Is Biodiversity Declining Everywhere?

00:00:00: Dornelas: A simple narrative that says everything is going down. Is much easier to sell than a narrative that says, well, actually, that's not exactly true, that some places are improving and some places are becoming worse.

00:00:21: Hahn: Welcome to Inside Biodiversity. 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. In today's episode, we will focus on a question which is at the core of biodiversity research. How is biodiversity changing? My guest is Maria Dornelas. Maria is a professor at the University of Saint Andrews in the United Kingdom and at the University of Lisbon in Portugal. Her work has challenged some of the prevailing views about biodiversity change. Welcome, Maria.

00:01:00: Dornelas: Thank you very much for the invitation to be here.

00:01:03: Hahn: Let's start off by you telling us briefly who you are and why do you research biodiversity change?

00:01:12: Dornelas: So I am a macro ecologist, and about ten years ago we started assembling a database of biodiversity time series called Bio time. And then we started extracting trends from that database. And much to our surprise, when we first started doing it, I very much thought that I was going to be talking about losing mammals faster than we're losing plants or something to that. Um, similar to that. And instead, what we found is that biodiversity, temporal trends in biodiversity are much more complex than I was anticipating. And there's rather than finding systematic loss everywhere, we see mixed trends with some increases and decreases and some remarkably stable trends in, in, in the numbers of species that we see in any one place. It took us maybe two years to actually trust those results and publishing them. And when they were published, they were fairly controversial. But I would say that they've held pretty well, and it's now been ten years, and I don't think very willing to be persuaded otherwise. But I don't think I, I don't think anyone has shown that we were wrong in, in that pattern. So it's just turned out to be much more valuable than we thought it was going to be in terms of the numbers of species that we see in any one place. But at the same time, what we also found is that there is really extraordinary change in the identities of the species that we find in one, in any one place. And so, like one of my hobby horses at the moment, is that I really think that we should be talking about biodiversity change, rather than just talking about biodiversity loss.

00:03:06: Hahn: Your work is cited a lot in the context of what is called the biodiversity conservation paradox. Can you explain to us what that paradox is and why it's paradoxical? What is paradoxical about it?

00:03:23: Dornelas: Well, the paradox comes from the realisation that humans have undoubtedly changed the planet in really substantial ways. And we know that a lot of what we do to this planet from, you know, climate change and land use change and different extraction activities is typically not great for biodiversity, quite frankly. And so how do you then reconcile that knowledge with also the observation that at least since we started seriously monitoring biodiversity, we don't detect declines everywhere. I'm also puzzled by this. I think I don't have an answer to, and I think from a purely scientific point of view, then that's kind of cool, because it means there's more questions to ask and more things to understand. But my personal bias is that I also care a lot about the environment, and I care a lot about biodiversity, so much so that I've devoted my life to studying it. And so I definitely don't want to be misinterpreted as the person who said everything is fine and there is no biodiversity crisis, that is very much not what I'm saying. Just to be clear, like in addition to the macro ecology side of my work, I also do fieldwork and my fieldwork is on coral reefs, which are kind of like the poster child for an ecosystem that's not doing great, especially with the marine heatwaves that keep causing huge mass mortalities. And so, just to be clear, like my personal experience like that, the data set that I've collected, I've witnessed a long term study site having an event where we had 98% mortality and that's, you know, really sad. Like I have a very strong emotional response to this, a very strong emotional attachment to these places. And so I do not want to downplay biodiversity loss where it happens. The thing is, that's not the only thing that happens. We also see often remarkable paths of recovery. And the other thing that is that we've increasingly realised is, is that biodiversity change is incredibly scale dependent, for example. So you can have sort of losses at one scale and guidance at another. Also like the key to to this, I think, is actually related to the compositional change that we're witnessing. So, so, so we often have replacement of species. And that's a much stronger signal than just the loss of species or just the gain of species.

00:05:59: Hahn: So I wonder. I mean, you also said you are puzzled and you don't know really what the drivers are that explain what you're observing. I wonder, in an undisturbed habitat, would there also be this species turnover so that the identity of the species changes, but the overall number might might remain the same? And do we know if that's the case? How much have humans changed that process? Have we accelerated this so-called temporal species turnover?

