Degraded coral reefs can recover at an “incredible” pace, growing at the same speed as healthy ones that have not been restored after just four years of management, although they tend to be poorer in biodiversity, research has found.

The study, led by University of Exeter researchers and published in Current Biology, was conducted in South Sulawesi, Indonesia at the MARS Coral Reef Restoration Programme, one of the world’s largest initiatives of its kind.

Through methods such as coral transplantation, the MARS programme aims to assess whether active management actions in ecosystems damaged by blast fishing 30-40 years ago can restore the ecosystem functions of a healthy reef.

“These findings are really exciting – they should spur us on to invest further and faster in emissions reductions,” Tim Lamont, a marine biologist at Lancaster University and senior author of the study, told Carbon Pulse.

“If we can stabilise the climate, we have every chance of rebuilding healthy ecosystems around the world,” Lamont said.

Researchers assessed for the first time the so-called “reef carbonate budget”, meaning they analysed the net production or erosion of reefs over time at restoration sites.

After carrying out surveys on three degraded reefs and three healthy ecosystems that were used as reference sites, researchers unveiled that net carbonate budgets have tripled four years after coral transplantation, making the sites equivalent to healthy ones in terms of coral.

“Four years after coral transplantation, coral cover, average colony size, and carbonate production rates have tripled, and restoration sites are indistinguishable from proximal healthy reefs in all investigated parameters,” the paper said.

A reef four years after restoration at the MARS programme, Indonesia. Source: The Ocean Agency

“The speed of recovery we saw is incredible,” lead author Ines Lange from the University of Exeter said.

“We demonstrated the potential of large-scale, well-managed coral restoration projects to recover important ecosystem functions within only four years,” the paper highlighted.

DOWNSIDES

However, researchers recognised that the community composition on restoration sites is less biodiverse than that on healthy reefs – a difference that may affect habitat provision for larger marine species.

While healthy ecosystems are also home to many boulder-like and encrusting corals, the restored reefs are a mix of only branching coral types. As these corals are more sensitive to bleaching, this may affect their resilience to future heat waves.

“Fast-growing branching corals provide the most immediate gains in terms of coral cover, structural complexity, and carbonate production. On the other hand, the resulting reef may be less diverse in terms of biodiversity and habitat provision compared to natural reefs, which harbour more massive corals and large-scale framework structure,” the study said.

“While the diversity of coral species is still lower at restoration sites, we’re hopeful that, over time, restored reefs will naturally recruit a more diverse mix of coral species,” Lange explained to Carbon Pulse.

“The MARS reef restoration programme has already started to assist this process by additionally transplanting massive corals, and by providing more suitable substrate for natural coral recruitment.”

According to the MARS 2023 impact report, coral reefs are the most biodiverse marine systems, packing 25% of marine life into less than 0.1% of the ocean floor. Around 1 billion people rely on them worldwide, primarily for fishing, and 100 million homes are protected from waves and storms by them, it said.

“While reef restoration cannot solve the problem that reefs are severely threatened by climate change, it shows that active management actions can help boost the resilience of specific reefs, and bring back important functions critical for marine life and local communities,” Lange stressed.

By Giada Ferraglioni – giada@carbon-pulse.com

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