So please help me welcome Professor Helen Chesky Thank you, Christine. And hello everyone. It's great to see you here. And isn't it nice that spring is coming? We like spring is coming because all the life is coming back. So you might be wondering why it is that someone who's clearly a physicist who studies the ocean is about to give you a lecture on life and a living planet. And the reason is that I'm still not a biologist, but I do think that I spend a lot of my time thinking about the big picture of planet Earth. And I think it's something that we all need at the moment, which is part of what this lecture series is about. So instead of focusing in, although there will be some stories about individual animals, I'm going to look at the big picture. And I guess the biggest picture of all is Earth seen from space. So I thought it might be good to start with the perspective of a couple of people who have been there, who've looked at this view from above. And one of them is Bill Anders, who was on the Apollo missions. He is the one that took this photograph of Earth. And he says something which I think should be broadcast far more frequently when people talk about the Apollo missions. He said, We came all this way to explore the moon, and the most important thing that we've discovered is Earth. As though that was a surprise. I mean, I don't know what they were expecting. The moon's lovely. Any of you who've heard me ranting about the moon in the past will know this. The moon is very nice, but it's not nearly as interesting as Earth. And then the other quote came a little bit later from one of the other Apollo astronauts that that beautiful, warm, living object looked so fragile, so delicate that if you touched it with a finger, it would crumble and fall apart. Seeing this has to change a man, and indeed any person who's looking at it. And so here we are, we have the defining features of Earth. It's alive, it's doing something, it matters, it's complex and interesting. But what really sets Earth apart, as far as we know for definite the moment, we're sure there's life out there somewhere, probably, the chances of us finding it are quite low. That's a different lecture. But anyway, the point is that life matters very, very much for the way Earth is. And of course, today we have a much more detailed view of Earth than those Apollo astronauts did. So this is a composite of data taken from the PACE satellite, which has been collecting data for the past two years. So it's a relatively new satellite, it's got a focus on the colours that come away from the planet. And you can see this beautiful image, the whole thing, the big picture. And what I want to talk to you about this evening is how this is shaped by life. Because I don't just want to focus on life itself, but I want to focus on what life is doing. Because in the dynamic engine that is Earth, life is part of the process, right? It's not just sitting on top of this planet, it's actively shaping it and forming it, and the whole thing forms an engine together. This is not a physical engine that happens to have life living on top of it. Life is directly woven into the web. And I want to give you, just show you a sort of open a tiny window on all the complex ways that that can happen. And when we think about life on Earth, it tends to be like this, right? We've got lots of brightly coloured things and they're very exciting, and these are lovely animals. I want I should say at the start that although I'm going to talk about the functional things that life does, of course, it doesn't mean that I'm um diminishing in any way the uh beauty and intricacy and importance of all these individual animals, the species. I'm not going to be looking at them at that stage, but of course they are beautiful and interesting in their own right. I don't want to give you the impression that I think of animals purely in terms of their function in the world, but their function is really important. But one of the things that has happened, and we'll see as the lecture goes on, is that there's been no one really frames it like this, but you may have heard of the Copernican revolution a few centuries ago, where, you know, humans thought we were the center of the center of the universe, it all literally revolved around us, and then slowly we got taken away from the center of the universe as it turned out Earth went round the sun, and then there was quite a lot of the rest of the universe out there. And a similar thing is happening in biology. We think intuitively that the most important life is the life that is us or that we can pick up and see. But actually, the more we learn about life on Earth, the more we are not relegated to a corner, but we are definitely not the most important life on our planet. Although, as we'll see at the end, humans are making a sterling effort to put themselves back into the picture. So, where's this lecture going to go? I want to I want to cover three big topics here. One of them is just a sort of grand survey of life, the what, the where, and the when. And then I want to ask these questions about what it's all doing and give you some examples of what life is doing. And then I want to come at the end to the bit you all know is coming, which is how it's changing and how we think about that. Um, and this first section does involve a few statistics. And I apologize if you don't like uh plots, there are only a few, but I think they're really important because these are the this is the only way we can really get our heads inside what life on earth really is. So let's start with how much of it there is, and biologists being scientists like sort of weighing things. So let's look at the total biomass. So biomass is living stuff. Let's add up the total biomass on planet Earth and see what it looks like, see what we've got. And it looks like this. So this is from a very famous paper from 2018. And what you're looking at here in this square is all the mass of all types of life, and the area of each segment represents the mass of that type of life. So you can see that most life on planet Earth is plants. Very clearly, if you look at the whole big picture, this is a planet of plants. And then the next two things down there, so there's archaea and bacteria, which are different types of single-celled creatures, organisms. So they're they're single cells, they're very tiny. Viruses, we can have a debate about whether they're alive somewhere else. But anyway, there's there's quite uh, you know, a bit of mass that's viruses. Protists also single celled, fungi you know about, like there's they come in both big and small forms. Uh so that's most of life on Earth. And then down in the corner, in the bottom right-hand corner, in a tiny little triangle, that's where the animals are. But when we think about life, we tend to think about the animals. So let's have a look. If we just think about the animals, how how is all the biomass distributed? So here's the other half of that plot. We're going to take that triangle, we're going to expand it out to form another square. And what does this one look like? Uh well, actually, now we're mostly insects, so there's