- Coral restoration is vastly outpaced by degradation, while intensifying climate stress, prohibitive costs, poor site selection and lack of coordination make large-scale restoration currently unviable, a new study has found.
- The scale-cost mismatch is staggering: Restoring just 1.4% of degraded coral could cost up to US$16.7 trillion, while current global funding is only US$258 million.
- The study found most projects assessed prioritize convenience over ecological value, restoring easily accessed reefs instead of climate-resilient or biologically strategic ones, undermining long-term outcomes.
- Researchers say standardized data and smarter planning are urgently needed to ensure that global coral restoration is scientifically informed and strategically targeted, and not merely symbolic.
Coral restoration won’t save reefs from global warming, according to a recent study – at least, not the way we’re doing it now.
The study, conducted by researchers at the University of Helsinki and published earlier this month in Nature Ecology & Evolution, finds coral degradation is significantly outpacing restoration efforts. Its results indicate most unsuccessful projects fail due to prohibitive costs, lack of global coordination, location unsuitability, and bleaching events caused by rising water temperatures, during which coral becomes white due to stress.
Despite “public perception and scientific enthusiasm” for coral restoration, we can’t restore our way out of this one, the study finds.
“Scaling up restoration to any meaningful level going beyond the very local scale would be extremely challenging,” senior author Giovanni Strona, now a quantitative ecologist at the European Commission in Italy, told Mongabay.
Sebastian Ferse, a senior ecosystem scientist at the Leibniz Centre for Tropical Marine Research in Germany, who wasn’t involved with the study, told Mongabay that its results suggest “reef restoration is prohibitively expensive, particularly when looking at the scale of the problem we are facing.”
“It is much more cost-efficient to prevent degradation of reefs in the first place than having to restore the damage afterwards,” Ferse said.
Crucial coral
Coral provides an estimated $11 trillion in ecosystem services globally every year, according to research published in MIT Science Policy Review. These services include protection from flooding, sustaining fisheries, generating tourism, and creating jobs. More than half a billion people directly depend on coral ecosystems, according to the International Union for Conservation of Nature, and they harbor the highest biodiversity of any ecosystem globally.
Yet, research indicates that due to climate change, overfishing, pollution and habitat destruction, humans have destroyed 50% of the planet’s coral since 1950.
“We are now in a planetary emergency, despite the widespread denial,” Strona said. “We are in the middle of the sixth mass extinction, and most projections for the coming decades regarding biodiversity and the environment are catastrophic.”
If global warming continues on its current course, 90-99% of the world’s corals will be gone by 2050, according to the Intergovernmental Panel on Climate Change (IPCC). Even if we limit warming at 1.5° Celsius (2.7° Fahrenheit) above preindustrial levels, we stand to lose 70-90% of our reef ecosystems, IPCC figures show.
“The feel-good narrative revolving around coral restoration should not be used as a distraction from very-much-needed global actions to reduce carbon emissions and slow down planetary warming,” Strona said.
What’s stopping us from scaling up?
Previous research published by the United Nations Environment Programme found 11,700 square kilometers (about 4,500 square miles), or 14% of all coral globally, was degraded between 2009 and 2018. The cost to rehabilitate just 10% of what was degraded during that time could soar to $16.7 trillion, according to the findings by Strona and his team.
Between around 2006 and 2021, spending on coral restoration globally was estimated at $258 million, according to the International Coral Reef Initiative, funded primarily by philanthropic foundations, national governments and private investments or donations. This, according to Strona’s study, is around one-65,000th of the funding required to restore just 10% of the coral cover degraded between 2009 and 2018.
Finally, we simply aren’t quite there technologically, according to Ferse. Installing a stable base for corals and transplanting or seeding the billions necessary is no small task: “We still require techniques that allow for upscaling by reducing costs and enhancing speed and efficiency of restoration,” Ferse said.
We need “a much better way of acknowledging the true costs of reef degradation and a way to put the price for the damage on those causing it,” he added.
We’re not connecting the dots right
Were money no object and the planet not warming, we’d still be in trouble, according to the study. When Strona and his team modeled how coral restoration sites are chosen, the main determining factor was how accessible to humans a site was, rather than its ecological value.
No clear ecological rationale means we may be dooming ourselves to waste significant resources by selecting sites that will never be long-term successes, the researchers warn.
The study found that sites that are more accessible to humans are usually less resilient as they’re more exposed to human impacts like pollution and boat traffic; restoring areas likely to warm beyond the point at which coral can survive is also unlikely to be successful in the long term. Smarter, climate-informed planning is therefore needed to ensure that restoration investments actually lead to long-term ecosystem recovery, the study suggests.
For restoration efforts to target the right areas, relevant data need to be collected, analyzed and used to inform effective planning and strategy. But, overall, we’re just not doing that at the moment, the study found.
Data collection, monitoring, storage and sharing methods tend to vary from project to project, and long-term outcomes often go unreported, according to the study. Its authors recommend global standardization of research and monitoring methods, together with centralized, open-access information storage. This, they write, would help make sure coral restoration efforts are meaningful in the long term, and not simply symbolic gestures.
Should we be bothering with coral restoration at all, then?
While the study found that many current restoration projects may not succeed in the long term, “This does not necessarily mean that all restoration projects are useless,” Strona said. He added they could be of enormous benefit to build up our understanding of how corals respond to stress.
But, Strona said, efforts need to be backed up by “proper science in terms of coral biology and ecology,” so that we can be in a better position to see what works and what doesn’t. This, he said, would better equip restorers to deploy funding where it’s most likely to have the desired impact, instead of simply dipping a toe in where it’s most convenient. Ad hoc restoration projects could also be used to help conserve endangered species, he said.
In the limited time we have, with the projected global change we face, Strona said he believes the scientific community must join forces to ameliorate the most pressing issues.
“We have to realize that natural systems as we see them now are complex and delicate entities which have been assembled by nature over the course of hundreds of thousands of years,” Strona said. “We only have limited knowledge of their functioning and we do not have the tools or spare parts to repair them in case of failure.
“And now we are experiencing a simultaneous and global-scale failure. It is not only naive to think that there is an easy solution to it, it is extremely arrogant.”
Banner image: Vibrant orange and pink coral reef covered with anemones and surrounded by fish. Image by Joe Hoyt/NOAA via Wikimedia Commons (CC 2.0).
Citations:
Mulà, C., Bradshaw, C. J. A., Cabeza, M., Manca, F., Montano, S., & Strona, G. (2025). Restoration cannot be scaled up globally to save reefs from loss and degradation. Nature Ecology & Evolution. doi:10.1038/s41559-025-02667-x
Rivera, H. E., & Chan, A. N. (2020). Coral reefs are critical for our food supply, tourism, and ocean health. We can protect them from climate change. MIT Science Policy Review, 1, 18-33. doi:10.38105/spr.7vn798jnsk
Eddy, T. D., Lam, V. W. Y., Reygondeau, G., Cisneros-Montemayor, A. M., Greer, K., Palomares, M. L. D., … Cheung, W. W. L. (2021). Global decline in capacity of coral reefs to provide ecosystem services. One Earth, 4(9), 1278-1285. doi:10.1016/j.oneear.2021.08.016
FEEDBACK:Use this form to send a message to the editor of this post. If you want to post a public comment, you can do that at the bottom of the page.
Credits
