How Has Biodiversity Changed Over Millions of Years?

00:00:00: Fritz: Today, we have a lot fewer mammals than we should have because speaking in geological terms, these megafaunal extinctions were very recent. They only happened 10 to 50,000 years ago, which is the blink of an eye if you measure diversity in 1 million-year intervals. So maybe we're still in kind of the recovery from this extinction, maybe there is speciation ongoing, if we let it run for long enough, there would be large mammals again, they would just be more adapted to warmer environments, probably.

00:00:32: Hahn: Welcome to #InsideBiodiversity. This podcast is hosted by iDiv, the German Centre for Integrative Biodiversity Research. My name is Volker Hahn. I'm head of the communications unit at iDiv, and my guest today is Susanne Fritz. Susanne is head of the Biodiversity in the Anthropocene research group at iDiv, and she's also a professor at the Friedrich Schiller University Jena. A main topic of her research is biodiversity change over very long timescales, so thousands of years and millions of years. I am very excited to have her here today. Welcome, Susanne.

00:01:11: Fritz: Thanks for inviting me. It's a pleasure to be here.

00:01:14: Hahn: Let's start with your motivation to do research. And today we'll talk a lot about mammals and about birds on long timescales. Why did you decide to research these animals?

00:01:29: Fritz: Um, yeah. I don't really have a very straight, um, answer for this. I think I was always interested in nature. I like being outside and I like seeing what is there around me. And of course, birds are very noticeable in general mammals also if you're in the right areas. Um, and then when I studied, I originally thought I would do genetics because I was interested in evolutionary biology, but then I realised that I was more interested in understanding biodiversity Velocity in terms of the organisms and the species. So why do we see some species where they are? Some others we don't see in certain places. And then if you're interested in big questions like this, there's just a lot more data available for birds and mammals because they're easier to notice, easier to record, more people work on them. I actually started out studying amphibians because I like frogs.

00:02:22: Hahn: Okay, so you basically like most animals. Exactly, I guess, and they're practical reasons and and emotional reasons for why you did that. Okay. In previous podcast episodes we've talked about biodiversity change, usually on the scales of of decades like 20, 40, 50 years or maybe 100 years. What are the timescales you are looking at in your research?

00:02:52: Fritz: Um, we partly look at these shorter timescales. I'm going to call them also because I'm also interested in biodiversity loss that is ongoing through human activity and in the effects of ongoing climate change. So then you end up on shorter timescales. But what I also focus on a lot is more the evolutionary side. So how has biodiversity evolved to be what it is today? Because of course, everything on earth has a million years of history behind it. And I just find it fascinating. I mean, it goes back to going to a museum and seeing dinosaurs right in the end. It's what kids get excited about at an early age, because it's just so fascinating that the world we live in was so different in terms of nature over most of its history. And if you study mammals and birds, the relevant timescales are usually mostly the last 66 million years. So since the non bird dinosaurs went extinct because birds are of course actually dinosaurs. Mhm. Um and yeah. So that's.

00:03:51: Hahn: So that was the, the last major mass extinction. The fifth mass extinction Yes, 66 million years ago, when the dinosaurs, except the birds went extinct.

00:04:02: Fritz: Exactly. And the crocodiles.

00:04:04: Hahn: And the crocodiles.

00:04:04: Fritz: They kind of could be argued to be closely related to dinosaurs. Um, yeah. So, uh, it's, uh. The five mass extinction is a bit, um, argued about in palaeontology. You could also say there have been 113 mass extinctions. It depends which definition you use. But certainly the one, 65, 66 million years ago was one of the largest ones. Yeah.

00:04:28: Hahn: So these are the timescales we're talking about. And for our audience to put this into perspective, um, I think humans have in the broadest sense, humans have been around for 2 million years in the genus Homo. And and modern Homo sapiens are around for like 300,000 years. Yes.

00:04:51: Fritz: So maximum.

