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The grand challenge of maintaining coral reefs


Many people depend on coral reefs for food production, shoreline protection, and livelihoods. Yet, since the 1980s, coral reefs have experienced significant increases in bleaching and mortality resulting from global warming. Twenty-one international experts from seven countries report that this will continue to escalate, threatening the survival of coral reefs this century. They assessed the potential solutions to the coral reef crisis, and emphasized that these will need to be part of an organized strategy, with strong backing by governments and investment on par with those applied to other world crises.

Maintaining coral reef ecosystems, arguably the most threatened ecosystem on the planet, is a social imperative, because so many people depend on coral reefs for food production, shoreline protection, and livelihoods. Global warming triggers mass mortality events which increase in magnitude and frequency.

Through an initiative co-funded by the Prince Albert II of Monaco Foundation and the Pew Marine Fellows Program, twenty-one international experts from seven countries addressed the potential for coral reefs to survive rising ocean temperatures through this century. Using temperature projections from high and low CO2 emissions scenarios, they projected rates of coral bleaching while considering the capacity of corals to adapt. Under the high-emissions trajectory, temperature continues to increase and adaptation and interventions can delay but not prevent unsustainable levels of bleaching of all reefs. Under the low-emissions trajectory, which is compatible with the Paris Agreement, the temperature increase slows, allowing some corals to adapt.

Thus, coral reef survival depends on both mitigation of CO2 and actions to increase their capacity to adapt, within the short time window between now and 2050. How fast we act within this window will determine which reefs, species, ecosystem functions and services can be sustained. Without action, coral reefs as we know them today – and their associated services to humankind (food production, reductions in flooding and erosion, tourism, economic resources, cultural values) – are likely to be one of the first major ecosystems in this century to collapse under the weight of climate change.

Potential measures to limit and counteract the decline of coral reefs were assessed for their effectiveness, readiness of technological development, potential adverse consequences, societal acceptability, and operational scale. Among two global-scale actions, reducing carbon emissions scored highly while aerosol-based solar radiation management, in which sunlight is reflected back to limit global warming, scored very low and is not condoned by the expert group. Among the local actions, a few would rank higher if scalability could be increased, such as through networks of local actions to increase resilience (e.g. conservation, restoration, assisted reproduction, and assisted gene flow).

The assessment highlighted the consensus that mitigation of greenhouse gas emissions is not only essential to reef survival, but is also the most wide-reaching, effective, achievable, beneficial, and acceptable action. It also highlighted that reduced emissions must be paired with continued local to regional actions to protect the coral reef environment and to increase coral reef resilience. Many of these actions need improvement, and some need further development and testing with the acknowledgment that some may never be implemented if risks are deemed to be too high.

Saving coral reefs requires an organized strategy, strong backing by governments, and significant investment. Saving an ecosystem is a big challenge on par with global efforts to cure disease. The urgency of the coral reef crisis also calls for much stronger coordination across disciplines. The basis for this coordination would ideally take advantage of multiple existing organizations and networks, and numerous government organizations, NGOs, and private institutions that are already partnering to achieve common objectives. Such partnerships must be strengthened with clearly defined top priorities over the next 20–30 years, and a flexible plan for coordinating the multiple measures of adaptation.

One such partnership is the International Coral Reef Initiative (ICRI), an informal union of nations, international organisations, and civil society to preserve coral reefs and associated ecosystems, and for which Monaco is currently co-hosting the Secretariat. HSH Prince Albert II of Monaco stressed the importance of coral reef ecosystems and the urgency to act during a general meeting of ICRI in February 2021 “Faced with the current challenges, which are at the convergence of economy, science and politics, I believe that we must always work together. It is together that we can act effectively and hope to save the corals. [...] My Foundation, which supports field projects and innovative multilateral initiatives, such as the Global Fund for Coral Reefs launched with the Paul Allen Foundation, has also made the protection of coral reefs a priority.”

Original publication:

Kleypas J., Allemand D., Anthony K., Baker A. C., Beck M., Hale L. Z., Hilmi N., Hoegh-Guldberg O., Hughes T., Kaufman L., Kayanne H., Magnan A., Mcleod E., Mumby P., Palumbi S., Richmond R., Rinkevich B., Steneck R. S., Voolstra C. R., Wachenfeld D. & Gattuso J.-P., 2021. Designing a blueprint for coral reef survival. Biological Conservation



Some photographs illustrating the paper are available and can be used freely. Note that the copyright owner indicated in the file name must be mentioned. See:



Joanie Kleypas (NCAR, USA), Tel. +506 8635-2998,; Jean-Pierre Gattuso (CNRS-Sorbonne Université-Iddri), Tel. +33 695 92 68 80,


Cover photo : Pete Mumby