Is Biodiversity Loss Always Bad?

00:00:00: Chase: When we chop down an old growth forest, we get more species. You know, the the idea of local diversity going down actually doesn't make sense. When we think about basic ecological theory, humans are changing the environment. There's no doubt about that. But biodiversity doesn't have to go down. And we've created this idea that biodiversity is good. And when biodiversity goes down, it's bad. And from an ecological perspective, that doesn't make sense.

00:00:32: 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 and my guest today is Jonathan Chase. Jon is head of the Biodiversity Synthesis research group at iDiv and he's also a professor at the Martin Luther University Halle-Wittenberg. The main topic of his research is biodiversity change, and this will also be at the center of today's conversation. Welcome, Jon.

00:01:05: Chase: Thank you very much. Fun to be here.

00:01:07: Hahn: I'd like to start by you telling me and the audience, what motivated you to become a biodiversity researcher and what keeps you motivated?

00:01:18: Chase: Biodiversity was never really a goal per se. I was interested in and plants and animals and their interactions in nature. So I became an ecologist. And then biodiversity sort of emerged as something that I became more and more interested in through time. As I was studying species interactions and how species responded to environment and anthropogenic factors and things like that.

00:01:41: Hahn: Okay. We'll talk about, uh, biodiversity and biodiversity change, both on the global level and on the local level today. I think one metric that is important in that context is species richness. Can you briefly define find what that actually means.

00:02:01: Chase: For me, species richness is is a great metric, but it also causes a lot of trouble because we can't talk about any measure of biodiversity, but especially species richness, without thinking about the window of observation that you're making. Are you studying a meter squared in a forest, or are you studying the entire forest? Species richness has a value for both of those scales, but it's completely different. And so but.

00:02:27: Hahn: But but just for understanding what it actually means, it just means the number of different species in that place, which can be a small place or a larger place. Right, exactly.

00:02:38: Chase: It certainly species richness is just a very simple metric. It's just the numbers. But the problem is that it depends on how you count. You count it in a meter or in a kilometer. Do you count it in the entire country of Germany or just in the city of Leipzig? These are very different things.

00:02:58: Hahn: Or you can look at it at the global level. And let's start talking about the global level. What do we know about the number of species or species richness on the global level. How has it changed. How is it changing or what's the uncertainty. What do we really know about that?

00:03:19: Chase: I mean, this is something that very few people really quantify. Well, we guess how many species are lost. We know how many species have been lost based on the identification of certain species that we know very clearly went extinct. You know, these are the classic examples of species that have gone extinct over the last several hundred years due to usually human intervention. But then we use background rates of guesses about extinction rates to talk about how many species have likely gone extinct. And those estimates can be highly variable. And so there's still a lot of doubt even though we like to see these really clear numbers of the rates of extinction per day or per year, per 100 years. We talk about this sixth mass extinction that we're part of. But the evidence for those numbers are often with huge errors around them.

00:04:17: Hahn: So there there have been some papers that claim that, uh, current extinctions are about at least for vertebrates, I think are about 100 times higher than the background rate, which would be like the natural extinction rate without human influence. How high is the uncertainty regarding that number?

00:04:41: Chase: Well, I mean, the uncertainty is really about the understanding of what background extinction rates were. So what we the papers that you're talking about have good estimates of current extinction rates, um, at least to some degree. The question is what were background extinction rates? And these are things that we can infer from the fossil record. We can also use other kinds of modeling tools to guess at what those extinction rates are. And I absolutely agree that those guesses are pretty likely to be true, that we are in a phase of extinction rates that are certainly higher than often background level, background level. Of course, it's highly variable depending upon what the conditions on the Earth are at a given time, but I don't think that's strongly disputed that we're in a in a phase where extinction rates are pretty high.

00:05:36: Hahn: And it's also not disputed that this is due to human activity.

00:05:42: Chase: I think it's pretty clear that especially I mean, when you really think about it, many of the the most egregious problems occurred when humans first started moving across the planet And we lost a lot of, you know, huge, fascinating creatures. Uh, large mammals and, um, things like that that we, we know were pretty clearly at the hands of, of some of the first human colonists. And so those extinction rates usually included in a lot of these more recent estimates, where we're talking about the last few hundred years. And so if you add those in. Yeah, clearly humans are are changing the planet in dramatic ways. More recently it's it's more difficult to quantify. And I think more importantly, you know, you say it's just a few hundred species and in the end, it is just a few hundred species that we can document have gone extinct.

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00:07:32: Chase: You know, you say it's just a few hundred species, and in the end, it is just a few hundred species that we can document have gone extinct. But those were really important, interesting, valuable species in many ways. And having lost those changes, the dynamics of the planet.