00:04:51: Hahn: I think much shorter timescales. And as I said in previous episodes of #InsideBiodiversity, we talked about 50 or 100 years, so we have to keep that in mind. And that's a bit difficult to also have these different events.

00:05:08: Fritz: But I always argue that it's important to look at these longer timescales because it makes us understand how the system works without humans. Right. So if you're interested in human influence, the baseline that you should look at is, of course, before humans were around to change biodiversity patterns and to at least now change even the climate.

00:05:28: Hahn: Okay, let's talk about the longer timescales. And you've looked at biodiversity of mammals over the past I think like 15, 20 million years. Can you tell us about how has mammal diversity changed over that time period?

00:05:50: Fritz: Yeah, so we looked in these studies, we mostly looked at Europe and North America. Because if you work with the fossil record, it's of course very different to working with present day data. Today we can just go outside and observe birds in Ecuador or observe them here with the same method. And then we know what biodiversity is in Ecuador in here. But in the fossil record you're restricted to where you find specific age rocks. Right. So if we're interested in the last 15 million years, we only have certain places where these rocks are where we could even find the fossils. And that means that we had to select the regions a bit carefully. So we decided for Europe and North America, because there are good databases around, um, that we had to still check and bring together. But it worked. Um, and the, the cool thing to see is how much biodiversity really changes. So it's a bit tricky to estimate it because you know that the fossil record is never complete, but there are statistical methods to estimate it. And depending how we estimate it, we get, um, for example, in Europe, a diversity that was at times 3 to 8 times higher than today. Um, and of course, the big question is then why. Right. And in the papers that I've done, we've mostly looked at.

00:07:06: Hahn: That's like 20 million years ago, it was. Yes. Would you say five times higher?

00:07:11: Fritz: I think it was around 11 million years at its highest, maybe 13 million years. And, um, it's been mostly declining since then with some ups and downs. And these ups and downs are of course, significant. And you have to bear in mind that the timescales, if we look through such a deep time record, we need to divide it into passes in which we count the the biodiversity in which we count the number of mammals, in this case number of mammal genera. And we used um, 1 to 2 million year time bins. So what you end up is the number of mammal genera in a 1 million year time bin, for example, which is of course very hard to compare with numbers we have for today. because today is really quite recent in geological terms. The period we're in is the Holocene, and that's only 12,700 years.

00:08:04: Hahn: So it's a much broader way of looking at biodiversity, both in terms of the diversity and in terms of time.

00:08:13: Fritz: Exactly.

00:08:15: Hahn: So what? So you said that over the last 10 million years, biodiversity has declined until today. Uh, what are the main or what were the main reasons for that? And let's exclude like human influence over the the past few thousand years.

00:08:35: Fritz: Yeah. Um, so there have been some ups and downs and it's regionally different. So we know that there's not one global driver that explains everything everywhere, of course. Um, but it, uh, in the one paper that we've done, we've compared, the number of mammals that were around. Number of mammalian genera with the productivity of plants. So basically the biomass that plants produce. Um, which of course is what mammals in the independent. Because many mammals are herbivores, they eat plants directly. So they need leaves or grass. And then the carnivorous mammals feed on the herbivorous mammals. So the meat eaters feed on the plant eaters. And then that means that the energy you get into a terrestrial ecosystem, into an ecosystem on land, usually comes from the plants that do the photosynthesis. And it makes total sense, right? So what we found was that, um, the higher the plant productivity, the more mammalian genera we had. And this was through this, let's say it was 15 million years, I think, um, record, which was surprising me because it's usually not that simple with biological data, but it was a very strong signal.

00:09:49: Hahn: So how could you assess plant productivity? How did you know how high that was during certain time periods?

00:09:58: Fritz: Um, you have plant fossils, plant microfossils. And there is there are different methods to then reconstruct, um, from these plant microfossils, roughly what the temperature and precipitation was. And then you calculate what the productivity was based on that. So it's a very roundabout way because we don't of course, we can't just go and mow a field like we would do today and see what the biomass is.

