A bright colourful coral reef with tropical fish swimming amongst the coral. In the background, a swimmer with a mask, snorkel and fins is using a large camera to take photos of the coral reef. The picture evokes both the beauty and variety of life to be found in a coral reef.

The Flood-Fighting Power of Coral Reefs

ByHayley Frend

Photo by Neom on Unsplash

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I floated in the perfect blue, weightless and calm, as tiny clownfish darted playfully around my dive mask. All I could hear were the soft, rhythmic bubbles from my respirator.  Beneath me, a vibrant coral reef stretched into the distance, an intricate, living city of colour and movement, pulsing with life. 

Dr Hayley Frend scube diving. She has on a wetsuit with a scuba diving mask on her face. On her back is a oxygen tank. A stream of bubbles rises from her respirator. Her blonde hair flows behind her.

Photo of Dr Hayley Frend diving in the Philippines.

I was 18, and I was in love, not with any of my dive buddies waiting for me on the boat above, but with the coral reef itself. With the little communities which I could observe swimming in and out of the coral, going about their daily lives completely oblivious to me. With the absolute splendour and fragile beauty of the expansive coral spreading out underneath me, stretching into the distance, carrying with it the secret and stories of countless fascinating underwater inhabitants. 

I am not the only one who has glimpsed a coral reef and fallen in love at first sight. Watching just one David Attenborough documentary can have the same effect without ever getting your feet wet. But these underwater artworks are more than just a pretty face. It turns out they can be powerful heroes too. If we place our trust in them, they could just reward us with saving our lives one day. 

Understanding Coral Reefs and Their Importance

We know coral reefs are beautiful, we know they are extremely fragile and in danger- but did you know they can serve as life-saving flood defences? Let’s dive in….

a close up of a coral reef. It fills the entire image with birhgt yellow, red, green and purple sponges and corals. A few tropical fish swim above the reef. The effect is like that of a colourful painting.

Photo by Shaun Low on Unsplash

A coral reef system may look like an underground garden, full of colourful plants but a coral reef is actually made up of tiny marine animals called coral polyps. They secrete a hard calcium carbonate skeleton, which over time builds up into the intricate and towering coral structures we recognise from TV documentaries. These polyps have algae living within them that provide them with nutrients through photosynthesis. 

Coral reefs support an estimated 25% of all marine life, despite covering less than 1% of the ocean floor. 

  • A vast array of fish, invertebrates and other marine life live within their colourful towers, tunnels and structures.
  • This in turn stabilizes the entire marine food chain and local economies reliant on fishing.
  • They sustain much underwater plant life- absorbing carbon dioxide and releasing vital oxygen. 
  • They provide a home for important filter feeders, such as sponges. Sponges can filter thousands of litres of water per day, removing bacteria and pollutants.
A bright orange and white striped clownfish swims in front of a sea anemone. Another clownfish is just visible, nestled within the anemone. It illustrated the varied lieforms coral reefs house.

Photo by Tom Fisk

So these amazing communities support an abundance of life, clean the water, and provide oxygen. That would be amazing in itself. But despite this, they also function as quiet life savers from beneath the waves. They silently shield our coasts from destruction, offering a first line of defence that doesn’t need concrete or steel. Their rough surface and towering structures serve as natural wave breakers, reducing the effect of devasting flooding on coastal communities.

By the way, if you’re inspired by how humans can harness nature’s brilliance, check out this blog about how scientists are using bacteria’s natural abilities to help build and repair bricks on the Moon.

The Threats Coral Reefs Face

But unfortunately, this vital but delicate ecosystem is under serious threat from those it protects– us.

  • Over 50% of coral reefs have been lost or severely damaged since the 1950s, according to a study by One Earth  
  • Climate change is increasing the temperature of the oceans, turning up the heat beyond that which coral can cope with. This causes them to expel their vital algae and turn white in a coral bleaching event. 
  • Climate change is also causing the oceans to turn more acidic, making it hard for coral to build their external structures.
  • Additional threats include: pollution in the seas, destructive fishing techniques and deliberate destruction of coral through mining.

