Coral reefs—the rainforests of the sea.

Reefs cover less than one percent of the seafloor, and yet they’re home to a quarter of all marine life, making them some of the most biodiverse places on Earth.

But their future looks bleak.

Decades of environmental threats like warming waters and ocean acidification—not to mention pollution and overfishing—have pushed reefs to the brink.

By 2100, many of the world’s major reef systems may become barren boneyards.

But there is hope.

Scientists are developing some creative techniques to bring dying reefs back from the brink and help them resist the impacts of environmental changes.

And what we learn may shed light on how ecosystems everywhere adapt, and how we can help them survive—before it’s too late.

Hey, I’m Joe and this is Hot Mess.

Reefs are a home and breeding ground for millions of species and they help protect shorelines by blocking the full force of storms and surges.

Hundreds of millions of people rely on coral reef fisheries for income and food.

And they’re also popular tourist destinations.

All in all, reefs are irreplaceable, which makes them invaluable.

You can’t put a price tag on them.

Although some people have tried to do that for Australia’s Great Barrier Reef.

But increased greenhouse gas emissions have caused ocean waters to warm and become more acidic, resulting in a downward spiral for coral reefs worldwide.

And here’s why.

Coral are the tiny invertebrates whose colonies form the foundation of reefs.

And they’re super sensitive to environmental changes.

Like all invertebrates, corals wear their skeletons on the outside, pulling carbonate ions from seawater, which they use to make strong calcium carbonate exoskeletons.

But when oceans become more acidic due to increased atmospheric CO2, there’s fewer available carbonate ions for corals to grow their armored exoskeletons, and reefs become more fragile and easily damaged.

Typically coral live symbiotically with algae, which take shelter in coral tissue and, in return, give corals their spectacular colors and as much as 90 percent of their nutrients through photosynthesis.

When waters warm, by even just a few degrees, the algae kick their energy production into overdrive.

This creates excess oxygen radicals that can damage the corals from the inside, so they evict their algae tenants.

With the algae gone, corals can starve, becoming whitewashed in a phenomenon called bleaching.

Bleaching isn’t always permanent, the algae can be invited back if conditions improve, but bleached coral struggle to survive and often never recover.

Half of all coral in the Great Barrier Reef alone has died since 2016.

The United Nations has named 29 reef systems World Heritage Sites, and if carbon emissions aren’t dramatically and rapidly reduced all 29 are predicted to be dead by 2100.

And even deep water reefs, once considered refuges for the species that live in shallow reef systems, are now considered at risk from climate change.

Marine biologists are looking for ways to restore coral reefs by mass-producing reef-building coral.

One process they’re testing is called micro-fragmentation and fusion.

To do this, scientists break bits of healthy coral into individual polyps.

When broken into fragments corals regrow sometimes 25 to 40 times faster than if they were left intact!

These coral fragments are raised in underwater “nurseries,”.

Once the newgrown coral gets big enough, they’re transplanted onto dead or dying reefs, literally glued on—with the hope that they take hold and re-establish.

When broken into fragments corals regrow sometimes 25 to 40 times faster than if they were left intact!

This labor-intensive technique is pretty new and it’s too soon to know if it can spark a significant enough recovery, but some scientists think it can revitalize reef systems more quickly than reefs left to recover on their own.

But another compelling approach to coral reef restoration has scientists examining coral DNA.

Coral geneticists are trying to unravel what makes corals tick.

Why, for example, do tabletop coral around the Cook Islands have genetic adaptations that make them unusually tolerant to warming waters?

What can explain coral oases, strange places where coral are thriving against all odds?

What in their DNA allows these coral to resist or fight back against changing ocean conditions?

We don’t have all the answers yet, but this knowledge may help us figure out how other coral could adapt to warmer waters, perhaps even allowing scientists to manipulate coral DNA and create “super” corals with genes that make them more resilient to heat and acidity.

We should be clear about this research—it won’t save all coral reefs.

But it could save some.

It might even save many.

And the knowledge we gain from this science will shed light on larger questions about how ecosystems evolve and adapt in a changing world.

So will the rainforests of the sea survive our changing planet?

Nature’s proven pretty resilient over the past few billion years, but saving coral will require plenty of help from us too.