00:10:25: Hahn: So where's the link from climate to productivity to mammal diversity? Is that the causation?

00:10:35: Fritz: Yeah. So we're not sure because we've done correlations right. So we know that productivity is correlated with the number of mammals. Um the mechanism behind it could be just that the mammals need to feed more. Right. So if you want more mammalian species. You also need more energy in the system, more plant biomass. There could be the link through the climate which people have proposed for a number of years, a direct influence of climate on the mammals because mammals evolved in warmer time periods, right? So they evolved more in tropical climates, subtropical climates. And even today we find way higher diversity in the tropics for mammals. Right. So there's just more species that can live in these tropical environments. There will be a more direct link of the climate. But of course, the climate also influences the plants. So the warmer and moister the climate, the higher the plant productivity, partly because you get different ecosystems. So if we're talking 15 million years ago in Europe, there was a warm temperate to subtropical forests. So it was much warmer than today and probably good water availability in North America. Things dried up earlier already, so the continent dried up a bit earlier than the European continent, so plant production was also a bit less there. We can even see that in our database.

00:12:00: Hahn: So you found that there were a lot of fluctuations, but in general over the last 10 million years, Earth cooled. And then we entered a couple of thousand years ago, we entered the Pleistocene.

00:12:16: Fritz: So a couple of million.

00:12:17: Hahn: A couple of million years. Yes, like two, 2.5 million years ago, I think we entered the Pleistocene, the cold era. And then like a few thousand years ago, 50 to 10,000 years ago, there was the late Pleistocene extinction event. Can you tell us what happened then?

00:12:38: Fritz: Yeah, it used to be a big debate, but I think most scientists now believe that it was a mix of things that influenced this. So mostly.

00:12:46: Hahn: Let's not talk about the, the.

00:12:47: Fritz: The interesting thing mostly is what went extinct. Yeah, sure. You're right. Yeah. Um, so we call it the megafaunal extinctions because mostly large animals went extinct. So it's mostly the mammals that we know very well. Um, and the extinctions happened on nearly all continents except Africa. Uh, the mammoth was a late, uh, victim. It actually clung on in Siberia until only a few thousand years ago. Um, the woolly rhino might be something. Sabre toothed cats. Of course, there was a very cool giant sloth in South America that went extinct. There were also some large reptiles and large birds that went extinct. Um, so it was really. That's why it's called megafaunal. It's really the organisms that were large, that predominantly went extinct.

00:13:36: Hahn: Can you also say something about the reasons? Do we know what caused these extinctions?

00:13:43: Fritz: Yeah. It used to be a very large debate whether humans caused them more the climate change, because of course, at the end of the Pleistocene, we also still have these glacial interglacial cycles, ice ages that came and went and, um, especially coming out of the last glacial of the last glacier of the last ice age, if you want.

00:14:05: Hahn: Um, like 10,000 years ago.

00:14:07: Fritz: I think the last glacial maximum was around 20,000 years ago. And then the warming wasn't, of course, continuous. There were some phases where warming was very rapid and people used to associate some extinction events. Of course, also with the global warming, if you think about mammoths, they need this kind of tundra steppe region, the mammoth steppe. It was called, um, that doesn't exist anymore, really, this ecosystem. Um, and of course, that probably got lost in large parts of the globe because the climate changed and they were retreating to the poles to say towards Siberia, um, in the end. But, uh, in many cases, we now have quite good evidence that humans did play a role. So at the same time, we have a large increase in the human population density in many continents. Depends, of course, which continent you look at when they reach North America, South America and so on. Um, but, uh, it seems that it's, uh, the increase in the number of humans. And with that, of course, humans change habitats because they start in the end, we start being sessile. We make agriculture. Right. That's a very strong influence on the world we have around us, shaping entire habitats in a different way. Um, at the start, it's usually thought this direct hunting pressure on some of those large species that are not very fast in reproducing. If you just hunt them to extinction, like we nearly did with the bison in North America in the 20th century. Um, so that that is what people now think, that it's a mix of reasons. It's this mix of habitat loss from climate warming for some species. And then the hunting and habitat alterations that humans do.

