Coral reefs are in a life or death battle
with climate change.
"It’s heartbreaking.
I mean, you’re losing an entire ecosystem."
These dazzling, invaluable ecosystems have been around
for thousands of years; and support millions of people around the world.
But environmental destruction could completely wipe them from the
face of the Earth in just a few decades.
"People depend so heavily on coral reefs
for their livelihoods, for their food."
Now, researchers are trying out every tool they can get their hands on –
from conservation to strengthening corals in the lab –
to try to toughen reefs up.
But with the world changing at unprecedented
speeds, the question remains:
Can we save coral reefs from climate change?
Coral reefs are unlike anywhere else on Earth.
They are home to mind-blowing biodiversity.
The world's reefs are shown with red dots here.
"They cover less than 1% of the ocean floor,
but they actually support over a quarter of all marine life."
Considering these staggering statistics
and the size of coral reefs themselves –
it's easy to forget that they’re actually built from tiny animals:
coral polyps.
Corals owe a great deal of their magic,
and their beautiful colour,
to a complex cooperation between organisms.
Algae live in the polyps' tissue,
and provide nutrients to the
coral in exchange for protection.
But this delicate teamwork
is under threat from climate change.
CO2 emissions dissolve in the seas,
making waters more acidic
and weakening coral skeletons.
And that's not all...
As global temperatures soar,
coral reefs suffer through ever more frequent
and intense ocean heatwaves.
Extreme temperatures cause the algae
to produce harmful chemicals,
prompting the coral polyps to kick them out.
This is "coral bleaching" where vibrant polyps turn white
from heat stress, a process that can eventually prove fatal.
And global warming is already driving vast bleaching events today.
Take the 2016 bleaching of
the Great Barrier Reef, which saw mass die-offs.
Coral cover declined by a third due to high ocean temperatures.
Such losses threaten the livelihoods of
half a billion people across the globe.
Reefs provide everything from food to income
to those that live alongside them, while supporting the world's oceans
for the entire planet's benefit.
And reefs also protect.
When storms hit, corals break up strong waves, safeguarding
low-lying land from destruction.
Especially vital as global warming fuels storms
that are more and more powerful.
The services that reefs provide are under threat from more than just global warming.
Local impacts – whether that's pollution,
unsustainable tourism or overfishing –
are adding to their woes.
Over half of the world's reefs have been lost in just a few decades.
If we continue like this, these beautiful underwater worlds will soon be lost.
Forever.
"My son is four, as I told you.
It's possible that his kids may never see a coral reef.
It really scares me to think of a world without coral reefs."
But luckily that's not the end of the story.
Sherry Constantine is a scientist and conservationist,
who's doing everything she can to help coral reefs.
"I live, I breathe, I sleep corals and coral reefs, and the environment, and the importance of it."
Sherry has established a large-scale conservation project in the Eastern Caribbean.
The goal was to find a balance.
Protecting corals and other ecosystems,
while still enabling tourism and fishing,
for example, in specific areas.
"The fact that the community was so involved
in the designation, the design of these areas;
that is why it was so successful."
There are also plenty of ways to enhance conservation efforts like these.
Take playing underwater sounds to lure back fish, for one slightly surprising example.
And there is evidence that by protecting reefs from local stresses,
Marine Protected Areas build resilience in the face of ocean acidification
and rising temperatures.
"So they're vitally important.
But what they don't do is prevent the waters from warming,
so we have to have multiple strategies in addition to Marine Protected Areas."
This is Lizzie McLeod, who's Global Coral Reefs Lead
at The Nature Conservancy.
Researchers, like Lizzie, are going one step further in the quest to help reefs
resist climate change, by investigating how to actually toughen coral reefs up.
"And so some of the strategies people are using is,
are taking corals that are 'stress hardened',
so they’re better able to deal with ocean warming.
And actually transplanting them, moving them from those areas to other areas,
with the hope that they'll pass along that trait to their offspring
and help the corals in that new area be better able to cope with warming."
One way of doing this is to find naturally heat-resistant corals
that have survived hot waters before,
and transplant them from one reef to another.
And these aren't the only cutting-edge techniques researchers are using.
Other teams are hoping to not just toughen up coral reefs as a whole –
but also the individual corals themselves.
"In my research, we are mostly focusing on increasing the
tolerance of corals to heat."
This is ecological geneticist Madeleine van Oppen.
Madeleine's looking at a range of approaches to make corals
more resistant to rising temperatures.
For example, selectively breeding
to toughen up the polyp animals.
Or, alternatively, tinkering with the algae
that give coral their colors.
"The microalgae that live inside the coral tissues, we can take them
out of the coral and most of these can be cultured in the lab.
And in the lab we can increase the rate by which these algae evolve."
Madeleine used this approach to create heat resistant algae –
which, when put back in polyps, created more heat-resistant corals.
In recent years, more and more researchers
have been coming together to help protect coral reefs.
So if we combine all these approaches,
is that it?
Will we be able to save these unique ecosystems
from climate change?
"If we implemented every tool in our toolbox today,
from Marine Protected Areas, reducing pollution,
using some of these more active interventions –
stress-hardening or manipulating the genetics of corals –
it will not be enough to save coral reefs, if we do not reduce emissions.
That is absolutely central."
The truth is that coral reefs are incredibly sensitive to warming waters.
In 2018, the Intergovernmental Panel on Climate Change warned
that even if the world limits global warming to 1.5 degrees,
coral reefs could decline by 90%.
If temperatures increase by 2 degrees, that figure is 99%...
or higher!
But the world could heat up by more than even this,
given our emissions path.
If we don't fight to stop climate change, the fight to save coral reefs is doomed.
Not in the distant future, but within just a few decades.
Coral reefs could be the first ecosystem entirely lost to the climate crisis.
"I think we clearly have not done enough.
I mean, we're sitting here now trying to get governments
and support governments, to make ambitious commitments
to reduce their global emissions.
More work needs to be done."
So saving coral reefs isn't a case of either-or.
Working with reefs might buy us some time, but climate action is essential.
Our environmental decisions around the world – whether that's reducing plastic use or limiting global
warming – could make all the difference for the future of the world's reefs.
"If you want to find out more about the environmental actions we can take around the world
to help protect coral reefs, then you're in the right place.
So check out our videos on everything from plastics to power plants,
and make sure you're subscribed.
We have new videos out every Friday."