different types of arthropods, not all of them are insects, but there's a lot of insects when we come to animals. Uh, we can see mollusks and worms of various types at the top. These things in the bottom left are things like jellyfish. Um, and then there's this bottom right-hand corner here. And this is where it gets really interesting for us because, first of all, we can see that wild mammals, so that's what we think of when life on earth is presented to us in documentaries. We think it's tigers and rhinos and you know, mice and things. Tiny, tiny little fraction is wild mammals, used to be bigger. Um, humans are almost 10 times, our mass is almost 10 times that of wild mammals. So we are an incredibly significant, just mass of stuff on this planet. And even bigger than us is our livestock. Cows, pigs, sheep, all of that kind of thing. They are a really significant fraction of the large life on this planet. So you can see here again, mostly small things, fish obviously come in a range of sizes, but human the human influence world is all down here in the bottom right. And so we are a tiny fraction of a very complex world, even though we are growing at a possibly alarming rate. So then let's have a quick think about how big it is. This is just setting up what's going to come next. So this is a relatively simple plot. We've got body size along the bottom here on a log scale. So what that means is up the top. On the right hand side of the scale, 10,000 tons for a single organism. That's what's up there. Down the other end, you've got fractions of a picogram, which is very, very, very tiny. Uh, and if you're curious about what those two things are, this this thing here, that the small circle, not the big one, that's the smallest known living uh cell. It can actually only live when it's sort of stuck onto the side of this slightly bigger one. So you can argue about whether it's a single organism. But anyway, that's the smallest thing, 400 nanometers wide, and the largest known living single organism is a honey fungus, uh, which is underneath a forest in Oregon, and it kind of spread out under the forest, and it's all part, it's all connected, so it's considered to be a single organism. So that's how you get up to the 10,000 ton mark. But anyway, the point here is that when you look at all life on Earth, there's a decent chunk of it that's very small, there's a decent chunk of it which is quite big, and then there's stuff in the middle, but not an enormous amount of it. Um, but then when we come to trees, of course, quite a lot of a tree is not currently living. It has been, and now it's just structural support for the rest of it. So plants are kind of biased by all the woody stems and trunks and things that are just structural support. But anyway, big and small, this will become relevant later. Um, and then let's just take a quick look at where it's all living, because this is where it starts to get interesting and challenges the sort of our typical conceptions of what life is. So it's another box, but we'll get to the end of the plot soon. Um, another another um square here, and the light brown, that's everything that's kind of on land. Um, and then you can see there's a decent chunk in the bottom left-hand corner that's underneath, and that could be underneath sediments in the ocean, it could be in the soil, as we saw in the lecture on rocks and soil, and then there's that tiny fraction up there which is living in the ocean. Let's expand this out a little bit more to see what's living where. And the thing so what we've got here is a plot of for each group, we go from 0% to 100%, and then we can see where it's all living. And I want to draw your attention to the animals, where most of the animals are marine animals. But on the left-hand side plot, it looks like marine animals are a tiny fraction of everything that's going on. And those two things seem to contradict each other. And now I'm an oceanographer, I'm never going to say that what's in the ocean doesn't matter. But there's something weird, right? Life in the ocean is a relatively small fraction of the mass. Um, but then it does seem to include lots and lots of the animals. So this is a some data from that same satellite, the PACE satellites, showing where life is in the oceans. And this is just fabulous data. We've only had this data within the past two years. And if you look at the ocean here, you can see so the colours that are closer to reds and orange, that's where there's lots of life. You can see around the coasts, there's lots of life. And then the dark blues are where there are much, much lower abundances of life, and uh very little. When that's purple, it's almost basically a desert. So you can see that life is distributed throughout the ocean, and of course, the ocean is very, very, very big. So, how is it that life in it is so very, very, very small? So, let's just have a think about some comparisons between life on land and life in the ocean, because they start to challenge our assumptions. So, if we look at the total mass, so the important bits here, the number the numbers are in white, the bits in green are just the units, but the units are the same on both sides. So, as we've seen, there's much more mass of life on land than there is in the ocean. But then let's look at productivity, and what that means is the amount of uh sun harvesting that's going on, the amount of energy that's being harvested and turned into sugars, um, how does that compare? Well, it's almost equal on the land and the ocean. So, in spite of ocean life having a very tiny mass overall, actually it's almost as important in the total amount of productivity. And the reason that productivity matters is because everything else feeds off those sun harvesters. There's a small number of creatures that can photosynthesize, that can harvest the sun's energy, can package it up for everything else, and all other life relies on them. So it really matters. So here, the ocean is almost as important as the land. And then here's something else. If we look at the turnover time, how quickly are organisms coming and going in this system, we start to see part of the reason why. In on land, things tend to live a lot longer, whereas in the ocean, things are cycling around very, very, very quickly. And here, so here we start to see the fundamental difference between life on land and life in the ocean, which is that life on land is slow, it's stationary, and it lives a very, very, very long time. Whereas life in the ocean is very small, a lot of it is just single cells. Um, it's mobile, it's moving around all over the place, and it's living and dying and living and dying and living and dying really quickly. It's not storing very much. Whereas you can imagine all the biomass in a tree in the middle of a trunk, that's stored carbon, that's not going anywhere. There isn't really storage like that in life in the ocean, it's just turning over really, really, really quickly. So the first thing here is that it's clearly not the case that the amount of biomass there is is directly related to the function it's doing. Even a biomass that's quite small can be doing lots