The Cost Problem—And the Opportunity

The need to protect and support our coral ecosystems is obvious. However as we know- money is tight globally. Unfortunately funding for habitat restoration is already spread incredibly thin. Funding for human hazard reduction or disaster relief is relatively larger.

  • US federal flood prevention funding: over $15 billion in 2022
  • Coral reef restoration funding: just over $8 million

But this is where corals’ coastal protection role could step in. 

Flooding causes human tragedy and economic devastation every year. 

A low wall and beyond that a wild and stomry sea. A particularly large wave is breaking over the wall. The floor in front of the wall is wet, indicating the waves have been breaking over the wall for some time. a coastguard van with orange lights flashing is driving alongside the wall. The scene evokes the devastating power of storm waves and leaves an uneasy feeling.

Photo by DDP on Unspash

Not only beachfront homes are at risk. Inland communities, often poorer, face increasing dangers from large flooding events.

These flooding events are often called 100-year floods. This means, not that they will literally occur once a century, but that on any given year there is a 1% chance of a flood.  Although with climate change they are becoming increasingly more frequent. If we could help coral reefs rebuild from the damage we have caused, they could return the favour and in turn protect our most vulnerable coastal communities. However, to do so is not cheap. And funding bodies designed to help rebuild and protect communities which have been ravaged by floods often require metrics like a cost-to-benefit ratio. They understandably want to ensure that their money will be  wisely spent. But when we consider a natural protection mechanism like coral reefs, this figure is not easy to calculate. 

Scientists from Santa Cruz, California set out to do exactly this. They wanted to study not just whether coral reef restoration can protect against flooding but also calculate exactly how much protection they offer. They wanted hard data on which communities they could offer the most benefit to, and how they can be best designed to offer maximum protection.  

The Study

Researchers from Santa Cruz, California, including Dr Curt Stolazzi, set out to study how much protection restored coral reefs could really offer. They analysed potential reef restoration projects in Florida and Puerto Rico.

Key Findings

  • Reef restoration can reduce the chance of a 100-year flooding event by 20%.
  • Restoring up to 35 km of reefs in Florida and Puerto Rico would pay for itself within a year.
  • A 30-year project restoring 20% of reefs would also be cost-effective.

This is crucial proof that the nature-based solution of reef restoration is not just good for the reef ecosystem but can provide a return on investment in terms of money and lives saved. 

Where to Restore

  • Focus on shallow, narrow, and nearshore reefs in front of low-lying communities.
  • These offer the greatest flood protection benefit.

This is important as it allows us to prioritise which reef sections to restore- it is important to make funds go as far as possible and to protect as many people as possible 

Who Benefits Most from Coral Reef Restoration?

  • Not immediate beachfront residents—but inland communities affected by rare but increasingly common freak flooding.
  • These areas often include high proportions of:
    • Children
    • Elderly
    • People living below the poverty line
  • These vulnerable groups could see more than double the risk reduction compared to the general population.

Reef restoration saves not just the most vulnerable underwater inhabitants but the most vulnerable coastal communities too. 

Meet the inspirational scientist behind this research

Global Implications

This study isn’t just about Florida and Puerto Rico. It has global relevance.

 Many topical countries experience regular devastating floods but also have tight budget constraints when it comes to food protection schemes. Coral reef restoration could provide a natural and cost-effective solution. It’s important to note that restoring reefs is cheaper than current artificial flood protections.

Constructing artificial breakwaters can cost between $5 million and $10 million per kilometer, whereas hybrid coral reef restoration projects typically range from $0.5 million to $3 million per kilometer, offering a more cost-effective and environmentally friendly solution.

Large concrete tetrapods forming a coastal flood barrier are stacked along the shoreline, with sunlight reflecting brightly off the calm sea in the background.