00:15:51: Hahn: Now we're in a phase where climate is warming again. We have human influence, humans hunting and exploiting the the oceans and getting a lot of fish out of there. And at the same time, we're also increasing plant productivity, which is something that you mentioned earlier, which can have also a positive effect on biodiversity. So there's a mixture of how humans are changing the planet in terms of climate, in terms of nitrogen availability. We're fertilising plants with CO2 in the air. Can we expect what you observed over long timescales? Can we observe the same effects of these factors, or is it all different and more complicated now with humans? Is there what can we learn from the past for what is happening now?

00:16:44: Fritz: It's a very good question. We asked ourselves that very question in that paper. Right. And we actually compared the when we did this productivity, um, diversity relationship. So how much plant productivity do you need for how many mammals. There is a positive relationship. But if you put the present day data points on that relationship they are off completely from the line. So today we have a lot fewer mammals than we should have because speaking in geological terms, these megafaunal extinctions were very recent. They only happened 10 to 50,000 years ago, which is the blink of an eye if you measure the diversity in 1 million year intervals. Right. Yeah. Um, so maybe we're still in kind of the recovery from this extinction, maybe this speciation ongoing. If we let it run for long enough, there would be large mammoths again. They would just be more adapted to warmer environments. Probably. Right. Um, but the other factor that humans are doing. Yes, we're increasing plant productivity, but we're also taking a lot of it for ourselves. So there is a concept called human appropriation of net primary production, which is a very long word to say. We're taking nature's products for ourselves and for the domesticated animals that we have. So there's actually a lot of plant biomass today that is not available to wild mammals or to nature.

00:18:06: Hahn: Most of land area is used for agriculture and for grazing agriculture.

00:18:11: Fritz: Grazing is the most. And of course, if you think about forests, there's timber extraction. Yeah. Um, whatever. People get out of the forests otherwise. Right. So there's a lot of biomass not available, um, to these wild animals. We know that the biomass of wild mammals since prehistoric times has declined by 82%. I looked that up this morning to have this number ready, because I always think it's quite baffling. Um, so if you think of mammals, you always think of elephants, lions, tigers. But all of these actually form a very, very small proportion of the biomass on this planet. Only because humans and domesticated animals have more than ten times the biomass now than these wild animals have globally. So I think, yes, in theory, if you let evolution run long enough and you warm up the planet and you don't have a lot of climatic extremes, which is another thing that climate change is doing. In theory, if you have more tropical climates, you should get more mammalian species. But speciation events take about a million years in mammals. Maybe it's quite hard to know, but it would be a long time to wait for humans to get higher diversity on the global scale.

00:19:27: Hahn: Or our species will have to survive for a long time. Let's see. Well, we won't see. You also in your research looked at how climate is related to body size of mammals It's also over that long time period, like millions of years. What did you find there?

00:19:47: Fritz: Yeah. So it was kind of looking at the same fossil record, but with a bit of different data. We looked at species level because we really wanted to know about this body mass, um, how it works. Um, so the nice thing about the fossil record in this period 15 million years ago to 2 million years ago. Climate is kind of continuously cooling down. And what people have noticed a long time before we did in these papers is that most mammalian taxa tend to increase in body size. So, um, mammals get larger over this time period, basically. And it's a signal that is partly caused by, um, larger, um, the groups of mammals that have larger species, um, becoming a bigger proportion of the fauna. So for example, um, in those 15 million years, we have a lot of diversification of the taxa that contain bison and cows and deer And these kind of get much more species rich than the antelopes and the goats and the sheep. So you basically just have more and more, um, larger species because you have more and more of these groups that are larger. But it's also an effect that happens within a group. If you think of horses or, um, species of horse that is around today is very large. But 15, 20 million years ago horses were quite small, more like dog sized. So within the group of horses, we also observe that the larger species survive more and the smaller species go extinct more over these 15 million years.