and lots and lots of useful things. But there's something else here, which is to do with the turnover time here. So the reason that the turnover time in the ocean is so short for an organism that's living, average organism that's living in the ocean, obviously you get things like blue whales that live longer, is that most of these are single cells. And really the story of Earth is the story of the single-celled organisms. We live in a microbial world, even though it doesn't necessarily look like it to our eyes. We're biased. So if you take a look at the genetics of all of life and you draw out the tree of life, then details on this don't really matter. But basically, what's going on is that if you start in the middle where all the bits join up, that's kind of an ancestor a long, long time ago, and every branch that's off it is sort of an evolutionary tree that comes off it. And you can see that a gigantic amount of the total diversity of life on Earth genetically comes in the bacteria, which is all the stuff around the top there. And then so that's all single cells. And then down here at the bottom we've got the archaea, which are also single cells but different to bacteria, and then a subset of the archaea is what's called the eukaryotes, and all multicellular life is contained in that little bit there. Um so all of this stuff and almost all of the diversity is in single cells. So microbes are like little factories, basically. They're busy doing all kinds of things, they're adapted to their environment, they're constantly taking action, changing their environment, taking things in, putting things back out. Um and really the large animals, as we saw from the the sort of the plots at the start, not exactly an afterthought, but definitely sort of a lot further down the chain of things that happen. Um there is so it turns out that biologists have a sense of humour, and I had never seen this until I looked at this plot, but right in here, where you won't be able to see, there's a bit in here and it says Loki and Thor. And I thought that must be a spelling mistake, so I looked it up. And it turns out that there is, these are very ancient organisms, single cells. It's thought that they go way back, that they're very important in early life, and so they're unofficially called the Asgard Archaea, which is just a lovely idea that you know if we go right back to the root of life, what we actually find are Norse gods. Anyway, so um the point is that we are living in a microbial world, not just by mass, as we saw at the start, but in terms of diversity, we are relatively niche compared with the life that's on Earth. Um, so I want to give you an example of how, in some senses, everything that came after the microbes is sort of dependent on them. And there's lots of examples of this. This kind of stuff is happening all over the place. But this is my current favorite. Um, so I don't know how much you think about vitamins, how many of you take vitamin supplements, for example. Uh, but here are the molecular structures of some common vitamins. Uh, A, B, C, D, they all, you know, they've got familiar names. The important point about this, so vitamins are essential, we need them to live. And these are all quite small molecules. The structures, the details of the structures don't really matter. What matters is you can sort of put all of these on a in a little box, and it kind of looks like a manageable molecule. And there's one vitamin which is an exception to this pattern. There's a monster. There's a monster hiding under the bed, and it's vitamin B12, which is this colossal thing. It's got cobalt at its core. It's really complicated. The bits where there's an R are another whole little complicated thing there. Um, and vitamin B12 is essential for us. We need it for DNA replication, it's important for metabolizing things like amino acids and fatty acids. It's an absolutely crucial bit of biochemical machinery that we need in order for our bodies to function. So let's have a look at where vitamin B12 exists in the natural world. So we're going to go back to this uh plot of all life on earth here. So, animals, every single animal needs vitamin B12, and none of us can make it. So it's not coming from us. Uh the plants don't have it and they don't need it. They've got other biochemical ways of uh fulfilling that function, so they don't have any, and the fungi don't have it and don't need it. So just not there. And then there's these two groups here, um, the bacteria and the archaea, and they might be able to, they might need it, and some of them, it seems, might need it for fermentation. That seems to be what it's useful for. Uh, and if they need it, they can make it. So basically, the only source of this thing in nature is fundamentally the bacteria. Uh, so let's have a think about how in practice we all get vitamin B12 or how different animals get it. So let's start with a cow, uh, herbivore, right? So it eats plants, not getting any vitamin B12 from plants. But what it does have is a gut which is very, it's quite long and complicated, but inside its gut, up near the top, is there are bacteria, and those bacteria are fermenting. So as long as the cow gets enough cobalt in its mouth to add into the bioreactor with all the uh with all the every all the bacteria, the bacteria will make B12, and it's happening far enough up the digestive tract that the cow can absorb it. So that's how cows get their vitamin B12. But then it gets a bit more interesting. I don't know how many of you had pet rabbits or observed your pet rabbits. Pet rabbits and other rabbits have a completely different mechanism for dealing with this. So if you feed a rabbit, uh you feed it something that's quite fibrous, and that goes down into the rabbit, and then the stomach of the rabbit basically sorts it by size, and it leaves the big bits to carry on down the digestive tract, takes the small bits and squirrels them away in a separate little compartment, which is a bioreactor. It's got bacteria in it, they can break down the fibre, and critically, they can make vitamin B12. But then the rabbit has vitamin D B12 inside this little container inside itself, and that's no use to the rabbit. So it can't get at it, can't get at anything from there. It's got to have another go. So you may have seen a rabbit do this. They're quite uh they're quite subtle about it, tends to happen at night. But this little ball of vitamin B12 and digested fiber gets covered in mucus, it goes back into the rabbit's digestive tract down the bottom end, it goes all the way down, comes out the end, the rabbit eats that ball straight out of its own anus, so it goes back around again, and then it can go down inside the rabbit, and that's how rabbits get vitamin B12. It's incredibly elaborate, right? But they can only do it because there are bacteria, they need to work with bacteria in order to emphasize in order to get access to this thing. Now, I'm not gonna ask about your it's not normal feces by the way, so they're not eating their normal poo. They're very they know only to eat this very specific little ball of mucus covered stuff when it comes out. Kind of