00:06:38: Dornelas: Well, I'll start by saying that I think currently there are no undisturbed places on the planet. Right? We have seriously, seriously changed it. So even, um, even in a deep ocean, you can find plastics. And, you know, because we've done climate change to the planet, even where you don't have humans physically going to, um, I think we currently have an undisturbed place on the planet. So that's the kind of sidestepping your question a little bit.

00:07:04: Hahn: Makes it harder.

00:07:04: Dornelas: To see.

00:07:06: Hahn: What is the effect of humans.

00:07:07: Dornelas: Exactly. It's not it's not obvious is it? So to think about, think, think carefully about the effect of humans on the planet. Then we have I think we have to use much longer time scales than we have just normal biodiversity, more than biodiversity monitoring for because increasingly clear that human modifications of the planet are much older than we thought. This work coming from Earl Ellis, that shows that as far back as 12,000 years ago, there's really prevalent land use change in many parts of the world. There's also evidence that land use change is not being unidirectional. Right? So there's like sometimes we clearcut forests at a times you have sort of farmland abandonment and you have forests grow back. So this idea that we have that we've only changed the planet in one direction, I think is also part of why we see this variability in this complexity and biodiversity trends. What I really wanted to point out is that we I think we need to use sort of longer time scales, and we need to tap into our paleo colleagues to, to to do that. And then it becomes challenging because the types of data that you have are so different, but also really interesting. And in terms of of figuring out how have rates changed in the history of life, not just the the very recent past, but like more broadly and what is natural and not natural?

00:08:41: Hahn: So it's it's yet not possible to disentangle that so far.

00:08:46: Dornelas: Um, well, I'm excited about work that's being done in this, in this area. I think it's an open question, I think, but I think there are exciting things coming in, including from work groups here at IGF.

00:08:58: Hahn: So You said that your study was, uh, picked up by your fellow researchers as well. It was controversial. Can you tell us more about the reactions to your study? And why was it so surprising? How did did they react?

00:09:18: Dornelas: I would I mean, it was definitely controversial, I would say, but I think reactions were mixed with some people suddenly going, oh, I actually see that pattern in my own data. And I thought I was weird. So thank you for it. So there was one element of people suddenly recognising their pattern, the pattern that they've seen in their own data as being part of a bigger pattern of change, more than just loss. There were other people whose reaction was like, uh, if you say that, then you're undermining the conservation movement because you're sort of making the point that there is no biodiversity crisis. And again, I want to say very clearly that it's not like I never said that there was no change in biodiversity, only that change in biodiversity is sometimes losses, sometimes gains. I've increasingly started questioning, partly from sort of look at sort of looking at work that other colleagues are doing on invasive species, for example, whether, you know, are all biodiversity gains good and are all biodiversity losses. But increasingly, my position is that good and bad are value judgements. And and they're very much not my area of expertise because I'm an ecologist and good and bad, I think are in a realm of psychology and sociology and, you know, good and bad, for whom becomes the question as well. And again, I think that's probably complexity there as well. So yeah.

00:10:49: Hahn: Yeah, yeah, yeah I think that's that's highly interesting. And uh, leads me to different question when, you know, when we, when we talk about this, what is the best term We should use for when we talk about what's going on in the world with biodiversity, is it a crisis? Is it a Armageddon? Is a just change. What is a good word to use?