00:21:17: Hahn: So apparently large body size is beneficial in a colder climate.

00:21:23: Fritz: Yes, that's the thought.

00:21:25: Hahn: And why is that?

00:21:27: Fritz: Um. It's because if you're larger as a mammal. So mammals are endothermic. We spend a lot of the energy that we take in to keep our body temperature to be independent of the outside temperature. And that means that the volume to surface ratio is quite important, because the more surface you have, the more heat you lose. Just because your body is warmer than the area around then the air around usually, um, and if you are have a larger body, then for the volume that you have, your surface area is smaller than if you have a smaller body.

00:22:05: Hahn: So it's easier to, to keep your energy with the larger.

00:22:09: Fritz: You lose less heat just by existing. Yeah, yeah. Um, you can observe this, uh, actually, large animals, uh, often have problems, um, getting rid of the heat. Right? So, for example, elephants don't have much fur. They have they still have hairs, of course, but they're not developed as a fur that's covering them because they need to lose their body heat somehow. Right. Otherwise they would overheat in the region where they live.

00:22:35: Hahn: Okay. We've talked, uh, almost exclusively about mammals. Now I want to switch to birds. One study of yours caught my attention, which is about bird migration, and I expected maybe you did too, before that study, that birds would migrate to places that suit them climatically so they would like historic would fly to Africa in the winter season because it's warmer there and probably what we would intuitively think. But it's not what you found. What did you find instead?

00:23:12: Fritz: It was it was quite interesting. Yeah. So in a way, this climatic expectation makes sense from a human perspective because of course winter is quite harsh, but it has always been a theory that it might be food availability rather than the temperature itself. Right. So if you think of storks, what do they mostly eat? Maybe it's amphibians in summer. They like that. At least in winter all the amphibians are buried in the ground, right? So they can't find them. Um, so it might not only be the climate. So we didn't quite start out from the point that you sketched, but yeah, it was kind of a the test was we thought if we compare the actual climatic niches. So we have the occurrence points where the species, um, occur in summer and in winter in the breeding season and in the non-breeding season, let's say. And we expected that when you go from your breeding habitat to your non-breeding habitat, you kind of stay in the same climatic niche, I would call it, in the same climatic environment, same climatic conditions. And when we actually statistically tested that, um, it was the case for going, well, if we do the European perspective for going south. So species that go from the breeding grounds in summer to the non-breeding grounds in winter, um, tend to have a more similar niche. But then for coming back it doesn't make sense. So they should be staying in Africa. If basically they shouldn't go back to Europe, if they want to really track the climate. They want the same climatic conditions through the year. Then it would make more sense to be in the tropics, where, of course the climate doesn't change much, but they do come back. So we think from this paper also that it's this food availability plays a role and it's really to profit. In our spring and summer, we suddenly have all these insects coming out and multiplying and making mostly many generations of new insects that happen in our summer.

00:25:03: Hahn: So, so those birds that do stay in Europe for or in Germany, for example, are birds that probably have a different diet because they they can find food in winter.

00:25:15: Fritz: They switch to more generalist diets. I'm not a huge expert on this, but I mean, you know that you can feed most birds with seeds right in the winter, and those birds tend to eat more. Many of those eat more insects in summer if they can, so they're more flexible somehow. We also found that the residents birds, the ones that stay, that don't go, Actually have a more restricted climatic niche through the years. So somehow, even though they stay, they pick the places where the climate is more similar in breeding and non-breeding season, which was quite interesting. I did not expect that.