00:07:51: Hahn: Talking about documented extinctions. It seems like that many of those extinctions that have been documented, which is about nine, about 900 species, according to the numbers that I saw. Many of those occurred on islands, large and small islands. Is that true? And if so, what's. What's the reason for that? Why have these documented extinctions mainly happened on on islands?

00:08:22: Chase: Yeah. I mean, that's clearly true. Those, um, there's many reasons for it. Many of the species that live in a more mainland environment typically have larger range sizes. And so even though their populations have, um, seriously declined, the the actual end game of extinction hasn't occurred. That doesn't mean that they aren't locally extirpated or driven extinct from certain places. There may be just a few of them, Handfuls of them left in botanical gardens and preserves. But they're still there. They still exist. Islands are a whole different story for two reasons. One is that they are unique. They have these endemic species that have colonized and evolved over millions of years and only live on these islands because they've adapted to the conditions of of these islands with no, um, in and out dispersal. And so you get these very unique species living on islands, and they've evolved in the context of the island and the way it was before humans colonized. And so it's very easy for these, these species that were perfectly well adapted to the environments, to have no ability to deal with the changes that happen as humans come in. There's just, you know, tons of examples. One of the most interesting to me is in Hawaii. There are huge diversification of birds that we don't even know about. If Darwin had gone to these islands, he would have probably developed his theory on the these honey creepers in Hawaii that diversified in amazing ways. But they disappeared when some of the first ships came to the islands, and they had mosquitoes that were present in the on the ships. These mosquitoes didn't live on Hawaii. And so these mosquitoes also were able to bring diseases to the birds. And the birds had no ability, no immunity towards these diseases and just wiped out entire diversification of species. And so, you know, in Hawaii alone, you're probably looking at several dozens of those species. Of those 900 documented species are right there in Hawaii having gone extinct. And also many other groups of organisms that we know went extinct on places like Hawaii and some of these really unique environments, because we come in and we changed it, and we changed it in a way that those species had evolved for millions of years, had no ability to deal with those changes.

00:10:58: Hahn: So there were no no parts of the population that could escape to other places on these islands. And that's why they were why more of them became extinct on islands while on the mainland. Some of them might have survived in small parts of the continent. Which means that if a species goes extinct on an island and it it only lived there before then, it's also globally extinct. And that is a bit different on the mainland. So let's talk about local extinctions and about local species richness. About ten years ago, there were a couple of studies that looked at local species richness in different places across the globe. And, um, They didn't find declines everywhere in species richness, so the number of species in many places increased, many places decreased, and in many it stayed more or less the same. What they found almost everywhere was that the identity of species changed, so the composition changed. Was that surprising? To the to the research community back then or what? Or was it just what people researchers expected to find?

00:12:24: Chase: Yeah. I mean, this is interesting because I was actually a reviewer, you know, in peer review, these papers often get reviewed before they're published. And I was one of the reviewers on on both of those papers. And I really had a mixed feelings because on the one hand, it was surprising we had built an entire set of ideas based on the idea that we're in a biodiversity crisis. And we didn't again really think about the scale problem. And so if species are going extinct globally, they're going extinct locally. And we just felt like there should be some proportional loss across those scales. And that really even set up some of the the current research programs, like the role of biodiversity and ecosystem functions and services, those are predicated on the idea that local biodiversity is declining. It just made sense. But actually from an ecological perspective, if you forget about conservation and you just think about basic ideas and biodiversity maintenance, things like the theory of island biogeography, which we've had for 40 years, these theories predict that we shouldn't expect a lot of change at local scales. We'll see a lot of turnover. We'll see shifts in species which species out there.

00:13:37: Hahn: So sorry to interrupt. So turnover means that they're different species than they used to be.

00:13:43: Chase: And this in this particular case turnover means through time that there may be one species in in a few years, but then it's replaced by a different species. Yeah. And when we think about, especially in the context of, of humans in the Anthropocene, we know humans are actually favoring this concept of biodiversity in many places. When we go to a desert, when we chop down an old growth forest, we get more species. You know, the the idea of local diversity going down actually doesn't make sense. When we think about basic ecological theory, humans are changing the environment that there's no doubt about that. But biodiversity doesn't have to go down. And we've created this idea that biodiversity is good. And when biodiversity goes down, it's bad. And from an ecological perspective, that doesn't make sense. And I think that we kind of backed ourselves into a corner by creating biodiversity as this, this, this Entity that that emphasizes good. You can have huge levels of biodiversity and habitats that are strongly degraded by people.

00:14:57: Hahn: Okay. If I understood you correctly, you said that if let's say you have a pristine forest and you chop down, let's say you build a road or you, um, then you might have an increase in biodiversity and the number of species. Is that right? And if so, why would that happen? Why would you expect that?