 Which do you prefer? Photo by DDP on Unsplash

And importantly they are also more future-proof. Traditional hard structures like breakwaters need to be rebuilt and made higher with rising sea levels. On the other hand, coral reefs will naturally grow with rising sea levels- continuing to provide protection. 

Nature has inspired countless scientific breakthroughs, like the researchers who were inspired by swarming insects to create microrobots that could one day treat lung disease. Curious? Dive into the full story in our next blog.

Long-Term Maintenance & Future-Proofing

The researchers from Santa Cruz acknowledge that estimating the long-term maintenance costs of coral reef restoration is challenging. This is largely because large-scale, long-term restoration projects are still relatively rare. Moreover, coral reefs everywhere face an uncertain future. Even restored reefs may require ongoing care and attention to remain healthy, especially under worsening environmental conditions.

However, there is hope on the horizon. New initiatives, such as breeding coral polyps that are more resistant to temperature changes and less prone to bleaching, promise to make future maintenance both easier and more cost-effective.

It’s also important to remember that the study focuses only on the financial benefits of flood prevention. In reality, regenerated coral reefs offer a range of additional economic advantages. For example:

  • They attract tourists, boosting local economies.
  • They help replenish fish populations, supporting fishing industries.

What this research ultimately highlights is a broader shift in how we value nature. Coral reefs are not just ecological marvels or popular travel destinations, they are vital, functional infrastructure. And by choosing to invest in nature-based solutions, we are not only protecting the environment, we are investing in our own long-term security and prosperity.

Investing in Nature, Investing in Us

We often think of coral reefs as distant wonders. Vivid ecosystems tucked away in tropical oceans, beautiful but far removed from our daily lives. But this research reveals something profoundly different. These fragile, intricate underwater cities are not only home to countless marine species, they are powerful allies in our fight against climate-driven disasters. When healthy and restored, coral reefs can cushion our coastlines from the worst impacts of flooding, protecting not just beaches, but homes, schools, and the lives of those who live far beyond the shore.

And perhaps most movingly, it’s the most vulnerable among, low-income families, the elderly, children, who stand to benefit the most.

Looking up at a coral reef formation that entends upwards on three sides, like a vertical tunnel. Coloural sea fans and various species of coral extend into the middle. Fish swim above the camera. The density of life is notable.

Photo by Abdul Hakkim on Unspash

Coral reefs are not just passive victims of climate change. With the right support, they can be resilient protectors, offering a nature-based, cost-effective solution that serves both people and planet. But time is running out. If we want these “quiet heroes” to keep standing guard at the edge of our continents, we must invest in restoring what we’ve damaged.

Not just because they’re beautiful.
Not just because they’re worth saving.
But because they just might save us too.

Tonights Dinner Table Discussion

Here’s some ideas to spark a fascinating discussion.

  • Would you feel differently about coral reefs if they were rebranded as “natural disaster shields”? Why or why not?
  • What are some innovative ways we could fund coral restoration projects, especially in areas that need them most but lack resources?
  • What gives you hope in the fight to protect coral reefs and coastal communities in the face of climate change?
  • Who needs protection the most—us, or the ocean. What would protecting each other look like?

Big Family Question:

If coral reefs could talk, what would they say to us and what would we say back?

Looking for more family-friendly discussion prompts? Explore our child-focused version of this blog here.

Curious but cautious?

Love diving into science, but not always sure what to believe? Grab our free guide:
“5 Ways to Spot Fake Science News”
It’s full of quick, practical tips to help you tell real breakthroughs from misleading headlines.

Nature has solutions we’re only beginning to understand.Sign up to the Trailblazing Science newsletter to explore more science behind nature’s hidden engineering.

Keep Exploring

Nature isn’t just beautiful, it’s brilliant. Want to see how its genius is shaping the future? Dive into:
→ How bacteria might help build self-healing bricks on the Moon
→ How microrobots inspired by insect swarms could fight lung disease

Let’s Talk About It

Would you support a climate policy that puts as much funding into natural defences like reefs and wetlands as it does into concrete infrastructure? We would love to hear your thoughts. Let us know below.

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