00:11:15: Dornelas: Um, oh, this is probably probably make me really unpopular, but I think the most accurate description of current biodiversity change is actually nuanced and complex, which I know is a challenge from the point of view of communication, especially when there is a sense of urgency. And we know that the pace of change of the planet is increasing. And so a simple narrative that says everything is going down is much easier to sell than a narrative that says, well, actually, that's not exactly true, that some places are improving and some places are becoming worse. Or at least that's what I thought initially. One thing that I am increasingly aware of as well is that actually the conservation movement has matured. I like this kind of very, almost silly example. So when I was a teenager, being an environmentalist and having certain eco conscious was made me kind of weird. I was not there was not very common. And when my kids started nursery, they had to take turns at being the eco person in the room because it was such a popular thing to do. And so the conservation movement has really made huge progress. And maybe because I'm an optimist, sometimes I think that at least part of this signal that we don't have losses everywhere is actually coming from there. So we have changed things like we have. We started managing fisheries differently. We started managing in Europe, for example, many EU regulations were have been enforced that have made clear impact on water quality or on, you know, protecting habitats like we've expanded protected areas massively. We're not done right. There's a lot more to be, to, to to be done. But I'm hopeful that at least part of this new ones change in biodiversity is coming from the places where we've done better than we have done in the past, and I wonder if we don't talk enough about the successes of better management of biodiversity and better management of these of this planet. So I don't think necessarily that the narrative that everything is getting worse is, uh, well, I don't think it's truthful. And then I don't think necessarily that it is. It might be simpler, but I don't think it's necessarily better. I actually think that narrative of hope is also important and potentially effective, potentially more effective. And I, I wonder if like one of the things that the biodiversity world needs to do is to look at what's happened to climate change and not repeat the same errors. Right? So so there has been like this shift in the climate.

00:14:10: Hahn: Can we talk? Can we talk about climate change. Yeah. Later. I think that's that's very interesting. But I think you've made it very clear that you're not saying and your research doesn't show that, you know, there's nothing to worry about. Instead, it's nuance, as you say, and it depends on where exactly are you looking. Right. So really just looking at the average, um, what is happening may not be that helpful.

00:14:42: Dornelas: Agreed. I think we need to look at the variability in trends. And and I think that's potentially really useful because then it also helps us create priorities. Right. We can't do everything. What should we be focusing on. And then, you know, there'll be different strategies for what to focus on. And we can think about sort of proactive versus reactive strategies, where the proactive ones are the ones that identify the places that are doing great, and then and then prioritise those as the things that we want to maintain. Or you can have reactive strategies where you go, where you identify the places that are doing worse and prioritise improving those. And probably, you know, the smart thing to do is to do both or to do you have a strategy that has a combination of these two things. But focusing, I mean, the mean is an abstraction that doesn't actually exist. And to some extent, like what's happening on average is useful from a communication point of view. But is it the right, especially if the average is not super informative, but and, and the variance is much more so.

00:15:49: Hahn: But there are but there are some, you know, there were also some pushbacks and some people saying it. It can't be true or let's say more general. There were some criticisms on your study? What were they? What are the the other like perspectives on this issue?

00:16:06: Dornelas: Yeah, some of the criticisms are I want to start by saying actually quite valid. So one key criticism that often comes up is that, like most of our temporal horizons are probably too short to to include when many of the changes have happened.

00:16:23: Hahn: So so how long were the time series that you looked at?

00:16:26: Dornelas: So the the database stretches from the late 1800s to the present, but really the overwhelming majority of the data is from the past, you know, 40 to 50 years. And my response to that is that we've seen an acceleration of rates of change in this period. And so in principle, you should be like this is a period of time that we really care about. And also my other response is that we don't have a time machine. So to some extent we're kind of stuck with the data that we have because until someone comes up with a time machine.

00:16:58: Hahn: And another criticism was this the so-called lifeboat effect.

00:17:02: Dornelas: Mhm. Yeah. So the other criticism that comes up is that like our data is incredibly biased in all kinds of ways. Right. So it's it's taxonomically biased. It's spatially biased. We definitely don't have.

00:17:15: Hahn: So it's not representative.

00:17:16: Dornelas: It's not representative.

00:17:17: Hahn: Of what is going on in the whole world.

00:17:19: Dornelas: And this becomes especially important once we become aware of the variability. Right. So if we had a homogeneous change, it kind of it wouldn't matter. Right. Like whatever you sampled would be representative of when you don't when you have this variability, then you know, it really matters where you have sampled, where you have and you haven't looked. And so, for example, I'm very keenly aware we don't have enough data from the polar regions. We don't have enough data from the tropics either. So that's one of the things. So one of the some of the work that we've done since has been sort of focussed on quantifying, like the geography of biodiversity change. And there's definitely patterns there. So I think improving our the representativeness of biodiversity monitoring is super important. And I think. I really think that this is where we need a global approach to this, because some of some of the places where we don't have observations or where we don't have wealth. Um, so, you know, in poorer places and where you have fewer scientists, you have those are blind spots. And then the other places where we don't have observations, where is where humans don't go because it's too deep in the sea, for example, or because it's, you know, too cold or night-time or whatever. So I really think we need a global approach to that if we want to end up with a more representative. And I would love to see that. And also, the time to start doing this is 50 years ago when the second best time is now. Yeah.