making their own marmite in some ways. Anyway, um so how about how about how about humans? Um we we I'm not gonna ask about your feces eating habits or otherwise, but fortunately, humans also generally rely on bacteria. So um, if you have a plant-based diet, you're not getting it from plants and you're not getting it from fungi. So, where do you get it from? You have to get it from things that are fermenting. Uh, and so there are a range of bacteria that do ferment. If you have kimchi, for example, there's fermentation that goes on that's got vitamin B12 in it. It's actually added to marmite, it's not in that fermentation process the first time around. Other B vitamins are, but but uh vitamin B12 isn't. Um, but when it's produced industrially, it's done by fermentation. And what it's not the most common bacteria used, but one of the bacteria that is used to make vitamin B12 is the one that makes the holes in Emantal cheese, which is rather lovely. So the point is that the entire animal kingdom depends on something that is basically an accidental byproduct of something that a bacterium is trying to do. They're not doing it for us, they're just getting on with life. But this byproduct then enables a whole load of other biochemistry, which we absolutely rely on, and this is far from the only example of this. Um so so we live in we live in a world where there's no such thing really as a single organism, unless possibly you're a microbe and you can manufacture everything you need, and even then you're dependent on other things going on around you. So that's that's the kind of summary of all life on Earth, right? Mostly microbes. Microbes are these little factories which are doing all kinds of useful things. Um, and we humans are really occupying only a corner of the total amount of life, but an increasingly significant one. So then let's get to what life is all doing, because it's really busy, right? Life is a process. What it's doing is taking in atoms and energy from its surroundings, it's kind of processing in order to keep it going, and then it's giving them back out into the environment one way or another. Everything sort of passes through. So, and the point is that all of that, just like the vitamin B12, it's got an impact on its environment. So no living creature lives in a vacuum. Uh, it has to, it's interacting with its environment just by existing, it's changing everything around it. So I've come up with, I picked out some of the major things that life does, these functions. And of course, you can't necessarily split them all up, they're not all entirely separate. But life moves things around, it takes things in, it gives things back out, it transforms molecules or atoms from one type into another, um, it changes structures and it sorts things out or filters things. And these are just the big ones, but they're quite big categories. So, what I wanted to do next is just go through a couple of examples of how this works, like how interwoven all of these processes are, because basically all of this is what creates the world we live in. So things in. This is a very common tropical fish, it's called a parrot fish. It's one of my bees in my bonnet in life that um almost all, like so many fish in the ocean are named after animals, goat fish, sheep's head, rass, parrot fish, right? And sometimes frogfish. Sometimes there's a like a kernel of a truth somewhere. Sometimes someone's just come up with a name because they felt like it. But in this case, this fish does actually have a beak. Um, and it's got quite a dramatic beak. It's got teeth that are fused together, so it's got 15 or so rows of teeth, thousands of teeth are in there, and they're all kind of fused together, cemented together, covered by a layer of bone, and they are phenomenally hard. And the reason they're phenomenally hard is the way a parrot fish um lives is it rasps away at coral, and it's not really eating the coral. What it's after is the algae that grows on the coral, not the uh symbionts of the coral, but algae that's just sort of growing on the coral surface. And so it rasps away really hard material, and then its teeth get even weirder because it's not just got one set at the front, the beak that's doing the rasping, it's got a second set further back. Because then it's rasped off all these bits of hard stuff with algae and it's got to grind them all up. So it grinds them all up. Um, and the I mean, there's a sort of sidebar here about how the how clever this physical process is. This is um not true colour, but somebody scanned a uh does a sort of CT scan of a parrotfish beak, and you can see there's these rows of teeth all fused together to make this incredibly hard material. And then the plot on the top right, or top left, sorry, is just shows you some where it where that material sits in all the sort of biological materials. So we've got hardness along the bottom and effectively stiffness up the side. And parrotfish enameled teeth are the stiffest known material in nature. They're almost as hard as shark teeth, but not quite. So this is quite a you know fantastically impressive biological material. But the reason I'm talking about it is that parrotfish rasp away, bits of coral go into the parrotfish's mouth, get ground up, they extract the algae and all the nutrition, and then all the bits left over have to go somewhere. And it has been some lucky biologist's job to collect what comes out of the other end of the parrotfish and measure it. And if you do that, these are these are just two of the plots. I think there are about eight in the paper I took this from. So we've got sizes here, grain size in microns. So that's this is a millimeter uh there, and then you can see smaller classes there. Um, the number up the side is just frequency, these are slightly different species of parrot fish. But anyway, the point is it's all really small. So all of that comes out of the back end of a parrotfish, and then where does it go? Well, if you have ever been or wanted to go onto onto somewhere uh where they have white beaches, that's stuff that you might be paying huge amounts of money to walk along on a tropical beach is almost all parrotfish poop. It's all been through the middle of a parrotfish, right? Um, which you know it's just got to make spending that money feel even. You've got to feel even better about yourself, haven't you? But the point is that this is happening on a large enough scale that they are shaping the environment. Parrotfish are not doing it because they want to be engineers, they're doing it because there's a process they have to go through to live, and the byproduct is that it shapes the world around them. Um so, as I said, there's sort of overlap. So that was sort of things in. Let's have a look at another example of things out and that having an influence on the world. Um, this is the coast just off, this was taken in Hawaii, um, and but it looks like the ocean, you know, there's sort of rocks and waves, and the water's blue, and looks like the ocean. But if I was to ask you what this smelt like, you would guess almost immediately, right? Because we know what the smell of the sea is. It's this