Climate Change


Climate Podcast: Trees matter. But just how much?

This week we’re talking trees, from Kew Gardens to Dame Judi Dench’s back garden. Join hosts Matt Winning and Mark Maslin as they chat to Prof Mat Disney about measuring trees, and to Craig Bennett, CEO of Wildlife Trusts about the importance of biodiversity, and how the UK is ‘beaver ready’. Listen now to hear about a NASA app that allows you to measure trees around you and assess how much carbon they can hold. We also chat about the UK climate, how wildlife is on a decline and what needs to be done now to undo the damage.


UCL Minds  0:01   

We are the first generation to feel the impact of climate change and the last generation that can do something about it. 


Mat Disney  0:09   

People love a headline, people want to sell the bullet for climate change. And it you know, there isn't one really other than decarbonizing the economy. 


Mark Maslin  0:18   

So if you think about a trillion trees that is the same land area as the whole the United States of America, 


Craig Bennett  0:24   

and the Wildlife Trust, we are beaver ready, and we don't need Michael Gove for that one. 


Matt Winning  0:32   

Hi there, and welcome to the podcast generation one. I'm Matt Winning this week, we're talking trees. Trees are often hailed as a bit of a climate crisis hero - plant more trees. And companies jump on this bandwagon. And they say for every coffee bought, we all plant a tree. But what does this mean for the climate and the climate crisis? What is the impact of more trees? And the most important single question for today's episode? Why do trees matter? 


UCL Minds  1:02   

You're listening to UCL generation one, turning science and ideas into climate action. 


Matt Winning  1:12   

I am joined with Mark Maslin again, with Mark Maslin and by Mark Maslin, I don't know what the correct term is. 


Mark Maslin  1:17   

I'm just here. Okay, man, I exist. I am therefore I am part you just yet your wonderful ecology called our podcast. There's this whole thing about trees, which is there's this paper that was published a couple of years ago, we should actually plant a trillion trees. Yeah. So if you think about a trillion trees, that is the same land area as the whole the United States of America. Yeah, it's a big undertaking. And even Donald Trump got on got with this idea and said, yes, it's a good idea to plant a trillion trees. And they said, Well, this was solved climate change. They sort of forgot, even if you did that, that would take out perhaps five years of our pollution. So it really doesn't solve climate change. It helps you and actually, it's something positive if you do it in the right place. But it's, you know, it's not going to be the great solution.  


Matt Winning  1:33   

So it's not the silver bullet in terms of solving climate change. Okay, well as introduce our guest for today. That is Matt Disney, who's a professor of remote sensing in the Department of Geography at University College London. Matt, welcome.  


Mat Disney  2:21   

Thank you very much. Nice to be here. 


Matt Winning  2:23   

Not at all I'm interested to hear about basically, you seem to be using technology to look at trees. 


Mat Disney  2:28   

Yes, that's right. So I you know, my title remote sensing. So that's looking at the Earth's surface, using satellites and aircraft and any bits of kit that we can get our hands on, that gives us a better picture of what's happening. And I've been particularly interested in trees and forests over the last five or 10 years. And what I've really been doing is using kind of high resolution, three dimensional mapping techniques that fire out millions of laser beams a second from an instrument on a tripod, and build up a three dimensional picture of trees and forests. And we've been dragging this kind of equipment through tropical forests over the last few years, to build up these very, very detailed three dimensional pictures of trees, which help us understand the relationship between their structure, how much carbon they store, right? And of course, then that's the link to climate.  


Matt Winning  3:16   

So yeah, obviously, if anyone doesn't know their trees, spray important soak up carbon, kind of store it, keep it safe for a bit,  


Mat Disney  3:24   

depending on what happens to them.  


Matt Winning  3:25   

Exactly. Yep. Depending if they're still still there. That sounds, first of all fascinating. And you're basically just creating cool maps of trees. 


Mat Disney  3:36   

Well, that's, you know, that's one aspect of it that is, that's very kind of eye catching, is that we build these kind of three dimensional pictures of the trees are very striking. And but it enables us to kind of measure the size and volume and structure of trees in a way that basically hasn't been possible to do before.  


