Updated: Sep 16
Confronting Florida’s Coral Collapse. 2024. Adam Voiland. https://science.nasa.gov/wp-content/uploads/2025/10/florida_mur_20240711_anim.gif . Accessed 8-2026.
In the summer of 2023, Florida’s Coral Reef experienced a thermal event so extreme that it changed more than coral populations. It changed what we must ask of coral conservation.
For decades, coral restoration has focused on rebuilding what has been lost—propagating corals, returning them to degraded reefs, and rebuilding populations and reef structure.
But what happens when environmental conditions change faster than restoration can keep pace?
The answer became painfully clear in the Florida Keys in the summer of 2023.
A Reef Pushed Beyond Its Limits.
The 2023 marine heatwave was unlike anything Florida’s Coral Reef had experienced in the modern record. Thermal stress, measured in Degree Heating Weeks (DHW), (representing 1°C (1.8°F) of heat above the normal maximum temperature sustained for one week) reached approximately 18 DHW across the region and lasted two to three times longer than previous major events. In the most severely affected areas, temperatures rose so rapidly that corals died from acute heat shock in a few days.
The consequences were profound.
A new study by Lauren Toth and Travis Courtney, published in Frontiers in Marine Science in 2026, examines 29 years of monitoring data, from 1996 through 2024. The researchers found that more than 75% of the decline in reef-building capacity occurred following four major bleaching events: 1997–1998, 2005, 2014–2015, and 2023.
The cumulative effect is staggering:
Estimated reef-accretion potential has declined by over 92% from 1996 to 2024.
The ecosystem has shifted from building reef structure toward net erosion.
The 2023 event alone contributed approximately 12% of the overall decline in reef-accretion potential documented since 1996.
This is more than a decline in coral abundance.
It is a loss of ecosystem function.
When the Reef Becomes the Emergency.
The 2023 event was particularly devastating because corals that restoration programs had spent years propagating and returning to the reef were among the casualties.
Historically important reef species such as Acropora palmata (elkhorn coral) and A. cervicornis (staghorn coral) had already suffered decades of decline from disease and other stressors. Restoration programs had helped maintain and rebuild these populations.
But the 2023 heat event pushed many of those corals beyond their physiological limits, resulting in the functional extinction of acroporid corals throughout Florida’s Coral Reef and the loss of many outplanted corals.
The lesson is not that restoration failed.
It is that restoration cannot be separated from the environment into which we are restoring.
As environmental conditions become more extreme, rebuilding populations alone may not be enough. Conservation must protect what remains, anticipate future threats, and develop the capacity to respond when conditions exceed what corals can withstand.
A Response with HeaRT
In the middle of the 2023 crisis, the restoration community faced an immediate challenge.
Corals growing in ocean-based nurseries throughout the Florida Keys were experiencing dangerous high temperatures, prompting practitioners to move corals from the ocean into land-based facilities until conditions improved.
But moving corals out of the ocean created another challenge.
Many restoration practitioners were experts in growing corals in ocean-based nurseries. Caring for thousands of stressed corals in land-based systems requires a different set of skills and experience.
On August 7, 2023, the Florida Fish and Wildlife Conservation Commission and NOAA reached out to the Association of Zoos and Aquariums for assistance.
Within days, AZA responded.
Two “Heat Response Teams” (HeaRTs) were assembled, representing six AZA member facilities, and the Perry Institute for Marine Science in The Bahamas. Over approximately two weeks, HeaRT team members assisted practitioners caring for more than 5,000 corals. They evaluated coral health, provided hands-on support, shared feeding and care strategies and developed approaches that could continue after the teams returned home.
And when Hurricane Idalia threatened Florida during the response, the teams helped with hurricane preparation, response, and recovery.
This was not simply an emergency rescue.
It was a demonstration of what a connected conservation community could do when expertise was mobilized quickly.
The AZA Connect article, Our HeaRTs Go Out To Help Hot Corals documents the response and the lessons that emerged from it.
HeaRT Revealed a Conservation Resource Hiding in Plain Sight.
AZA institutions have decades of experience caring for animals under controlled conditions, recognizing changes in health, managing water quality, developing nutrition and feeding strategies, maintaining complex life-support systems, and responding to animal health emergencies.
Those skills are directly relevant to coral conservation.
During the 2023 thermal event, aquarists became a conservation resource at ecosystem scale. Aquarists were no longer simply caring for animals in their own institutions. They were helping restoration practitioners care for thousands of animals under extraordinary circumstances.
