Coral plantation manages to recover a reef in just four years

Planting new corals on degraded reefs can achieve rapid recovery of these ecosystems: A study has proven that restored corals grow as fast as healthy ones and perform the same functions just four years after being placed.

This has been demonstrated by an experiment carried out on the southern reef of Sulawesi (Indonesia) reported this Friday in the journal Current Biology and in which researchers from the British universities of Exeter and Lancaster, the National Research and Innovation Agency ( BRIN) of Indonesia, and the Mars Sustainable Solutions initiative.

Reefs around the world are seriously threatened by local pressures (pollution, poor fishing practices or unsustainable tourism) and global pressures, such as climate change.

In Indonesia, fishing with explosives destroyed large areas of reefs more than 30 years ago, without any signs of natural recovery since then.

This research has focused on one of the country’s most valuable reefs, in South Sulawesi, where one of the world’s most ambitious restoration projects is underway, called the Mars Coral Reef Restoration Program.

Coral planting

The researchers have created a continuous, interconnected network of steel structures covered in sand that have served as a base for transplanting fragments of healthy coral in 12 very deteriorated areas of the reef, where new coral larvae were not growing.

Once the planting was carried out, the scientists monitored the restored areas to see how the corals grew and how long it took for the reef to recover the functions of a healthy ecosystem: carbon capture (CO2), protection of the coast against storms or provide habitat for marine species.

They evaluated the 12 restored areas each time they completed another year of their regeneration and compared the data on the capacities they were acquiring with the healthy ecosystems of the same coral reef.

An incredible recovery

The result was that in the years following the transplant the extent of coral cover and the size of coral colonies tripled and, after four years, “the restored sites were indistinguishable from nearby healthy reefs in all parameters investigated,” explains one of the authors, Ines Lange, from the University of Exeter.

“This means that, in just four years, the restored reefs grow at the same rate as healthy reefs, provide a similar habitat for marine life and effectively protect the adjacent island from waves and erosion,” adds the researcher in a statement.

“The speed of recovery we have observed is incredible,” underlines.

“It is a hopeful discovery, which tells us that if we manage to maintain climatic conditions that allow the survival of corals, it is possible to restore very damaged reefs so that they become healthy and functional ecosystems again in a short time,” says another of the authors, Tim Lamont, of Lancaster University.

Limitations

One of the limitations observed is that since the corals are transplanted from various types of branched coral (those that grow best in culture), the ecosystem that grows is fundamentally of these species, while a normal reef combines the branched ones with other corals in the shape of rock and encrustations.

“This may affect the provision of habitat for larger marine species and the ability to recover from future heat waves, since branching corals are more sensitive to bleaching,” says Lange, who hopes that, over time, “Restored reefs naturally recruit a more diverse mix of species.”

The authors agree that reef restoration will not serve to save those that are seriously threatened by global warming. Today, in fact, it has become known that the Australian Great Barrier Reef is suffering its fifth bleaching since 2016 due to the climate crisis.

A more long-term study is needed to see what happens over time and under stress conditions, but the “results demonstrate that restoration can increase the resilience of certain reefs and restore vital functions for marine life and the coastal communities they protect”notes Lamont.

“As is often the case, there is no one-size-fits-all solution, but we hope this positive example will inspire other reef restoration projects around the world.”concludes Lange.

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