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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