00:25:52: Hahn: Yeah. So you did, uh, connect places where birds live with, with the climate and you also looked into the future. So you're actually looking at long timescales in the, in the past. And you look at what birds are doing nowadays, but also how they might change in the future, and in particular how how bird diversity might change in the future on a warming planet. And those are, of course, simulations done on a computer. So there's always a uncertainty associated with that. But what did you find in that in that study?

00:26:33: Fritz: Yeah, it's a very hard study to explain because it was such a big global picture. Um, it's so the principle is similar. Like the migration thing, we took the occurrences where the species are today and we know the climate that that represents. And then basically we have from this international, um, Intergovernmental Panel on Climate Change, the IPCC, we have the scenarios of what the climate will be in the future. So you can model where the bird occurs in this in today's climate and then project where is this climate going to be in the near future. And I think we did something like 50 and 70 years intervals and different scenarios of climate change because of course, humans human decisions influence how much the climate will change, right? Um, and overall, what you find is that, um, what previous studies have shown that, of course, there are actually large areas on the globe where you will get an increase in diversity, Especially in the northern latitudes. So it's in Germany, I think it's divided between northern Germany and southern Germany. Southern Germany has a higher net loss of species. Northern Germany has a higher net gain of species. And that is because in our region, in Europe and especially in northern Europe, if you get warmer temperatures, that means that species can move in that have further lived further south so far, and they can just move north. Um, but that is assuming that they can actually move. And then the interesting thing in this paper wasn't looking only at this net gain and loss. So overall we might be gaining species, but we were we were interested in what kind of species we actually gain and lose. So we, um, differentiated which species get lost from the local community, which species get gained into the local community. And then for each of these two components, we looked at how closely related are these species to the species that are that are already there, that don't change. And what you find is that you have quite a lot of places on Earth where species richness is increasing, so you're getting more species like in northern Germany and Scandinavia. But they are mostly species that are very closely related to species already there. Basically, we might get, I don't know, more sparrows or something. Right. So species where close relatives already live in the community. And because this is a computer driven scenario, of course we have no idea what actually happens. Will they actually be able to move in or will that cause more competition for the species already there? And then of course, the whole ecosystem might change if you switch one sparrow species for another. What consequences would that have for the seeds that they transport for plants, for example? So it was a very rough simulation, a kind of what if scenario. And the interesting thing is that those areas that gain species mostly gain Again the very close relative. So it's not very exciting. We're not gaining. Exciting tropical cool species, let's say. And then in large areas in the tropics, there is a net loss of species. And those that get lost from the local ecosystems tend to be the ones that are have fewer relatives. So they are more unique. And quite often how close birds are related to each other also reflect somehow what they do in the ecosystem, right? So close relatives tend to do similar things. They tend to, you know, all eat fruit in one group of birds, or they all eat seeds. And then if you lose species that don't have close relatives, they might be doing very unique functions in these ecosystems.

00:30:14: Hahn: That's fascinating. And uh, also as you mentioned, the many uncertainties involved. But I think that's that's what we should always keep in mind when we do predictions about the future, especially in such a complicated socio ecological system. Like. Yes. Like humans and biodiversity. It is. It is really complex. And we can only.

00:30:40: Fritz: Well, there are a lot of assumptions we have to make. Like how far can a species actually move within one generation. Right. That is the most is the assumption we thought about most. And then things like how species interact or how much the birds would depend on specific plants that are there. We couldn't put in there because we modelled all birds, 8000 species across the globe out of 10,000. And it's a very rough spatial scale. So people on television asked me like, what is going to happen in Frankfurt, a mine where I worked back then, right? And I said, well, we can't say that from those models because we model 100 by 100 kilometre grid cells roughly. So it's very large.

00:31:20: Hahn: Local communities can, can, can evolution also have an effect? Do we have evolution which can kind of also help species adapt to to a new climate.