Matt Winning  3:54   

You don't want to cut them open, 


Mat Disney  3:55   

You don't want to cut them down. Well, first question is, how do you weigh the tropical forests? Yeah. So there's a kind of question that, you know, sort of occurring to me is, how do you how do you even weigh a tree? Because you don't want to do that one at a time? Well, sometimes you have to, and the only way to do it for real is to cut it down to cut it into chunks, right to dry those chunks out to get rid of the water. Yeah. And then whatever you've got left to kind of the dried bit of wood, about half of that is carbon. And so to do that, if even a small trees is, you know, is hard work, tedious. It's expensive, and the trees gone. And it's gone. Yeah. So if you think about that, for a 50-60 metre tropical giant in the middle of you know, Borneo, or the Congo Basin, obviously, you don't want to cut them down. So, you know, the methods that we've been developing is a kind of alternative to that. 


Mark Maslin  4:41   

So So Matt, I mean, this is what I love about science because we'll each other's groupies because your stuff is just so amazing. But can you explain to the listeners, how do the lasers actually give you a picture? I mean, sort of like how do you actually get this sort of picture of the actual trees?  


Matt Winning  4:56   

Okay, so you've got basically an instrument sitting on a tripod which fires is out pulses of laser light several 100,000 times a second. And those laser beams have a range of up to about a kilometre. So they're in the near infrared, so you can't see them. And they speed out at the speed of light into the forest. And if they hit something, then some of that energy is returned back to the instrument it records and it says, Okay, this pulse hits something at this XYZ location, you know, 77 metres away. So it's a point. And so if we do that 100s of 1000s of times a second, we build up millions of points that tell us where there is stuff in in the area around us in the volume around us. Then you find out things like you know, a big tropical tree can have 10-15 kilometres of branches in it once you laid them out end to end. You know, these branches can we found a tree that we scanned in Kew Gardens, for example, a big chestnut tree there had 28 kilometres of branches. Amazing number 


Mark Maslin  5:55   

So didn't you do somebody famous? Didn't you have an oak tree? And I have to say the results from that just blew my mind. 


Matt Winning  6:03   

Yes. So we we got asked by the BBC to go and scan Dame Judi Dench's back garden. And I've had more communication and kudos for doing that than anything else I'll ever do in my career. That was a that was very entertaining because she was great to work with a really good sport and fascinated by the science that came out of it.  


I was hoping for a story like that.  


Mat Disney  6:26   

celebrity trees as a TV show. 


Mark Maslin  6:30   

But Matt, don't worry now after this podcast, they'll just be Yeah, they'll be talking about the podcast. Yeah, Dame Judi Dench, nothing to our podcast. So what was the outcome of that tree because I mean, it was really quite old oak tree and I was quite amazed by the size of it as well. 


Matt Winning  6:48   

So that tree is about 200 years old. So in terms of oaks, it's a good you know, early middle age, about the same as me, you know, strong early middle age. But there are trees or oak trees around in Britain that are estimated to be over 1000 years old and places like Windsor, great park and in Savernake forest, that are mostly huge and hollow and there's very little foliage left growing, but the trees are still alive. They're still growing, but because they're hollow, they're essentially impossible to age. Dame Judy's tree was about 25 tonnes of carbon, and it had about 18 kilometres of branches in it. So she was kind of blown away when we were given those figures. But you know, to put that into context, like I say, a big, tropical hardwood, we were measured the tallest tree, quote, unquote, in the tropics, possibly the tallest flowering plants in the world. There's an angiosperm tree in Southeast Asia, which was just over 100 metres tall and weighed 80 tonnes. 


Mark Maslin  7:53   

What about the argument that we should be planting a trillion trees? Your your technology can actually tell us where they're being planted? How much carbon they're storing? I mean, is this a good idea? 


