In the last 40 years, blast fishing, the practice of killing a large number of fish at once using explosives has inadvertently destroyed coral reefs. For instance, blast fishing has wiped out 75 percent of the reef in Sulawesi, the world’s 11th and Indonesia’s fourth-largest island.  

Sulawesi is just one of the many regions where blast fishing has caused massive coral reef damage, and what’s worse is that there is no way to recover the lost reef. Or so we thought.  

A team of researchers has demonstrated a technique that allows restored coral reefs in blast fishing-affected areas to grow at the same rate as healthy reefs. 

Giving new life to blasted reefs

Researchers from the UK’s University of Exeter conducted a four-year-long study in Indonesia as part of the Mars Coral Reef Restoration Programme. 

With the help of the local people, they tried to restore degraded reefs by deploying new healthy coral fragments.

“We used sand-coated steel frames to which healthy coral fragments are attached and which are then deployed over large areas of degraded reef area,” Dr. Ines Lange, lead study author and senior research fellow at the University of Exeter, said. 

Once the steel frames were planted, the researchers monitored the growth of the newly planted fragments and compared them with healthy corals at a control site. They measured the reef’s carbonate budgets, an important indicator of reef health that reveals active growth.

“It is the balance between reef framework production (by calcifying corals and crustose algae) and erosion (by grazing sea urchins and fish). We calculate the carbonate budget by counting and measuring all coral colonies and eroding organisms in a reef area, and combining the survey data with growth and erosion rates to calculate how much limestone the entire reef produces over a certain amount of time,” Lange told ZME Science. 

Researchers measured the carbonate budgets on degraded and healthy sites for a few months, then for a year, two years, and finally for four years. The results of the study were incredible.

In the first few years of the plantation, carbonate production, coral colony size, and reef cover tripled at the degraded site. By the end of four years, it was almost impossible to find any difference between the reefs at the healthy site and the degraded site.

The reefs were growing at a similar pace at both sites — something that even the researchers didn’t expect.

“We did not expect to see a full recovery of reef growth after just four years. Factors contributing to this fast recovery are the overall optimal conditions for coral growth in the area, the fact that the metal frames provide a good water flow to outplanted corals, and that the designated restoration team maintains the restored reefs for about a year after initial transplantation by removing algae growing on steel structures,” Lange explained.

One solution can’t solve every coral problem

Coral reef restoration often centers around passive management strategies such as designating a reef as a protected area. This is still important as it protects reef areas from further damage. In contrast, the proposed approach “jump-starts” the recovery of reefs, according to the researchers.

The sand-coated steel frames stabilize the loose rubble that prevent natural recovery. This three-dimensional structure also allows easy movement of reef animals. Ultimately, this promotes the growth of healthy coral at a degraded site. No other solution addresses the many problems with degraded coral sites so effectively.

Lange and her team hope that their successful reef restoration approach can inspire other projects, governments, and industries to invest in well-planned and well-managed reef restoration projects. 

However, they suggest that there is no one-fits-all solution, and reef restoration at any given location around the world will depend on local environmental conditions, natural larvae supply, restoration techniques, and management. 

“We have to keep in mind that while reef restoration can be successful on a local to regional scale, it will not be able to repair the large-scale damage and threat to coral reefs caused by climate change, which is why we have to work much harder to cut carbon emissions and stabilize the climate,” Lange told ZME Science.

The study is published in the journal Current Biology.