kind of uh very sort of tangy smell that's very distinctive. And that smell comes from a group of molecules that all come from the same precursor, the same thing to start with. And it goes by the terribly sexy name of DMS, which stands for dimethyl sulfide. You don't have to remember that, it doesn't matter. The point is that this is what this is where the smell of the sea comes from, fundamentally from one type of molecule. So let's follow what happens to this molecule, where it comes from and where it goes to. It's produced by a huge variety of phytoplankton, which are the tiny single-celled microbes, organisms that live in the top of the sea, they're taking sunlight, building it up into sugars, and then usually something else comes along and eats them. So this is just one example, it doesn't have to be this. So it seems that they produce DMS to help them when they're stressed. And so if something comes along that stresses them, maybe there's lots of UV light or something's trying to eat them, any of these things, they produce this substance, dimethyl sulfide. And then they don't really care about what happens to it next, but some of it leaks into the water. And actually they produce this precursor that's called DMSP, uh DM DMSP, that turns into the DMS, the dimethyl sulfide. And then most of that stays in the ocean, it just gets dissolved or consumed or just hangs around in the water and goes away. But a small proportion of it will get given off into the atmosphere. Um, and what happens there is a series of chemical reactions that can turn it into tiny, tiny liquid droplets that have got that based on sulfur. They've got chemistry based on sulfur. So the tiny, tiny droplets are called aerosols. So these are sulfur aerosols, and then the reason that they matter is that high up in the sky we just take for granted that you have clouds. But you don't necessarily just have clouds, you you only really have clouds when there was some tiny little thing in the atmosphere that the water could condense onto. And so the tiny, tiny little things are called cloud condensation nuclei, and then water will sort of collect on them, and that's what forms a cloud droplet. So every tiny droplet in an enormous cloud had some tiny, tiny little thing right at the centre of it. And it turns out that over the ocean, an enormous proportion, it's hard to measure exactly, but it seems that the dominant cloud condensation nuclei is these sulfur aerosols, these sulfate aerosols that came from marine phytoplankton having a bad day. And you can actually measure the effect of this on the ocean because those clouds, well, you can measure the effect on the climate because clouds are white, they're reflective. And so when the sun comes in, it can reflect off the cloud and just go straight back into space without ever getting to the ground. So if you have more clouds generally, they will shade the ground so the it'll be cooler down below because the energy's just been sent straight back into space. We can measure that cooling effect. Um and there's the cloud. Right. So this is uh a line taken from papers written by one of my colleagues that um the resulting climate cooling effect of all the DMS is around two-ish watts per square meter. Don't worry about the numbers, but the point is that that cooling is about similar in magnitude to the warming caused by humans emitting carbon dioxide. Now, the point of this is not to equate one to the other and say that, well, you know, the the bacteria have, you know, the algae have saved us all from further global warming. The point is to say that it's significant. We know that the amount of carbon dioxide we're putting into the atmosphere has caused a significant amount of warming. Well, the bacteria doing things by accident have put something else into the atmosphere, which is part of our world now, which causes a significant amount of cooling. So again, this microbial accident has led to an really important thing: how much energy gets into Earth, which is a critical feature in the running of the Earth engine. Um, so again, tiny, tiny animals, tiny organisms with huge consequences. So let's carry on to uh a couple a couple of other examples here. So building structures is a fun one, right? Because animals are always, you know, they're very active, they're doing things, and there's a whole class of things that they could be doing. So uh they might be digging burrows. I think the numbers on here are numbers of classes of animals that do that, it's not species. Um they might mix things up, they might dig, change the structure of things, they might forage, they might make nests, they're doing all these things, they're moving things around in the world. And so the question then is okay, animals are doing a lot of work. But as they would say on more or less on Radio 4, is it a big number? Is it is a lot of work a really significant amount of work? How do we count this? So biologists have had a go at counting this relatively recently, and the way they've done it is by measuring literally the amount of work, the amount of energy which has been expended building things or moving things, and they've compared it to some processes, sort of physical processes like landslides and things, that so we can make a comparison. So the plot I'm about to show you looks a bit complicated, but we're going to look at the bottom bit of it first, and what that shows is the amount of energy used. So let's here's the big plot from the paper. And so here we've got energy used for the work along the bottom on a log scale. So these on the on the right hand side, that's a really, really, really big number. Let's look first at everything below the red line. And we can see that we've got a flood, extraordinary flood, um, a monsoon and processes to do with mountain slopes eroding away. And they're all relatively small amounts of energy on this scale. And like imagine like a monsoon has a colossal amount of energy, you know, to move things around, but it's relatively small on this scale. So now up the side we can see different animals and the amount of work that they are doing per year, I think this is. And you can see that all wild land animals up there have a huge, huge amount of energy is being expended there. And then we go down, so you know, rodents are busy burrowing. Elephants are really important because they're kind of crushing vegetation that creates space for new vegetation to grow. So animal uh elephants are actually really big ecosystem engineers, go all the way down the line here. But then right at the bottom, just above the red line, livestock, right? Remember that plot at the start that showed that livestock had a larger biomass even than humans. And we can see that the amount of what's called geomorphic work, the amount of work that they are sort of churning things up, moving things around, is far larger than anything else. So the animals that we are putting into, all of these animals are doing a significant amount of work shaping their environment, but the animals that we have put into the environment have an even bigger effect than that. Um, but just as an example of a small creature having a