Matt Winning  8:04   

Well, going back to what we're finding with our, you know, our measurements of carbon in trees and forests, first of all, bottom line is were showing that the current estimates seem to be an underestimate of how much carbon is stored in trees and forests. And that's because in order to do you know, doing one tree or 100 trees, or 1000 trees is all very well, but you need to extrapolate across the whole of the tropics, 3 trillion trees. And in order to do that, you need simplified models, you need satellite estimates. And the models that are used currently to generate those estimates of how much carbon is in tropical forests, we think are fair under our estimate, planting trees, this idea of a trillion trees that you know, that might, you know, you brought up, it's, it's one that very much catches people's attention. It's, you know, people have a catchy number. People love a headline, people want a silver bullet for climate change. And it you know, there isn't one really other than decarbonizing the economy. So, that's the silver bullet. But that's the one that people don't really want to hear. You plant loads of trees in places where maybe, let's think about Northern China where there's huge afforestation programmes going on, which in general is there to do things like protecting hydrological systems and preventing you know, flash flooding and runoff. Good thing. From a climate perspective, those trees are actually quite dark in colour compared to the background so they actually absorb more sunlight. So the surface actually gets warmer than it would have done if you left it with no trees and snow cover in the winter. Because it changes what we call the albedo reflectivity of the surface. And when you do that, on a very large scale, you suddenly have impacts on you know, heating up the surface, which are unintended consequences, you're actually making things warmer, which evaporates more water which affects the hydrological cycle and and on you go you didn't think of that 


Yeah, sounds like an incredibly complex system and if throwing trees down really shouldn't be fuel on the fire, but it's potential fuel. 


Mat Disney  10:02   

So, you know, thinking about the idea of planting trees and you know, coming back to I do some work quite a lot of work on urban forests, you know, people want what is an urban forest. And you know, London is a great example London, there are 9 million trees in London, there are more trees and people, there are parts of London, we did some work showing that the amount of carbon stored per hectare in places like Highgate Cemetery, are equivalent to the carbon stored in tropical rainforest. Wow. Because there are big old trees that have been left untouched to grow for several 100 years. And they're, you know, they're very beautiful. And they're kind of, you know, they're easy to leave there because no one wants to come in and cut trees down in a cemetery. So trees in cities are incredibly important. We all know that moderate temperature, and we just like having them around. And there are definite health benefits to having trees, protecting trees that we have already large old tree, London's full of them. Yeah, but there's this race to plant more trees. But where do you put them? The mortality rate is about 95%. Oh, wow. So you plant the tree, and in 20 years, it probably won't be there. And it's 20 years to 30 years is when it starts to really give you those benefits back. 


Matt Winning  11:10   

Yeah. Yeah. I mean, it's so much again, to myself, you know, didn't do much for the first 30 years of my life. And now,  


Mat Disney  11:16   

just coming into your prime,  


Matt Winning  11:17   

yeah, me and Jesus. 


Mark Maslin  11:20   

So Matt, if, if you had a magic wand, and based on all the incredible science you're doing, where would you plant trees? If you were in control, you are making policy? What should we do? 


Mat Disney  11:32   

One of the first things I do is is, you know, it's actually one of the things I'm trying to do at the moment is looking at what we have already, because that's one of the things that is actually done. There's, there's, there's a race to see, why should we plant more trees. And there are lots of spaces, there are lots of brownfield sites, I was just thinking about the UK, there's lots of brownfield sites, there are lots of areas of urban development where there are rules about you know, what you have to do in terms of planting trees and providing access to green space. But the rules are very easy to get around, and they're very easy to gain is perhaps the wrong word. But you can plant lots of small trees. And then if there's no requirement for you to look after them, after five years, after five years, they'll be gone. Yeah. So Glasgow at the moment, and Belfast are planting a million trees. Again, a big number that's easy to communicate. In Belfast, they don't know where they're going to plant them. In Glasgow, there are there are areas where they're going to plant and there's no real then, okay, well, we're going to plant those trees and ensure that they survive at a rate of 50%. For 25 years. People want to see, yeah, photo op, planting, you know, hey,  


Matt Winning  11:33   

the fun bit  


Mat Disney  12:02   

the fun bit, aren't people don't want to come back every year and go, Okay, well, what's happened? And what's happening here? And how long is this going to live? For?  


