilience

Coral reefs are living ecosystems that protect and provide for about 25% of all marine species—and for all of us.

Underwater view of a large school of brightly colored fish swimming around a coral reef in Hawaii.
UNDERWATER BUFFET Coral reefs nourish herbivorous fish, zooplankton and filter-feeding species. © Bryce Groark

Coral reefs form the foundation of intricate food webs, providing vital nutrition and energy to a vast network of organisms.

Reefs in Hawai‘i

Closeup underwater view of pale yellow and gold coral polyps with pink tentacles off the West Maui coast.
Building Blocks Coral polyps grow together to form a colony, and colonies join together to form a reef. © Pauline Fiene

“Hānau ka ‘ukuko‘ako‘a,
hānau kāna he ‘ako‘ako‘a”

“Born was the coral polyp,
born was the coral”

Excerpt from Kumulipo

In Hawaiian culture, coral has long been revered. The sacred creation chant Kumulipo teaches us that the coral polyp was the first organism to emerge from the deep darkness, the most ancient ancestor, the foundation for all other life.

Topographic map of the Main Hawaiian Islands—from northwest to southeast Ni‘ihau, Kaua‘i, O‘ahu, Moloka‘i, Lana‘i, Kaho‘olawe, Maui, Hawai‘i—and the seafloors surrounding them.
Caring for Coasts Communities across the state help care for coastal reefs and wetlands and the wildlife they shelter and nourish. © Esri, GEBCO, Garmin, NaturalVue | Esri, TomTom, Garmin, FAO, NOAA, USGS, EPA, USFWS

Nearshore reefs and waters support more than 7,000 marine life forms in Hawai’i, 25% of which are found nowhere else in the world. In the Main Hawaiian Islands, reefs cover more than 300,000 acres—an area about the size of the island of Kaua‘i. Click through the images below to see some inhabitants of Hawaiʻi reefs.

Aerial view of Puakō, Hawai‘i, and its coastal reef.
Hawai‘i Island Kona Coast Aerial photo showing coral reef protecting homes. © C. Wiggins

These massive living structures are vital to Hawai‘i’s people, culture, lifestyle and economy, providing more than $2 billion each year in flood protection and reef-related tourism alone.

Brown sediment-filled ocean waters along a coast.
Stormy Waters Streams carry sediments from degraded uplands to coastal waters and reefs after heavy storms. © DLNR DOFAW/Jon Brito

But reefs are under increasing pressure from sediments, land-based pollutants, overfishing and climate change impacts, including rising sea levels and water temperatures, which are expected to intensify in coming years.

Corals that are bleached or covered in sediment.
Sediment Overload Excessive sediments can smother and kill coral by diminishing its ability to feed and grow. © TNC

Scientists estimate that live coral cover in at least some areas of Hawai‘i has declined by 60% over the past several decades. Reducing the impacts of local and global threats is critical to the survival of coral reefs.

Research scuba diver surveys a reef of bleached coral.
Climate Impacts TNC scientists documented a 90% loss of live coral cover in some areas following the 2015 statewide bleaching event. © David Slater

Reef restoration has been helping to regenerate reefs in other parts of the world for more than two decades. With recent bleaching events resulting in a 30% loss of live coral cover in Hawai‘i, it is essential to understand the potential of this intervention to sustain Hawaiʻi’s spectacular coral reef ecosystems and the many benefits reefs provide.

Reef Restoration

Reef restoration is the process of rebuilding or enhancing damaged or degraded coral reefs to improve their health, function and/or resilience. This can involve a variety of techniques, including coral stabilization and coral gardening. These methods aim to increase coral cover and diversity and enhance the overall resilience of the reef ecosystem.

A broken piece of brown and white coral reattached to the reef with green epoxy.
Fostering Life Collecting and reattaching corals broken by recent swells, storms and ship groundings gives them a new chance at life. © TNC/Mikayla Barnwell

Coral stabilization is the process of attaching coral fragments that have been broken off, often during damaging events like storms, large swells and ship groundings.

Broken coral fragments—referred to as “corals of opportunity”—can be replanted onto the reef using epoxy, cement or other non-toxic underwater adhesives.

Stabilizing these fragments dramatically increases their chances of survival and regrowth and prevents them from rolling around on the sea floor, where they can cause extensive reef damage.

A scuba diver monitoring the growth of rows of coral cuttings sitting on a nursery table on the sandy seafloor.
Fostering Growth Cutting and growing the broken coral in nurseries increases growth rates and helps to supply the coral needed to restore severely degraded reef areas. © TNC

Coral gardening involves growing coral fragments in land-based or in-water nurseries to generate more and/or larger coral colonies to plant back onto the reef.

The process begins with corals of opportunity that are cut into smaller fragments to generate new coral colonies and grown in nurseries to promote increased growth and survival.

Coral gardening can produce large numbers of new coral colonies quickly and efficiently.

A close-up of someone’s fingers attaching cuttings of light brown lobe coral to the reef with green epoxy.
Fostering Cohesion Cut coral pieces, planted in clusters, will fuse to form a colony. © Mikhail Rudenko/Liquid Cosmos Photo

We are also testing a newer, modified technique that involves cutting the corals of opportunity into smaller fragments and attaching them directly to the reef to fuse and form new colonies.

