In the wreckage of dynamited reefs off South Sulawesi, Indonesia, scientists have discovered something almost unimaginable: restored coral can recover fully in just four years.
For decades, the reefs in this region bore the scars of blast fishing—a brutal practice that devastated them 30 or 40 years ago, leaving behind loose rubble that choked out new life. The damage seemed permanent. Young coral larvae had nowhere to settle, and without intervention, these underwater ecosystems showed no signs of bouncing back on their own. But the Mars Coral Reef Restoration Programme, one of the world's largest restoration efforts, changed that by using sand-coated steel structures to consolidate the rubble and create a foundation for transplanted coral fragments. The question was whether this human-led intervention could actually work—and how long it would take.
The answer, published in Current Biology in March, has surprised even the researchers themselves. Ines Lange of the University of Exeter and her international colleagues measured the health of 12 restored sites up to four years after transplantation by calculating what scientists call the reef carbonate budget—essentially tracking whether a reef is growing or shrinking by measuring how much calcium carbonate corals add to the reef structure versus how much fish and sea urchins erode away. What they found was remarkable: the net carbonate budget at restored sites had tripled within four years, matching that of healthy control reefs.
"We did not expect a full recovery of reef framework production after only four years," Lange said. The speed of recovery matters enormously. As seas rise and storms intensify, healthy reefs provide irreplaceable services: they form habitat for marine life, protect coastlines from waves and erosion, and support local fishing communities. A reef that is actively growing stays resilient.
The restored reefs achieved this by supporting rapid growth of transplanted corals, particularly branched varieties. Within four years, the restored sites were functioning like healthy reefs—producing the framework that marine species depend on and performing the protective work that shields islands from the ocean's fury. The findings offer genuine hope in a world where most coral reefs face existential threats from warming water, pollution, and acidification.
Yet the scientists are careful to acknowledge what they don't yet know. Because branched corals dominated the restoration effort, the species composition of these rebuilt reefs differs from natural reefs. Branching corals, while fast-growing, are more sensitive to heat stress and bleaching—a vulnerability that could matter if another warming event strikes. The researchers hope that over time, natural recruitment will bring greater species diversity to these sites, but longer-term monitoring will be essential to understand how the reefs perform under stress.
Nor is this a universal solution. Environmental conditions vary dramatically across the globe, as do restoration techniques. What works in South Sulawesi may need adaptation elsewhere. Yet Lange and her co-author Tim Lamont see the findings as a template for hope—evidence that we have the tools to rebuild functioning reefs if we act quickly. "These results give us the encouragement that if we can rapidly reduce emissions and stabilize the climate, we have effective tools to help regrow functioning coral reefs," Lamont said. The lesson is clear: reefs can recover. The question is whether we will give them the chance.