Matt Winning  12:51   

Are you going to sell this technology and give it to everbody?  


Mat Disney  12:53   

No, not something I'm going to, you know, we're gonna make sure that it's out there, open access science, that's what it's all about. But you know that, you know, we're developing tools using things like Google Earth Engine, where you can already do a far better job than is being done currently about assessing what we have in cities in the UK. So, you know, we've got data now that will allow us to do that from aircraft and from space. So why aren't we using it to inform policy better, because it's really easy to do? 


Matt Winning  13:19   

That was absolutely fascinating. And I feel like I've learned a huge amount about trees. And as you say, you know, protect the ones we already have, what ones are already doing well, and then the ones that you do plant, look after them for a long time, I think sounds excellent. And hopefully one day we'll all have a scanner going around, scanning around what we do. 


Mat Disney  13:37   

You know, the space station flying over at the moment, it's got a big laser on board that's measuring trees and forests are called Jedi. Of course, it is it's a NASA instrument. 


Mark Maslin  13:44   

Ah, I'm sorry that's brilliant  


Mat Disney  13:47   

ecosystem dynamics investigate just a little plot. I've worked with the Jedi team. And you know, they've milked that for all it's a bit yeah, 


Matt Winning  13:54   

of course they have to. 


Mark Maslin  13:55   

I was gonna say, can you imagine linking Jedi to your mobile phone? So you could actually see 


Mat Disney  14:00   

there is trees there is already in Sri, ah, that does this kind of  


Matt Winning  14:03   

there's an app.  


Mat Disney  14:04   

Yeah. Oh, what a NASA app that looks at, you know, tree size. And you know, can you estimate how much carbon is in your tree?  


Matt Winning  14:11   

Brilliant. Well, thanks so much for joining us today. 


Unknown Speaker  14:14   

No problem. And I always like to talk about trees. 


Matt Winning  14:17   

I mean, a query and also, I know realise that I like to listen to people to talking about trees. So fantastic. So, Mat, we are asking our guests, if you could keep one thing that we need in 30 years time to help climate change, what would it be? Or if you could get rid of one thing that would no longer exist in 30 years time? What would that be or create something new 


Unknown Speaker  14:39   

keep things is the whole bounce of tropical rainforest?  


Matt Winning  14:42   

Yes great answer. I mean, fairly sensible. Done.  


Mat Disney  14:46   

We're gonna need a fairly large container. 


Matt Winning  14:48   

Yeah, we're gonna need somewhere to put it. 


UCL Minds  14:52   

To download the NASA app and try weighing trees yourself, visit ucl.ac.uk/generation- one. 


Matt Winning  15:04   

Okay, so our second guest for today is Craig Bennett, who is the CEO of the wildlife trusts and used to attend UCL. So we'll talk about what the the trust's mission is, and why the work matters. Hello, Craig.  


Craig Bennett  15:18   

Hello there.  


Matt Winning  15:19   

Lovely to speak to you. What did you What did you do at UCL? 


Craig Bennett  15:22   

I did the MSc in conservation, nature conservation, which at the time was a sort of a joint initiative between the Department of Biology and Department of Geography. And I, I loved it 


Matt Winning  15:32   

That sounds like an interesting course. And also you've gone on to clearly use your degree, which is wonderful to hear, essentially, yeah, what is the mission of the Wildlife Trust? What what do you spend your time doing? 


Craig Bennett  15:45   

Well very simply it's to bring nature back, bring wildlife back. But I think, given the science we've seen over the emerge over the last few decades, and you know, that phrase that we've heard time and again, that we're facing a climate and ecological emergency, and the science really does back it up. Our mission now is simply that that nature is being used to overcome those climate and nature emergencies, and that by 2030, that we are very clearly on the journey to having turned, turned the corner on those and make sure that all those trends we've seen of declining animal populations of parts per million of carbon in the atmosphere going up, actually, we've turned those around by 2013. They're starting to head in the right direction. 