00:15:17: Chase: Sure. I mean, you know, again, we've known about this for decades. Um, Joe O'Connell in the 70s called this the intermediate disturbance hypothesis. Um, and it's a very obvious idea that there are species that actually are adapted to living in disturbed habitats. And there's many of them. Think about the dandelions in your lawn or all of the weeds in your garden. These things get in within days. They grow like crazy. They throw seeds out and they continue the cycle. They're really happy and disturbed environments. And there's many, many of these species that make a living living in these ephemeral, disturbed habitats. And so the idea of the intermediate disturbance hypothesis is if you're in an old growth forest, you've got these strong competitors, these trees that are really just knocking everything down, taking all of the light. And there's very few species that can do this very well. So diversity is actually quite low, even though this habitat we often think of as a very high quality habitat. We go in there and we chop down the trees and all of the weeds are just happy. They love it and there's a lot of them there. High diversity. And so again, creating this concept of biodiversity as a good thing has really created trouble because biodiversity is just a thing. It's just a number and it doesn't indicate quality.

00:16:43: Hahn: Yeah. So if you argue that high biodiversity per se is not necessarily good or bad, an immediate reaction could be. Well, what about the level of of an ecosystem being undisturbed or pristine? But there you might have similar problems. So I wonder is that even from a scientific point of view? Could you even is that something science can say? What is good or what is bad? Or what should we aim for?

00:17:14: Chase: We try. And there are, um, metrics that are being developed to try to deal with some of these issues, like the biodiversity intact in this index that some of our colleagues in the UK have developed. Um, the intact ness means what was it sort of before? Um, and that's useful. But then you really get into the question of what is before. Um, for example, you know, I grew up and have lived in North America for most of my life. And, and we view those ecosystems as the natural ecosystems and in parts of North America, like some of the great prairies and, um, and meadows, that you see, these open grasslands, those were maintained by Native Americans, those were created by Native Americans. And so what we say is natural is actually only natural. For the last several thousand years, since Native Americans came in and started using fire to manage the ecosystems. And so it really becomes a little bit of a question of what we often use. The word baseline is and is that baseline? What is it? Especially when we know global changes happen all the time, both historically and in current. And we know that humans have been involved in these ecosystems for many thousands and millions of years. So what what's natural is often a very difficult question.

00:18:39: Hahn: Another question. I mean, we've talked about Biodiversity change. Now we have mentioned also potential drivers. That could cause biodiversity change. So you've worked on a concept with Andy Gonzalez, who's also who's also interviewed in this podcast about detection and attribution. Can you briefly, briefly elaborate on that? What does that mean? And I think it's derived from a concept from climate change research.

00:19:13: Chase: Sure. I mean, detection is is what we've been doing for a long time. And what we've been talking about is simply the question of, is this measure of interest changing? And so for climate change, it's are there degree changes in temperature or precipitation. Detecting it and detecting that it's somehow different than it might otherwise be. And so detection is just looking for those numbers and detecting whether they're changing in a way that is clearly because of, you know, some difference through time. Attribution is the question of why is it changing? What are the drivers? And of course, in climate change research, the idea is is it due to things like greenhouse gases? Are those changes due to changes in the environment. And those are much more challenging statistically. But there's a huge field of of research involved in looking at things like causality, using things like, you know, these crazy words like counterfactuals, what would have happened under other circumstances. And we're developing these philosophical and statistical tools to try to get at that. And that's attributing the change. We often say, oh, that change happened because they chopped down that forest. Usually it seems pretty clear, but sometimes it's less clear and we need to go in and try to do those statistics and ask what would have happened if something different changed.

00:20:50: Hahn: So this concept has been used in climate change for for decades. Is is biodiversity research behind in that sense?

00:20:59: Chase: In many ways we are partially because biodiversity is still such a slippery concept. Um, and I feel maybe naively, as I'm not a climate change researcher, that that the measures of interest tend to be more clear in climate change research our measures. When we say biodiversity, we don't even there's the scale problem, but there's a biodiversity of plants, of microbes, of mammals. Um, all of these things are very different numbers. And so there is no biodiversity in the same way that there's a temperature or, um, you know, uh, carbon dioxide in the atmosphere. And so it is more challenging because we we're not seeing the same thing. Biodiversity is not one thing. It's a million different things depending upon how you define it. And that makes it much more challenging for us.

00:21:59: Hahn: So given the complexity of the issue and also let's say the the variability of of trends, especially on the local level, what would you suggest is a good wording when we talk about biodiversity change, which is the term that we've used now. But there are other terms around like biodiversity loss, biodiversity decline, crisis, apocalypse, armageddon, annihilation, ecosystem collapse and so on. So we can frame this in different ways. What do you think? What words should we use?