large effect, um may have seen ant people talk about ant hills. I'm not sure how many people know when they're looking at an ant hill because they're often quite well disguised. So ants live in colonies, and those colonies uh depending the the amount of this they do depends on the species, but they will dig down and excavate lots of tunnels and create, some of them go quite deep, creating nests that are tunnels everywhere. And of course, if you move all of that earth out of the tunnels, it has to go somewhere, so it piles up on top. And some species of ants then use that mound to create to make the structure even bigger, to add tunnels and entrances and exits, so they create this structure. Um, so these are ant hills that have been grown over with grass on the bottom. That is a very large ant hill at the top. And just as an interesting comparison, here are the uh the Great Pyramid and the ones next to it. And if you take the ratio of the size of one human being to the scale of the Great Pyramid of Giza, we get a ratio of about one to 69 million. So, you know, a lot of slave labor went into building that, huge effort. But when you look at the size of an ant compared with the size of the largest ant hills that get made, it's one to six billion. It's a gigantic number. So an ant is a very tiny thing, but they can make structures big enough that they are significant in the environment. And the reason they're significant is not just that they change the shape of things, it's that they change how the environment responds to floods. And this can happen in two ways. Um either when it floods, or you get a lot of rain, the water just goes, it just fills up the ant's nest, right? So the ants have conveniently created a kind of drainage system and the water can just go down the drain. So if you only get a bit of rain, the ant the ant nest kind of fills up with water, the ants mostly cope, sort of, and then um that water isn't running around the surface flooding. But the other thing that can happen is that the ants have excavated a load of soil, so they've made it loose, so it's more likely to be carried off. So if you get a really big flood, the nest fills up with water, you've got still got extra water, and then there's all this loose earth, and then it's more likely to get carried away. So the ant the structure that the ant is making can either make floods worse or better depending on the environment. But the point is that either way it matters. Okay, last example of these is just an example of animals moving things around, and this one is an animal in this case. And to set this up, I want I'm gonna show you a map of a particular nutrient in the ocean. So there are some major nutrients that are essential for life uh nitrogen, phosphorus, potassium, and so on. And so I'm gonna show you a map of nitrate in the ocean. So it's distributed across the ocean, but it's not distributed evenly. And this is an essential nutrient, so so organisms need this to live. So here's the map, and we can see that there's a lot of nitrates in the southern ocean, um, but then large parts of the open ocean are really dark blue. There's almost no nitrogen there, and nitrogen is essential for life. And I want to look at one particular area, which is the island of Hawaii, there with the red circle around it, and you can see that Hawaii is sitting right in a nitrate desert, right? So it's not getting nitrate from the water around it. But we know that the area around Hawaii is that the ocean does have quite a bit of life in it, so it must be getting nitrate from somewhere. So the question is, where is it coming from? And the answer, a large part of the answer, is that animals are bringing it there. And the animals in this case are humpback whales. So humpback whales have this life cycle where they feed in very cold, nutrient-rich waters to the north and to the south in Antarctica. So that blooped sort of turquoise band along the top, cold water, that's where humpback whales are feeding. They're taking in food, they're getting fat, uh, and they are uh taking in lots of nitrate, nitrogen. And then when they're ready to breed, they go on this colossal migration, thousands of miles. And quite a lot of whales, humpback whales that um are feeding up there will come to a tropical island in order to breed. It gives them protection, it uh allows them to hide from predators, it makes it harder for things to attack them, it's nice and warm, it's a good place for calves to be born. So they the the animals, the whales stop feeding, they travel to Hawaii, um, and then sometime later they go back to their nutrient-rich feeding grounds with their new calf. So, this in this process, whales are moving things around, and this has been given the lovely phrase, the great whale conveyor belt. So, how much does it matter? And what is it anyway? So, the reason that the whales are conveying things is that they eat in the cold places, and then when they start to travel, they stop eating, they're living off their fat reserves, but they don't stop metabolizing. So they continue to produce urea and feces, and they occasionally die, and that obviously delivers a load of nutrients to the seabed. So we can look in Hawaii at the, and this has been added up, proper scientific study. We can look at the amount of nitrogen that is around the Hawaiian Islands because the humpback whales brought it, and we can compare it to the little bit of upwelling, the physical process that brings nitrogen from underneath. And the comparison is really, really stark. So you can see the physical processes are at the bottom here. So a decent chunk of nitrogen is coming from water upwelling from underneath. But the whales are delivering a colossal amount of nitrogen, far, far more. And bear in mind that this is uh after, you know, so humpback whales have recovered a reasonable amount, but they're still not at their pre-whaling levels. And so the nitrogen they would bring would have been even higher in the past. So even a whale, even a creature like a whale that travels to somewhere, it doesn't eat anything, it's still carrying things across the world. This is the uh, I think it's the longest known migration of a large mammal. And it's not just that the animal is moving itself, it's moving stuff, taking it to a new place and depositing it there, and that is changing the environment and making life possible where it arrives. So the point about all of this is that life is woven through the dynamics of Earth. It's not just that animals are sitting on top, they're an active part of what's going on around them, they're shaping the world. Um, and uh, so when we look at this image of Earth, what we should see is not just the stage on which the theatre. Is that the step that on which the play is played out? It's that life is the theatre, right? It's all mixed into one. It's not a case of all the world's a stage and all the animals are merely players. It's a case of everything is both, right? Everything is all together. It's both the stage and the player. Everything is woven in together. So now we get to the depressing bit. So you're ready. What's changing in all of this? Because