Coral reefs cross survival threshold in Earth’s first major climate tipping point

FRANCE 24 English

FRANCE 24's Sharon Gaffney speaks with Professor Tim Lenton, founding director of the Global Systems Institute at the University of Exeter, and lead author of the Global Tipping Points report, which has revealed that the world’s coral reefs now in an almost irreversible die-off, marking what scientists describe as the first “tipping point” in climate-driven ecosystem collapse.  Visit our website: http://www.france24.com  Like us on Facebook: https://www.facebook.com/FRANCE24.English  Follow us on Twitter: https://twitter.com/France24_en

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00:00This is Apropos.

00:04The planet's tropical coral reefs have almost certainly crossed a point of no return.

00:10That's according to a major new report from scientists and conservationists who are warning

00:15that global warming is passing dangerous thresholds sooner than expected

00:20and that the world's coral reefs are now in an almost irreversible state of decline.

00:26Yinka Oyotade has the details.

00:31Oases of life and colour right in the middle of the ocean.

00:36Coral reefs are a haven for marine life and divers alike.

00:40But this underwater paradise is fragile and under threat from climate change.

00:45When the water gets too warm, corals bleach and die.

00:50Now a new study released on Monday warns that humans have already caused so much global warming

00:55the damage to reefs may go beyond repair, suggesting we may have passed a tipping point.

01:02A disaster for marine life.

01:06There are countless species of corals with different shapes

01:10and all these shapes create ecological niches where certain fish species can hide from predators

01:15or find a place to live.

01:16This rich underwater world supports incredible biodiversity.

01:23Up to 30% of all known marine species rely on coral reefs at some point in their life cycle,

01:30especially fish.

01:31Millions of people who rely on fishing could lose their livelihoods,

01:36particularly in Southeast Asia, where coral reefs are widespread.

01:41But they offer more than just food.

01:43They also break waves, helping to reduce storm damage.

01:47Without them, many coastal areas face erosion and flooding.

01:50Today, 500 million people depend on coral reefs for food and protection from the ocean.

01:58For more, let's bring in the lead author of this report, Tim Lenton,

02:03who is also the founding director of the Global Systems Institute.

02:07Great to have you with us on the programme this evening, Tim.

02:10So the Earth has reached its first catastrophic climate tipping point.

02:15What exactly does that mean?

02:17And talk us through how exactly you and your fellow researchers came to this conclusion.

02:23Well, as that lovely report showed, it means that change, in this case,

02:28in this incredible ecosystem, is now happening in a self-propelling way in a bad direction.

02:36And that's the nature of tipping point change.

02:39If you want to think about a familiar example, when you lean back on a chair,

02:45you know that there's a balance point where a small nudge can create a self-propelling change of you

02:50and the chair into a very different, stable state.

02:54That's suddenly what's happening to the coral reefs,

02:56and it's what's happening or what's at risk of happening for many other critical parts of our life support system.

03:03The way we could tell that this was the case for coral reefs is just in the last couple of years,

03:10we've been experiencing unusual warmth at a planetary scale,

03:15but also heat waves in the ocean, in the tropics,

03:18that have taken the global temperature above one and a half degrees centigrade,

03:23above the pre-industrial level,

03:24where we'd already estimated the corals would pass their tipping point.

03:28And sure enough, over 80% of them have been experiencing these extreme bleaching events and dieback,

03:36rather confirming the prediction.

03:39And at the same time, it's become clear that the world is going to carry on warming,

03:45and what has been a temporary experience of one and a half degrees of warming

03:48is, I'm afraid, going to become, that's going to be the average temperature within a few years, probably,

03:56and we're going to carry on above that.

03:58So that's why we can say the reefs are now at risk of large-scale irreversible decline.

04:05It's not a case of all hope is lost,

04:07but it does mean we need to focus on those crucial reef ecosystems on the cooler end of the range

04:13that we can still perhaps preserve or protect,

04:16and reduce the other pressure on those reefs like overfishing and pollution

04:20to give them some resilience.

04:23And then in the big picture, we've got to call eventually the climate back down again

04:27if we want this incredible ecosystem to be the flourishing, familiar thing it's always been.

04:32So not to give up hope entirely is what you're saying, though.

04:36Is it inevitable, though, do you think, realistically speaking,

04:40that perhaps not within the next few years, but they will eventually perish, these coral reefs?

04:45Or can something realistically be done to reverse this damage and to restore them?

04:52Well, I fear that many of them are at risk of being lost,

04:59but a fraction could still be preserved, and we should work to preserve that fraction.

05:05And many coral reef conservationists are already trying to do that.

05:09So, as I've emphasised, it's kind of crucial to reduce all of the different human drivers on the reefs,

05:15to give them, the ones that have a chance of survival, the best chance, the most resilience.