Prior to any reef restoration, it is essential to reduce threats on the reef that may be causing degradation and coral mortality. Improving the overall health and resilience of the reef increases the chances that planted coral will survive and thrive.

We typically reduce threats by improving conditions in the ocean and surrounding areas, for example, by promoting sustainable use of marine resources and by reducing land-based sources of pollution to improve water quality.

Learn more about these efforts.

Reef Restoration in Hawai'i

Aerial view of the fringing reef and sand channels at Olowalu, Maui.
Resilient Reefs Restoration efforts are focused on reefs that have been identified as resilient—and, therefore, best able to withstand climate impacts. © Drew Sulock

TNC’s marine scientists are working with federal, state and community partners to develop a gold-standard for science-based, adaptive and community-centric restoration in Hawai‘i. Together, we are piloting reef restoration at sites where corals have been lost but where the reefs have proven to be resilient—meaning the corals resisted or are recovering from climate-related bleaching—and where communities and government partners are implementing complementary efforts to reduce reef-damaging threats and improve reef health.

We are working in close collaboration with community partners, who selected the pilot project locations, coral species and restoration techniques that will be used in consultation with restoration scientists.

Underwater view of broken coral.
Broken Coral The partners are careful to select only corals that are already damaged and likely to die without intervention. © DLNR

We recover and use only those corals that have been broken during recent storms or high swells and would otherwise die. To minimize the risk of introducing disease or invasive species from other places, our teams only replant corals near where they were recovered.

“He pūko‘a kani ‘āina”

“A coral reef that grows into an island”

ʻŌlelo Noʻeau (Hawaiian proverb)

Pilot Sites

Pilot Sites

The Nature Conservancy worked with the National Oceanic and Atmospheric Administration, Hawai‘i Division of Aquatic Resources and University of Hawai‘i Institute of Marine Biology to develop a Coral Restoration Action Plan for the state. The plan identified priority geographic areas for restoration, and we are now collaborating with community groups and other partners to pilot reef restoration at three of these sites.

Click Points to Learn More RETURN
REEF REBIRTH (4:30) Watch video highlights of the Kanu Ko‘a launch at Ka‘ūpūlehu’s Kahuwai Bay.

Emergency Repair

Ocean waves photographed from below.
Natural Infrastructure Reefs provide flood protection for coastal communities and properties by diminishing wave energy up to 97%. © Doug Perrine

Reefs protect our shorelines by breaking down wave energy.

Hurricanes are a threat to coral reefs because they can do a lot of structural damage very quickly. Research shows that one severe hurricane can cause a 50% or more loss of live coral cover—and the loss of just one meter of reef height could double the cost of storm damage on coastal properties and infrastructure, such as roads and sewage systems.

Satellite image of hurricanes hitting Hawaii.
Insuring Nature Hawai‘i experiences 4-5 large storms each year, and these extreme weather events are expected to become more intense in the coming decades. © NOAA

TNC purchased an insurance policy covering reefs across the Main Hawaiian Islands against hurricane and tropical storm damage. Pre-determined payouts from the policy, based on windspeed in the covered area, can be made within days, providing funding to expedite essential reef repair activities such as debris removal and coral re-attachment.

We convened scientists and reef managers from government agencies, universities, local non-profits, community groups and other organizations to share restoration techniques and develop a statewide rapid response protocol. We also worked with local teams to develop response plans for each county to ensure an effective post-storm response.

Reflecting global restoration expertise and lessons learned from post-storm repair on the Mesoamerican reef, these efforts will facilitate coral regrowth after a damaging event to build reef resilience.

Monitoring Outcomes

Cover of the Hawai‘i Reef Restoration Monitoring Guide with The Nature Conservancy, Hawai‘i Division of Aquatic Resources & National Oceanic and Atmospheric Administration logos and a muted seafloor.
Reef Restoration Guide Hawai'i Reef Restoration Monitoring Guide. © TNC

Effective monitoring is vital to assess, refine and adaptively manage restoration projects. The draft Hawai‘i Reef Restoration Monitoring Guide outlines a monitoring framework based on universal metrics to ensure global comparability. The guide is being developed in collaboration with the Hawai‘i Coral Restoration Science Team to ensure it is appropriate for Hawai‘i’s unique ecological and cultural context and includes both high-tech and low-tech monitoring options to maximize inclusivity. Download a copy of the draft guide.

3D Reef Model New technologies enable TNC and partners to create three-dimensional models of reefs in order further analyze them. © TNC

Using new technologies, we are able to stitch hundreds of overlapping photos together to create 3D models of the reef. The photos can then be analyzed by computer, reducing the need for highly trained research divers.


TNC’s reef repair and restoration activities complement other actions we take to reduce local pressures on reefs and fisheries, so they are productive and abundant long in the future. Learn more about what we do.


Split view above and under water showing a coral reef underwater and mountains in the distance.
Coral Patch A coral reef is blanketed by invasive algae in the foreground with surrounding mountains, Kaneohe Bay, Oíahu, Hawai'i. © Ian Shive