Matt Winning  16:29   

You touched there on how things have been declining, how things are getting worse. Let's start with the kind of bad news first, How bad has it got or on how bad may get?  


Craig Bennett  16:39   

Well there's different ways of looking at it, here in the UK the statistic I quote time and again, is that 41% of our wildlife species have declined in abundance since the early 1970s. So roughly in my lifetime, 41% wildlife species are poor and thinner, if you like than they once were in terms of number of those individuals. We've seen increased fragmentation of wildlife habitats. And basically nature's not just not working the way it should be. We do not have the functioning ecosystems in this country that we really should have. Just in the last couple of weeks, we saw a report by the Natural History Museum, saying that the UK is one of the most nature depleted countries anywhere in the world. I think scientists have been warning us about it for decades. I remember two, three decades ago, the first time I came across the the argument that if we continue to fragment wildlife habitats, particular tropics, that that would lead to the emergence of more and more pandemics. And so we've seen that with Ebola with SARS, of course, back to HIV in the 1980s. And of course, most recently, I think almost certainly will end up being proved that COVID was caused as a zoonotic escape from wildlife populations into humans, because very simply, we're not making enough space for nature. 


Matt Winning  17:54   

Yeah, I think that's a really interesting point. Actually, as you see, I think a lot of people, especially in the West, perhaps felt like they were maybe insulated from things like this. How much worse could it get? If we if we sort of continue on this path? 


Unknown Speaker  18:09   

Well, I mean, we are still seeing those wildlife declines, we're still seeing fragmentation of wildlife habitat. But what's so frustrating about that is we know what we need to do to turn that around. I mean, globally, it's sort of been setting out a target of trying to get 30% of our land and sea into recovery for nature, by 2030. And that is the sort of bare essentials that we need to kind of turn this around is the kind of equivalent in biodiversity terms, if you like, of the 1.5 degree temperature goal in around the climate talks. We've needed that for biodiversity for a long time, something to focus on. And, you know, yes, there's sort of scientific underpinning as to why that's necessary. Yes, it's roughly around at least a third of our land and see if it can be managed primarily for nature, and to let nature thrive, and then that would provide the foundation for nature's recovery. But as ever, with these things like the 1.5 degree target, 30% target, these are sort of a mishmash of scientific targets and political target, something that people can agree on, and kind of focus on. And the problem about this is, is that the change that you see environmental change is not linear. The real concern that we have at the moment is that you can push, for example, on climate into a different state where you see positive feedback loops in the Earth system positive in this case is not good. What it means is you get this mutually reinforcing cycle in the Earth's climate system or in nature, where because as humans, we've tipped things to a certain point, then it sort of moves into a new state, and it's very hard to get back from there. We move into runaway climate change, for example. So we really have to act immediately. And if we could wave a magic wand and solve this tonight, that would be the thing to do. So but instead, what we have to do, is we have to really, really determine that we're gonna we're gonna to make a big difference by 2013 Put all the efforts into turning around the climate ecological crisis in the next 10 years. 


Matt Winning  20:06   

Yes, super point there about the kind of complexity of all this as well. So what would be in terms of protecting land and sea by 2030? What are the sorts of things that need to be implemented there? What are the actions that need to be taken at a kind of high level, 


Craig Bennett  20:23   

I mean, it varies from country to country but but take the UK as an example, there's broadly three things we need to do. The first is we need to make more space for nature. So that does mean that we need to get as I said, around 30% of our land and sea being managed for nature. And at the moment, actually, we've only got around 5%, that is actually in good condition. So we've got a long way to go over the next nine years to get to 30%. That means we need to get our current designated sites, our sites of special scientific interest in good condition. And you know, half of them are not at the moment. And national parks and our areas of outstanding natural beauty or landscape designations. They're not actually primarily wildlife designations, but manage them in a wild way would help. At the moment, sometimes our wildlife is in a worse condition inside our national parks and outside them. But it's not just the quantity of land we're talking about. It's actually the connections between them as well. So good wildlife corridors, linking up current reserves and designated sites out in the countryside, including part of agriculture, let's move to from intensive agriculture to regenerative agriculture, where there's more space for nature, and we have those field boundaries that could produce a nature recovery network.  