00:31:33: Fritz: That's the hope. Yes, we hope that that can help a lot. And there are some interesting studies, mostly done in labs. So they had to do with birds. But people do that on insects a lot. How quickly can species actually adapt to warmer temperatures. And some things in in your metabolism can adapt very quickly, like stress hormone levels and so on. Um, other things might be harder to adapt. And of course, it's always tricky to say how endothermic react, right? Because they have a bit of a different, um, system in dealing with outside temperature than exothermic.

00:32:08: Hahn: So one more factor of uncertainty. Yes. Okay. So this has been a highly, highly interesting conversation. Uh, to conclude, I would like to hear your personal view, given your very broad and long term perspective of how Biodiversity and climate have changed over time. And now there's humans who are massively impacting planet Earth. How optimistic or how pessimistic are you about our future and biodiversity future?

00:32:48: Fritz: Yeah, it changes currently, almost daily when I read the news, but overall I think I tend to be an optimist rather than a pessimist. And maybe that's also this long term perspective. So we know Earth has survived previous mass extinctions, so something will probably survive. But I do also think it might get very uncomfortable for humans. So the average recovery time from past big mass extinctions has been around a million years. So if we don't find food for a million years, we have a problem, right? And then, um, I tend to be optimistic also because all the scenarios that we do have for this ongoing climate change, for example, they tell us that we could still do political and social. Social decisions that mean we don't increase into the very worst scenarios, right? So there is still the potential to somehow change society in a way. Um. That we can reduce biodiversity loss and mitigate effects of climate change. And I do think there is still a potential to do that. But yeah. So of course shrinking. But as I said, I tend to be the optimist.

00:34:00: Hahn: So you mentioned these mass extinctions. Some people argue that we are already in now in the six mass extinction that we're experiencing. And we're also humans are also the reason for it. There are others saying that, well, we can't say yet because previous mass extinctions happened over a much longer timescales. And, um. What is your take on that?

00:34:27: Fritz: Um, both sides have some arguments, but I think, oh, yeah, I do think that extinction rates are higher today than they should be. So I think we are in a mass extinction, but we don't know yet how bad it will be, because there's also a lot of things we're still learning about how extinction works and how many species still hang on in small populations. But then if something very small changes, right, that whole population goes extinct. So, um, I think we are in a mass extinction, but that's a very personal take. I think most scientists would answer that like that. Of course, Earth has come through previous mass extinctions, but as I said, it wasn't fun. Like, um, if you have to wait a million years until there's enough biodiversity for functioning ecosystems, like after the worst mass extinctions, you basically only find one type of muscle that survives on very anoxic things in the ocean, right?

00:35:24: Hahn: So okay, hopefully we will not go that.

00:35:28: Fritz: Far.

00:35:30: Hahn: To end. I would I would want to ask you, can you briefly summarise what, from your point of view, are the most important messages of this conversation? What are the things that you you would like the audience to remember in, let's say, two weeks from now?

00:35:50: Fritz: Um, that's a very hard question to ask a scientist, because we always get lost in the detail. So, um. I think my main interest and what I think is coolest about this research is that if you look at across these long timescales, you do get a different baseline for our present day world, right? You understand how the earth, how mammals, how birds might have functioned without humans, how ecosystems would have worked. And you could put into perspective how much humans change this. But it also offers maybe some solutions of how we can mitigate that. The changes won't be so bad, right? Especially if you're talking about climate change. Extinctions from climate change that are happening today are actually still on a global scale. We have quite a few globally extinct species from human climate change so far, but we can look to the fossil record where this happened quite a lot of times. Right. So we can learn about the future from the past if you want. I think that is, um, yeah. Why I'm mostly fascinating and fascinated by these long term scales.

00:37:01: Hahn: Yes. And it was a fascinating discussion. Uh, also for me, I learned a lot. Thank you very much, Susanne. I hope you enjoyed listening to this conversation. Be sure to follow us on X, on Bluesky, on LinkedIn, and on your favourite podcast app. For feedback, ideas or questions, use #InsideBiodiversity or email us at podcast@idiv.de.