00:18:56: Hahn: So to to summarise that, How contested are these findings of of yours? Does everyone agree by now that what you found ten years ago and of course, more recently also you continued that work? Is there a consensus or is it still very contested?

00:19:17: Dornelas: I would, uh, I don't know. You're asking the wrong person here. I haven't changed my mind. And just to be clear, my kids say that I'm, like, continuously the devil's advocate. I'm quite open to to to change my mind. And I've yet to see evidence to the contrary of what we found.

00:19:37: Hahn: Okay. I, uh, so we talked about climate and I interrupted you. Um, what do you think have been the most blatant errors in climate communication?

00:19:51: Dornelas: Oh, that is a very loaded question.

00:19:54: Hahn: Yeah, but we try to make it short. What's going wrong in climate communication?

00:19:59: Dornelas: Okay, so there's a meme going around somewhere that says that, you know, here are the steps of of of climate change denial. Right? So the first it's not happening. Second, it's happening, but it's not us. Third, it's us, but there's nothing that can be done. And when you realise that, yes, there's stuff that can be done, it's too late. And so like the outcomes of all of these are let's do nothing. So one of the things that I think we can do better in biodiversity communication is not fall into that trap. It is not too late. To take one example, we know and have known for a while now, that extinction rates in the recent past are really high, so they're higher than they have been.

00:20:42: Hahn: On a global.

00:20:43: Dornelas: Level, on a global and the global scale. Extinction is global, right. So so you know, and like I talked about how diversity changes scale dependent. You can have global loss without having local loss because there's so many species on the planet. They can just redistribute themselves. Right. So that's one of the reasons why we think we see the patterns that we see. But at the global scale, although this is really difficult to estimate, but like as far as we know, extinction rates are elevated. So much so that for a while now people have said they were potentially in the middle of a mass extinction. And this one is caused by human actions. It doesn't follow from that that this mass extinction needs to happen just because you have to keep the current extinction rates for a really long time to have actually lost.

00:21:33: Hahn: Like thousands of.

00:21:33: Dornelas: Years. Yes. So it's not too late, is is, I think, one of the things that we can do better from the point of view of communicating on the topic of biodiversity change.

00:21:45: Hahn: So be more optimistic and or, as Hans Rosling said, probabilistic.

00:21:51: Dornelas: Yeah, I love hospital. Thank you. And I am definitely, definitely a possibility.

00:21:55: Hahn: But okay, we're slowly coming to the end. I know you've talked about it, but could you please summarise the essence of what we know? What is going on with biodiversity on this planet, with a few sentences in plain language for, let's say, a public audience?

00:22:18: Dornelas: Biodiversity change is scale dependent. What is happening on the entire planet is not necessarily what is happening at any one place. And what I think we know now is that at the local scale and any one place, there are divergent paths of, of of biodiversity. So although we see change almost everywhere we look in terms of the identities of the species that we find. Some places are net winners of these change. So they're gaining species some spaces, some places are net losers in that they're losing species, and some places just have a constant number of species. Um, and yeah, I think maybe that's my summary.

00:23:06: Hahn: Okay, great. I mean, we've talked about many different aspects of your work. What would you like your audience to remember in a week from now from this conversation?

00:23:24: Dornelas: Embrace new ones. Overly simple messages are possibly not true.

00:23:35: Hahn: Very good. Thank you very much, Maria, for this very interesting conversation. Thank you for listening to Inside Biodiversity. Make sure to follow us on LinkedIn, X and your podcast app. For feedback, ideas or questions use #InsideBiodiversity or write us an email at podcast@idiv.de.