Craig Bennett 21:38   

The second thing we need to do is restore the abundance of nature. So not just a space, but the abundance of our wildlife populations. You know, I was saying before how 41% of our wildlife species have declined in abundance in the last 40-50 years, including, for example, some of our bee populations. A lot of that is associated with use of pesticides. So we absolutely need to be cutting the amount of pesticides we use, create more habitat for wildlife populations, and restore the abundance. But we also need to get nature working again. For example, our wetlands need to be wet. As simple as that. And at the moment, many of our chalk streams run dry. We need to reintroduce species that are missing like beavers. So for example, beavers are very good at holding water back into their landscape and being those ecosystem engineers that make sure our wetlands are wet. Those are just some examples of what we need to be doing there to get nature working again. 


Matt Winning  22:28   

I do remember a couple years ago when Michael Gove was the Environment Secretary, I think he released a pair of beavers back into the Forest of Dean. Do we need Michael Gove to go around the country just sort of throwing beavers in all the rivers? 


Craig Bennett 22:44   

Well, the Wildlife Trusts we have a beavers in enclosures right across the country at the moment, waiting for the permissions from Defra to allow us to have free roaming beavers at the moment it is actually against the law to release beavers into the wild. Can you believe! There is a consultation going on right now? Thankfully, about by Defra to say yes, beavers can be released in the wild and have wild roaming beavers. At the Wildlife Trust we are beaver ready! We're absolutely ready with these beavers in our enclosures ready for right across the country.  


Matt Winning  23:18   

Yeah, yeah, yeah 


Craig Bennett 23:19   

We don't need Michael Gove for that one, we just need to be told by Defra, hopefully in the new year that we can take down those fences and have beavers returning to British ecosystems. And to put it clear, you know, there's sometimes a debate about reintroducing these species. They are just as British as Shakespeare or just as British as Yorkshire pudding or anything else you might like to choose. It is just a scandal that they've been missing from our ecosystems 


Matt Winning  23:45   

Release the Beavers, I'll wait for wait for that to be shouted from the rooftops. So thank you so much for joining us. Craig really appreciated, chatting with you, we've got a question that we've been asking our guests, which is just about thinking about a time capsule related to climate change. So So is there something that you would like to get rid off over that you know, something that doesn't exist in 30 years time or something that you would like to sort of keep in see 30 years time? Or is there something we you know, we could create something brand new, 


Craig Bennett  24:14   

we're like the obvious thing to get rid of and you were talking before about how climate change climate ecological emergency can be really complicated. That's true. But also on one level, it's really simple, on climate change, you solve climate change, if you stop using fossil fuels, it's as simple as that really. It would be an oil barrel that I would put in that time capsule to get rid of. And that could be really clear. 


Matt Winning  24:35   

I like that. I like that you've put it you know, a barrel of oil in there, which is essentially all sorts of wildlife but for a long, long time ago, 


Craig Bennett  24:44   

Let's keep fossilised biodiversity fossilised. 


UCL Minds  24:49   

You're listening to UCL generation one, turning science and ideas into climate action. 


Matt Winning  25:01   

Well, that was Craig Bennett, the CEO of The Wildlife Trusts talking about wildlife, protecting it and the fact that they are beaver ready. Up next Mark Maslin is going to round up the week's news stories that he thinks you should know about climate change. I might not even be news stories and maybe, you know, gossip columns. It could be heat magazine is about heat, I think now, I don't know. Anyway, point is Marks up next. 


I've been Matt winning. And that's it from this episode of Generation One from University College London, turning climate science into action. If you'd like to ask a question or suggest a guest, or leave us a voice note in an email that you would like to hear, then you can do that at podcasts@ucl.ac.uk. Otherwise, for more information about UCL's work in the climate space, and what our staff and students as well as our researchers are doing to make sure that we don't just talk the talk but actually walk the walk to a more sustainable future, head over to UCL Generation One website, or use the hashtag UCL Generation One