things are changing. And the I want to use an ocean example here because it's kind of it's been relatively well measured. It's kind of easier to see. So I showed you before that life in the ocean, life overall tends to be either very small or very large. That's not true for life in the ocean. Life in the ocean is very different. So what this is this is a plot of all the life in the ocean, and we've got size going along the bottom from the biggest blue whales on the right down to the tiniest, tiniest little microbes on the left. And up the side is the amount of biomass. And the important thing here, the really striking thing about this plot that surprised everybody when this was published, is that it's almost the same. Whatever size category you're in, it's got the same amount of life in it. So if you double the size you're looking at and add up all the life, it adds up to the same number. And that is true all the way up until you get to the bigger things. And the bigger things aren't there because humans have fished them out and eaten them. It turns out that the best way to survive is to be too small to be seen. Unfortunately for everybody, most life in the ocean, about two-thirds of it, is too small for humans to see. So we haven't got to it yet. We haven't gone fishing for it. But the authors of this paper did something else. They looked back at what the biomass would have been like before 1850, which is considered, you know, there's an area, a period of dramatic expansion in human civilization. And the pink bits are the animals that would have been there in 1850 but are not there now. And you can see that it's the bigger ones that are missing. We've just taken the biggest size fractions out of the ocean. And then they plotted this in a slightly different way. So then this plot here is got mass body mass along the bottom again, but there's a percentage loss up the side, and you can see that the biggest losses are in the animals of the sizes that we can see, right? So up to sort of 90% of animals in those biggest size classes have been lost because of fishing. But that's the pink kind of hatched bit with the lines. Then there's this sort of softer pink block colour, and that is the projected losses due to climate change. So that's not humans going out with a fishing rod, that's the climate changing and less life growing as a result. And you can see that here being small is no defense. So it's still they're relatively low numbers, it's down in the 10 to 20%, but still that's a lot of life that isn't there because of climate change, because we've changed the environment. Um, so how do we measure all this, right? We're good at measuring things, maybe, even if we're not very good at looking after things. So, how how do we think about all this? You've probably heard of the um IUCN Red List. This is when you have those phrases that people say, oh, it's an endangered species, it's of least concern, uh, it's vulnerable. There are these categories, right? You've probably heard those categories. And so the IUCN is an organization that goes around assessing animals, it looks at their habitat and the numbers and it says, well, are they are they critically endangered? Are they threatened or are they of least concern? And so they have measured this for thousands and thousands of species. And this is the plot of what they've found, right? So the green things are all the ones of least concern. Uh, there's a big chunk of animals where we just don't have any data, and then varying levels of concern around here. Now, this looks quite serious, right? Just under half of animals are probably not doing very well, or we don't know. Um so that sounds bad. It's about to get worse. Um, a few years ago, a couple of in the past couple of years, you might have seen these headlines coming along. And I'm going to use this as an example of why it is that that pie chart doesn't show the whole picture. So you may remember, so tuna, bluefin tuna have come back to Cornwall. It's genuinely exciting, right? This really rare species has come back, it's living off the off our own coasts. And there were headlines all over the place about it. Um, and it is genuinely coming back. If we look at the data, uh, this is from uh one of the papers studying this. You can see pictures of the tuna that were taken off Cornwall here. And then this map on the right hand side, the dots are places where bluefin tuna have been seen. And so you can see there genuinely are bluefin tuna off the coast of Cornwall. It's brilliant. Um, but that wasn't the only thing. It really bugged me at this time that if I if I Googled bluefin tuna, what I saw was things like this. A load of humans had gone, yay, fishing! Now we can fish all the bluefin tuna, let's start a fishery. Seriously, the top 10 sort of entries on Google were all about yay, we can fish, which really annoyed me because I was like, can we not just leave balone? I mean, wouldn't it be nice to look at them? Anyway, but that's not that wasn't that was my first reaction, and then my second reaction was hang on, I thought bluefin tuna were endangered. Why is anybody allowed to fish them, right? That doesn't sound right. So I went back and looked, I looked at the IUCN reports on bluefin tuna, and these are screenshots of the IUCN reports on the Atlantic Bluefin tuna. So um uh that's its name at the top, uh, and we can see in 2015 bluefin tuna were endangered. So I wasn't wrong, they were definitely endangered, but then there's been a more recent assessment since then in 2021, and now they're of least concern. And I thought that's odd. How does a species go from being endangered to being of least concern in five years? And then I did something that I hadn't done before, which was I went back and looked at the definition of what what it is that makes how do they decide which of these categories a species is in? And I noticed something in the wording that I hadn't seen before, and this is how that wording came out in the paper on bluefin tuna. It said, as there's been little estimated change in the overall global biomass, the species is listed as least concern. So it's not that the species is doing well, it's that it hasn't got any worse. And this is not the IUCN's fault. They're quite clear in their guidelines about what it is they're doing and what it is they're not. What they're concerned about is is this species going to disappear? Do we need to worry about this species disappearing in the next 10 years? And if the numbers are going down, then we probably do. But of least concern does not mean that the species is healthy, that the population is healthy. It just means it's not getting worse. Um so they they clearly know about this. They have have had, they're aware of this, and they have actually got, they've just sort of a while ago, they announced a different sort of list, except they're not calling it a list. They're calling it the green status, and it's not really developed yet, it seems to be early days for this. But the point of this is that instead of starting from it's not bad, this is going to be a measure of is it actually good? And they haven't published, as far as I can find, any