Five reasons why our coral reefs have hope

We explore five cutting-edge developments that could help restore and maintain reefs.

A diver explores the complex and beautiful seascape of a restored coral reef.
Photograph courtesy of the SHEBA® brand

Coral reefs are some of the most beautiful and biodiverse ecosystems on the planet, covering less than one percent of the ocean floor, but containing a quarter of all marine life. However, all is not well in this underwater paradise. In the last 20 years, around half of all coral reefs have died, and the remainder are threatened by pollution, overfishing, and climate change. It’s increasingly recognized that the best way to ensure the future of coral reefs is to work to reverse climate change, protect the ocean, and actively restore reefs that cannot recover on their own. Here are five innovative ways that the world’s colorful coral reefs are being restored and given hope.

LarvalBot: The Shepherd of the Seas

Despite their plant-like appearance, corals are animals that mostly reproduce by spawning, releasing tiny eggs and sperm into the water that become coral larvae. Mass spawning events can produce billions of larvae, but where coral cover and health are poor, nature needs a helping hand. This is where the LarvalBot comes in. Developed at Australia’s Queensland University of Technology, LarvalBot is an autonomous underwater drone that shepherds coral larvae to where they can do the most good on the Great Barrier Reef. Eggs and sperm are gathered into floating enclosures where they develop and grow in a safe environment. When ready, around 100,000 microscopic coral larvae are carried by the LarvalBot to damaged areas of reef, where they are gently released to settle, grow, and repopulate sites that nature alone might not restore. The LarvalBot uses cameras to navigate its way around the reef as it efficiently delivers larvae to carefully targeted locations. And its talents extend to underwater surveys, testing water quality, and removing pests—as well as monitoring the growth of the colonies it has sown.

Reef Stars: From Rubble Beds to Healthy Reefs 

Some 30 years ago, fishermen off the coast of Sulawesi in Indonesia threw homemade explosives into the sea in a destructive practice called blast fishing. This also reduced the coral reef to a vast artificial rubble bed and permanently destroyed the ecosystem: the reef could not recover on its own because coral larvae could not safely attach to the constantly shifting debris left behind. Now, the Mars Assisted Reef Restoration System (MARRS) is transforming these rubble beds into thriving reefs―as can be seen at the appropriately named Sheba Hope Reef . At the heart of the project are specially designed “reef stars.” These three-foot-wide, star-shaped steel structures coated with sand and tied with coral fragments are embedded into the rubble field and connected together to form a stable platform on which coral can grow. The reef stars are made locally and can be laid very quickly: a team of divers can place reef stars across an area the size of a tennis court in a day, deploying over 5,000 coral fragments in the process. In just over 18 months, Sheba Hope Reef has blossomed from less than five percent coral cover to more than 55 percent, and large numbers of fish have already returned to repopulate the once devastated area.

Coral Gardening: Giving Coral the Chance to Grow

With positive human intervention increasingly important for the survival and restoration of coral reefs, a steady supply of healthy coral is essential. To overcome some of nature’s uncertainties, coral gardening was developed to allow coral to grow in a safe, threat-free environment. Also called coral nurseries or coral farms, coral gardens utilize small fragments of coral collected from damaged reefs or sustainably harvested from healthy reefs by attaching them to underwater structures in protected areas of the sea or even in land-based facilities. Over six to 12 months, the coral fragments grow to maturity and are used to propagate new corals that can be transplanted to repopulate damaged or even dead reefs. Coral gardening allows thousands of corals to be grown from a relatively small stock without damaging healthy corals in the wild. There has also been a focus on breeding corals that have naturally survived environmental stresses, such as the heatwaves that cause bleaching events. These so called “super corals” may have a genetic advantage that could help replanted reefs survive future stresses.

Micro-Fragmentation and Fusion: Creating Coral Clones

In 2016, a marine scientist in Florida accidentally crushed a piece of coral in a lab. Any annoyance at the mishap turned to intense interest when, three weeks later, he noticed that the remaining fragments had grown much faster than usual—up to 40 times faster. Experiments showed that the coral fragments fused together to form one big colony, and that all coral species in the Florida Keys would behave the same way. The accident was soon turned into a technique called micro-fragmentation and fusion. Using a specialized saw, corals are cut into tiny pieces― less than the size of a fingernail―and this stimulates the coral tissue to grow into coral clones much faster than they normally would. Placing fragments from the same colony close to each other encouraged them to fuse together to form larger colonies capable of reproducing in record time. It’s a major breakthrough for coral reef restoration―these corals can achieve 25 to 100 years’ growth in just a couple of years. The technique has been used to successfully plant more than 20,000 corals on depleted reefs, bringing some back from the brink.

Acoustic Enrichment: Healthy Sounds for a Healthy Reef 

It’s long been known that playing birdsong in a garden can attract birds—now the same principle is being applied to coral reefs. It’s easy to imagine these underwater worlds as quiet places, but a healthy reef is alive with the constant crackle of shrimp and the chatter, chirps, whoops, and growls of the thousands of fish species that call a reef home. However, when the health of a coral reef begins to decline, fish leave and the reef goes quiet. This is a problem because fish are vital to these complex ecosystems, cleaning away excess seaweed and algae, as well as recycling and depositing nutrients. Attracting fish back to a dying reef could turn around its chances of survival. To explore this, scientists used special recorders to capture the sounds of a healthy reef, and then played them back on underwater loudspeakers at newly restored reefs. Within six weeks, across 33 test sites where healthy sounds were played, scientists saw a doubling of fish numbers and a 50 percent increase in species—enough to kickstart the recovery of the ecosystem.

For more information about Sheba Hope Reef and to find out how you can help restore reefs, please visit