00:22:36: Chase: Yeah, I mean, a lot of those words that you brought up, they're dramatic and we loved them. And our titles of our papers and the the big journals. Um, and they're all very useful for talking to your, your family or the general public or the politicians. Um, especially because we want to convince people that there's a problem. And in order to realize there's a problem, we need to evoke drama. Um, and so, yeah, annihilation and Armageddon, those are just terrible words to describe some of these changes. Um, but we use them because we're trying to get a reaction. Um, and I know things like change are much less dramatic and maybe don't invoke, uh, some, some politician or some business person to spend time or money or change policies because things are changing. But if they're, you know, being destroyed and collapsing, those are more dramatic terms. So I can understand the use of those things. Um, but as a scientist, those don't have sort of mathematical definitions. I mean, how do you define Armageddon versus annihilation versus collapse? They don't, you know. And when does it happen and when doesn't it. There's no like number where you can define it. You can define some things like non-linearities where there's a slow decline and then all of a sudden there's a threshold where boom, there's a huge decline in whatever measure of interest. And those are important and dramatic, and those are involved in things like collapse or, or thresholds or tipping points, but you have to define them clearly and measure them clearly in order to really say something like that.

00:24:29: Hahn: So I guess the challenge is how do you craft a narrative that's short and concise and can be understood by non academics and people not involved in the field and at the same time is responsible in not misleading people. Like being being truthful about what we know. And, um, it's maybe a bit vague of a question, but do you have any do you have any suggestions on how we can communicate biodiversity change in a responsible, truthful, non misleading way?

00:25:07: Chase: I'm not sure I can answer that question because, um, it's a it's a it's a very challenging question because, because I do understand the problem. If we if we talk about nuance, if we use words or even math to describe these changes, nobody's going to care. They're not going to see it being a big deal. But if we we if we overdramatize it, um, then the at least as a scientist, I get Very uncomfortable. And some scientists that I know think that we should essentially deceive and use these words, because that's the only way we're going to get noticed. We're only way we're going to get our, our money and our our policy change. We have to be dramatic even if we don't truly believe it. Um, and that makes me uncomfortable. But I also recognize that the words that I use are really, um, too wimpy to have, uh, an effect on the policy floor. And to some degree, that's why I'm not on the policy floor. Um, it's something I. I've grappled with myself. I don't feel like I would be very good in some of those debates in the United Nations and the, you know, Committee for biodiversity and things like that, where people are trying to really affect change. And to do so, they need to convince people that there's a problem. And it's not very good to say, well, actually, I don't know if there are these kinds of changes and these kinds of metrics, but maybe we can look at it. So it's a non-answer. I'm sorry I'm not able to to find a clear voice for that.

00:26:53: Hahn: Yeah, but it's something to to think about. And of course, something that I, I think about a lot also because it's part of my profession and it's obviously you can have different takes on this. And I always find it interesting to hear those different opinions. I'd like to to finish this conversation. Can you please summarize what would you like the audience to remember from this conversation in a week from now? What are the key messages?

00:27:27: Chase: Well, I mean, to me, you know, we've created this term biodiversity. And it's useful in many ways. Um, but I think sometimes we can be too. Uh, we can worry too precisely about the numbers, and then we can sort of say, oh, is this changing? Is this changing? And we want to quantify it by 38% change or something like that. There is 100%, no question that every ecosystem on the planet is affected by humans, from the deep sea to the high Arctic tops of mountains everywhere you go. And we're changing those ecosystems and we're changing the species in those ecosystems, quantifying it. And some way that us nerds in the on our computers quantify it as useful, but it doesn't capture the change. And in the way that the multivariate way these changes are happening, they're changing in so many different ways. There's no way to capture that change in one concept or one idea, and I think maybe we're trying too hard to put numbers on something that the world is changing. Are we? Some of those changes are going to happen and we have to let them happen. But maybe we want to make sure that there's some parts of the world that are less influenced by human activities, that there are some species that still exist, that there are some ecosystems that still have the some sorts of intact ness, and that there are the services that these ecosystems provide, like, you know, for human health, for mental health, and for things like carbon sequestration. These things are critical. And biodiversity as a measure isn't necessarily capturing how important those things are. And so I think we just need to recognize that the planet is changing, and maybe some of that can be detrimental to those of us who live on the planet today. It's not detrimental to some other things, but it's quite detrimental to the way we've created our societies, the way we've created our, um, our political, our geopolitical dynamics. And when those change, when the, the, um, sea levels change, when water levels change, these have huge effects on the geopolitical system and our own livelihood and health. And we need to be aware that this is at as a result of our actions. And so we can try to minimize those in some places.

00:30:12: Hahn: Thank you, Jon. That was a very interesting conversation. Thank you for listening to Inside Biodiversity. Make sure to follow iDiv on LinkedIn, on X and your podcast app. For feedback, ideas or questions, use #InsideBiodiversity or write us an email at podcast@idiv.de.