lists of animals in this yet, but they're thinking along these lines, and they're also doing this for whole ecosystems, not just for individual species. So the point here is that on that pie chart where almost half of everything probably not in a good state, even the bit that's green might not be in a good state. It's just not getting worse. Um, and then there's a subtlety in this, which is uh so you remember at the start we had this plot of all the biomass, and uh we could see that most of the biomass of animals is arthropods, insects, right? Uh and that's what this plot here on the left shows. It's basically the same information, just passed slightly differently. The largest number of species we know about, the most species, that they come in the category of insects, and then we know about fewer species and everything else. And that's just because insects are incredibly diverse. There's loads of them. The smaller things are, the more diverse they are. That seems to be the rule. So then let's have a look at which species the IUCN is using to put into that pie chart. And you'll see that lots of mammals and birds and amphibians are in there, which is great. Very, very, very few insects. And of course, insects are harder to study, partly because there's so many of them, partly because they're very small, hard to find. Um, but it seems that they're hardly assessing insects at all, and yet insects are the largest proportion of described species. And so, I mean, the message really here is that pie chart where it looks like everything might be okay, doesn't actually really show the insects because they haven't measured them. So we don't know, but the estimates for insects, depending on which estimates you believe, maybe between 10 and 40% of them are endangered or imminently at risk of becoming so. So my point is not that the IUCN is doing bad things, it isn't, it's doing a very important job. But my point is it's very easy to be complacent when we see that there are species of these concern, because we're actually doing quite a lot of damage to our uh natural, uh, the natural environment. Um, and they say quite clearly here uh in this is a different paper, but you know, denying this crisis, accepting it and doing nothing about it, or embracing it and manipulating it for the fickle benefit of people, defined no doubt by politicians and business interests, is an abrogation of moral responsibility. So scientists are saying, look, we cannot ignore this, right? We can't just sort of pretend it's not happening or use it to score political points. So then we get to the animal that I haven't mentioned so far, which is us. Um, because we are also, we do all the other things animals do, right? We take things in, we give things out, we struck, we change structures, we move things around, we sort out the world. And these are also having an effect on the environment. We're just like every other animal, we're just doing it differently and on a much, much, much larger scale. And so, just as one very quick example of that, um, I want to pick another nutrient, which is phosphorus, and it's just the big picture here, right? So, here is a plot of how phosphate moved around the world before 1850. And it doesn't really matter, the point is we've got ocean, we've got land and soil, and there's blue arrows moving around. Fine, this is what the phosphate cycle looked like. But then humans found that phosphate was useful as a fertilizer. And if you look at this now, it's got all these extra arrows on it that were not there before. So it's not just that we're moving things on a different scale, we're moving the same things, but we're moving them from and to places they never went from and to before. And actually, global uh stocks of phosphate are, you know, finite because it takes a long time to form. We're in danger at some point in the future of running out of phosphate because we're just taking it out of the landscape, we're moving it around, and then it's getting put into places where we can't kind of get it back into our systems. So humans are having an enormous impact on this world of kind of atoms and energy flowing around. Um, and it made me think of this. So in 1957, 1956, there was a very famous publish uh paper published in oceanography, and this guy, Roger Ravell, uh, was the first author. And this was the paper where he first sort of set out clearly, clocked, that all the extra carbon dioxide in the atmosphere was going to have an effect. And he didn't know, you know, he didn't know the scale of it, he just sort of saw it as, you know, this is was sort of interesting. But he wrote this very famous line in this paper. He said, human beings are now carrying out a large-scale geophysical experiment of a type that could not have happened in the past nor be reproduced in the future. And this that's that's the line that's held up. He didn't really see it as a bad thing back then. He just said, look, this is going to have consequences. We don't know whether they're good or they're bad, but we humans, this animal, has now our actions are big enough to have consequences, big enough to impact the climate. So that's about carbon dioxide. But I think that the thing that is very clear, having seen the evidence that I've just showed you, is that we are also now carrying out a very large-scale biological experiment. And um, it has actually been carried out before. There have been five previous mass extinctions. We can see in the fossil record some of the deep some of what happened, not all of it. Um, but the point is that we can't treat life as either a luxury or as an irrelevance because the life that lives in this planet, all of us, it's all doing things, it's all building our world. And it needs to be part of the system, it's part of our life support system. So I'm all for, you know, keep saving the pandas because they're cute. That's fine. But I'm also for saving the pandas because they are an important part of an ecosystem, and we are in that ecosystem. And so life is not just there as a beautiful thing, it's a necessary thing. And by cutting those links and making them shorter, making them thinner, making them weaker, fundamentally we're hurting the foot the real engine of the planet, and we're also hurting ourselves. So, on that lovely, cheerful conclusion, uh, here's the summary. Basically, so life on Earth is varied and diverse, but we live in a microbial world. It's the small stuff that is really running things. Um, all of life is doing things. I've given you the tiniest flavour of how that works. Um, and we are carrying out this huge experiment, uh, but we have a choice, right? We do have choices, we're not passive in this. The advantage we have that most other animals don't have is that we can plan, we can gather evidence, and we can make decisions. And so I think we need a big change in our view of what life is, because I think politicians now regard life as a nice, cute thing that people like. But what they don't necessarily see all the worms and the insects and the tiny beetles and bugs and microbes are microbes as is the thing that is keeping us alive, and I think we all should. Thank you.