And just as importantly, they were transferring knowledge.
That may ultimately be one of HeaRT's most important contributions.
From Response to Readiness.
HeaRT may have begun as a response to a crisis, but its great significance is what it tells us about the future.
Repeated bleaching events have progressively reduced the abundance of reef-building corals and the ability of Florida’s reefs to build and maintain their own structure. As thermal stress intensifies and become smroe frequent, the future persistence of essential reef function is increasingly uncertain.
That changes the conservation question.
The question can no longer simply be :
How do we restore the reef after it has been damaged?
We must also ask:
How do we prepare for the next disturbance BEFORE it happens?
and
How do we help the REEF prepare for the next disturbance?
That requires a network:
A network of institutions capable of maintaining living coral populations.
A network of trained coral aquarists.
A network of scientists, restoration practitioners, veterinarians, educators, communicators, government agencies, and conservation organizations that can share information and act together.
A network capable of maintaining genetic diversity and redundancy across facilities.
A network that can rapidly mobilize and support others when conditions in the ocean become unsafe.
Redundancy is Resilience.
One of the clearest lessons from 2023 is the value of redundancy.
A coral maintained in one location is vulnerable to whatever happens in that location.
A coral represented across multiple facilities or locations is more secure.
An organization dependent on one expert is vulnerable when that person is unavailable.
A community with many trained practitioners can respond at scale.
A program with one institutional partner is vulnerable.
A network of partners can adapt.
Redundancy is not duplication. It is resilience.
The Toth and Courtney study notes that although some evidence suggests surviving coral populations may be becoming more thermally tolerant, it remains uncertain whether acclimatization and adaptation can occur quickly enough to keep pace with future warming and increasingly severe thermal extremes.
Conservation must be prepared to move faster, too.
Building What Comes Next
The 2023 event also forces us to reconsider what we mean by restoration. We must continue propagating corals, rebuilding populations, returning corals to the reef, and regaining reef structure and function. But rehabilitation in a rapidly changing environment also requires us to ask harder questions:
Which corals are most likely to survive future conditions?
Which genetic diversity must be protected?
Where should populations be maintained?
How much redundancy is enough?
How can we protect corals that may no longer be able to survive in their historical environment?
Can we accelerate corals’ evolving thermal tolerance?
How do we preserve the knowledge and expertise needed to care for them?
And perhaps most importantly:
How do we build the capacity to respond BEFORE the next crisis arrives?
These are not questions that any one organization can answer. They require collaboration.
This is where the experience of HeaRT connects directly to the work of SAFE Coral.
The Coral Aquarist Program helps build a broader community of professionals with the specialized knowledge and skills needed to care for corals.
The Florida Reef Tract Rescue Project provides a network through which rescued corals can be maintained across multiple facilities, reducing the risk associated with relying on a single location.
SAFE Coral partnerships connect zoos and aquariums with researchers, restoration practitioners, government agencies, and other conservation organizations.
Together, these efforts build something increasingly important in a rapidly changing ocean:
conservation readiness.
Conservation readiness means more than having a response plan.
It means having the people, knowledge, infrastructure, relationships, genetic resources, and institutional capacity already in place to act.
It means turning lessons learned during an emergency into practices that strengthen and prepare for the next response, and ensuring that specialized knowledge is not concentrated in a handful of individuals or institutions.
And it means creating a conservation community capable of adapting as the threat changes.
What We Carry Forward.
The summer of 2023 will rightly be remembered for the extraordinary heat and the profound loss it caused across Florida’s Coral Reef.
But it should also be remembered for how the conservation community responded.
When the ocean became too hot for corals to remain in their nurseries, practitioners moved them to land.
When additional expertise was needed, AZA responded.
When restoration practitioners needed new husbandry skills, aquarists willingly shared what
they knew.
And when the immediate crisis passed, the experience left behind something more valuable than a single emergency intervention:
knowledge, relationships, and a model for future action.
New research tells us that the reef has changed profoundly. After decades of repeated bleaching, Florida’s Coral Reef has crossed from marginal reef growth into regional-scale net erosion.
We cannot undo that history. But we can decide what we do with what we have learned.
HeaRT began because there was an emergency.
SAFE Coral's opportunity now is to make sure we remain ready for what comes next.
The future of coral conservation will depend not only on what we can restore today, but on whether we can build the knowledge, partnerships, people, and infrastructure needed to protect coral biodiversity through the extremes of tomorrow.
This year's and future heatwaves will test the reef.
Our readiness will determine how much we are able to do, together.