05:21But there's innovations going on.

05:22People are experimenting with trying to breed strains of coral that are more tolerant of the warm conditions.

05:29Over the Great Barrier Reef, there's even efforts to seed the air with sea salt that will make the clouds brighter,

05:38that will create a kind of sunshade or better cooling effect over the reefs.

05:44I think we have to think in those terms of what can we best do to support the resilience of some reefs,

05:51to give a chance that in the future, if we eventually cool the climate back down again,

05:56they have a chance to, should we say, recolonise.

06:00But then the crucial message there is that we have to limit,

06:03we have to stop global warming first and then begin to reverse it.

06:08And that's why our report also emphasises the potential to trigger what we call positive tipping points,

06:14where we can accelerate the change we need to zero emissions, technologies and behaviours.

06:20And just tell us, why are coral reefs themselves so vulnerable?

06:25And what kind of impact does it have when they're starting to perish on the wider ecosystem,

06:31also on the people who live close to coasts right around the world,

06:34particularly in these more tropical, these warmer regions?

06:37Yeah, so one reason that they're vulnerable is a coral reef is already an amazing partnership,

06:48or symbiosis we call it, between the coral, which is actually an animal,

06:52and some photosynthesising algae that kind of live in partnership with it.

06:56But that seems to be quite a sensitive relationship.

07:00So when it gets too hot, the corals will reject their algal partners.

07:04Because in the bigger level of the ecosystem, coral reefs are actually living in kind of nutrient deserts in the ocean.

07:11And yet, as we can all see from the pictures, they're this abundance of life.

07:15And the only way they can support that flourishing and abundance is because they're brilliant at cycling

07:20all the nutrients and resources they need within the system.

07:25And it's not just the corals and the algae that play a part in that.

07:27It's the sponges, it's the reef fish, it's all the amazing panoply that we see as colourful life.

07:34But when you start to break down those recycling loops,

07:39the system can switch into another state where these bleached-out corals have rejected their algae,

07:47these tiny algae that their partners.

07:48Unfortunately, instead, the system gets colonised by bigger algae, seaweed, we'd think of it,

07:53that can cloak the coral, make a much less diverse system.

07:58And that makes it hard or very difficult for the original coral ecosystem and all those partnerships to recolonise.

08:08So that's a little bit about why you have a system which is vulnerable when its natural cycles get broken down.

08:17And, yeah, in terms of the bigger picture of why is this so important,

08:23well, it's all of that amazing cycling of resources that makes them so abundant with life,

08:29including fish that provide abundant fisheries for many, many people.

08:35And as the opening report showed, at the same time,

08:38the coral is this kind of self-regulating system that has grown up if the sea levels have risen over thousands of years since the last ice age

08:49and presents this natural barrier to the incoming tide and the waves.

08:53But unfortunately, when you lose the reef and the system starts to degrade,

08:58that can literally break up and we'll lose,

09:01or the communities behind those reefs will lose their shoreline protection.

09:05So these things add up in terms of what we call ecosystem services they provide.

09:12And recent estimates will say that the total value of all of this,

09:18the human value of these ecosystems, could be of the order of $2 trillion per year,

09:25which is phenomenal.

09:27So there's a lot at stake, you could say, in an economic sense as well as in an ecological sense.

09:33And Tim, your report also refers to this being the first catastrophic climate tipping point.

09:39You are concerned that others are approaching.

09:41The report also is coming just ahead of the COP30 climate change conference,

09:46which is going to be taking place in Brazil, the Amazon being a real concern as well, isn't it?

09:52It is, because just in the last couple of years,

09:55new research has shown that the Amazon that we knew was at possible risk of its own dieback

10:02is now at greater risk than we thought because of the combined effects of not just climate change,

10:09which is causing some extraordinary droughts and fires that start to destroy parts of the forest,

10:16but also people are still directly chopping it down.

10:20And unfortunately, in the last year or so, deforestation rates have shot up again.

10:24And together, that direct human pressure and then the wider pressure of climate change

10:29means that the Amazon could be at risk of a tipping point below two degrees centigrade of global warming.

10:35So we'll be getting into the danger zone of one and a half to two degrees centigrade of global warming,

10:40probably, unfortunately, entering the danger zone after 2030.

10:44And that's kind of iconic when the COP30 meeting is happening in the Amazon.

10:48And, of course, the Brazilian presidency is very aware of that

10:53and also very committed to wanting to create, to mobilise global action

11:00to try and protect this critical ecosystem both ways.

11:04They've got to reduce the largely illegal destruction of the forest,

11:09but they need all of us getting on board with accelerated climate action to limit global warming.

11:15Tim Lenton, the lead author of that Global Tipping Points report.

11:19Thanks so much for being with us on the programme this evening.

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