How Much Are Humans Changing Biodiversity?

00:00:00: Gonzalez: Let's not oversimplify this discussion. We have to recognize that nature is complex, and that inherent beauty that we see and recognize in nature is changing in ways that it will be unrecognizable in decades to come.

00:00:19: 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 Andy Gonzalez. Andy is a professor at the Department of Biology at McGill University in Montreal. He researches how biodiversity is changing, causes and consequences of extinction and fragmented landscapes, biodiversity monitoring and biodiversity policy. In this episode we will focus on biodiversity change and the drivers causing it. Welcome, Andy.

00:00:57: Gonzalez: It's my pleasure. I'm very happy to be here.

00:01:00: Hahn: I want to start by asking you. Can you please tell us how did you personally come to. Um, to be interested in biodiversity and how did you end up becoming a person who researches biodiversity?

00:01:15: Gonzalez: I think I've been somebody interested in biodiversity since, uh, the youngest age. I really didn't know about the word biodiversity, of course, as a, as a young boy. But I spent many of my days in nature. I was fascinated with understanding where species live, how to find species, whether that was birdwatching, whether that was collecting bugs in a pond, uh, or wandering around at night looking for owls with a car battery and a headlamp. Um, I was just. I realized that I was very early on interested in how species related to their environment, whether that was something predictable. Could I go back and find species? Um, and so I without really knowing it. I was, uh, interested in how species interact and where they're found, and that was an enormous source of curiosity and satisfaction in discovering those kind of rules of ecology that we now I recognize later as a science. And the second thing was that I found I was always sketching and drawing in nature, that the act of observation was linked to to drawing and to to understanding, uh, what I could see, what I was observing and trying to put that on the page and then it would, I would paint or I would draw. And so that reinforced for me that, um, you could understand nature through several lenses to sort of a creative lens of drawing, but also as a scientist, the way we observe nature. So when I realized a little bit later that I could do that for a living, I knew that I want I wanted to be. In fact, I knew I wanted to be a zoologist early on when people ask me as a five year old, oh, actually, I want to be a zoologist. But now I realize that there is a more broad way of thinking about that. And that's what we would call biodiversity science today.

00:03:06: Hahn: And was the concern about biodiversity declining species going extinct? Was that also part of your motivation to go into that field, or was that maybe later.

00:03:20: Gonzalez: Much later? I think I, I can pinpoint a lecture I had as an undergraduate in the conservation biology class, where I was told for the first time what the background rate of extinction has been over millions and millions of years, and where our best estimates are for the 20th, the 20th century at the time, the late 20th century. And I remember being shocked that no one had really told me that. And so when I was confronted with those numbers, with the accelerated, um, rates of extinction, uh, due to human activities, then that's switched on the conservation biologist. And then I knew that I wanted to be involved in conservation science and how we can translate biodiversity knowledge into better, more effective conservation science.

00:04:13: Hahn: Okay. I will ask you a bit later about your view on how biodiversity is changing. But first I would like to talk about a couple of studies that came out about ten years ago, in your view, on on those studies. I know you're a critic of those studies and what these researchers did. They looked at time series of local species richness, which means that at different places they looked at the number of species present, uh, and how they changed over time and what they found caused some controversy in the scientific community. I would like to go through the results one by one and ask you for your your assessment on whether you you agree with these findings or whether you would disagree. One thing that they found was that the identity of species, like almost everywhere they looked, changed a lot. And the identity means that from the first point in time, when they looked to the second point in time, there were different species living there than before. So kind of the quality of the species community living there was changing almost everywhere in the world, or at least everywhere where they looked at. Is that something that you would agree with?

00:05:41: Gonzalez: I agree with the basic fundamental principle of all ecological communities that we see compositional turnover, that the identity of species that we see in a species list for any given place on Earth is not static. Um, in fact, it's one of the defining features of biodiversity change is that not only the list of species that we see there is changing, but their relative abundance is changing that it's possible for a rare species represented by a few individuals to become abundant and vice versa. And so we recognize in the field now that communities are incredibly dynamic, and they're dynamic because they're responding to the natural environment and the fluctuations in the natural environment, the availability of resources, uh, the fitness of those different populations are responding to this, the dynamic challenges associated with other interactions with other species. The question is, to your point, are humans significantly accelerating the rate of the change in the identity of the species on that list? Are we accelerating the turnover of the composition of communities. And the answer to that, I believe, given the evidence that we see, is that the answer is yes to that. There is enormous amount of uncertainty because the the dynamics of compositional change vary from place to place on Earth. And of course, they vary with the type of species where those are plants, animals, microbes, etc.. So I remember very early on seeing that first science paper by Maria Danielson and friends, where one of the key findings was turnover and the rate of turnover increasing, and I. And that felt a reasonable conclusion to me. I thought that was an important finding of that paper.

00:07:40: Hahn: Yeah. You mentioned one aspect that I didn't stress enough that in these studies that we're talking about now, they only looked at which species were present. They did not look at how many individuals of each species were there. Right. So it's just the total number of species which is this metric is called species richness. Another finding, possibly more controversial, but maybe not, was that they found very heterogeneous trends looking at these different places on Earth. In some places the species richness increased, in other places species richness declined, and in still other places they were more or less the same. And maybe that was not totally expected by the community, because maybe, correct me if I'm wrong, maybe the expectation was that at almost every place, species richness would go down. So how do you see those findings? Are they valid or are you critical of those?

00:08:55: Gonzalez: This is um, a very important question. And those papers did something very important. They created surprise. They kind of shocked the field a little bit, uh, because I think we were starting to get to a point where a meta analysis is possible, that we were starting to see enough publications producing enough data to.

00:09:16: Hahn: Briefly say what a meta analysis would.

00:09:18: Gonzalez: Yes. Of course. Yes. So when we have a lot of evidence published in a number of studies, we can gather that evidence and pull it, put it, aggregate that information, and then we can begin to do analysis on the total totality of all those studies. So you might be able to create an average across many averages or calculate the variation across all studies. And that gives you the meta meaning, the kind of the average of averages, the conclusions from many studies. And of course, to do that well requires high quality data that it requires making sure we're comparing apples with apples, and that we're very careful about the units, the scales of space and time that we're comparing and that we have appropriate baselines or references. And so I don't think anyone was surprised with the finding that in some locations, biodiversity, maybe some measure of biodiversity, in this case, species richness is going up and in other places it's going down. That's no surprise to a community ecologist. What was surprising was the conclusion that this is representative of the global system. And so what the papers that I were involved that were criticizing or critiquing those papers is that, hey, we need to recognize that the data sets that are available in the literature that we can use to do the meta analysis have certain geographic biases. We sample species in certain locations on the planet. And in fact, the surface area of all those locations is much less than 5% of the Earth's surface. So we don't have a representative, geographically representative distribution of data, nor do we have a taxonomically representative data. So we're not looking across all taxa or even something that's representative of the tree of life, which is important. And then there are other biases for the sake of time. I'm not going to go into all those biases, but those are the two key ones. And and a secondary point. There was an immediate association with the role of humans and how land use change, climate change, pollution, invasive species may or may not result in a net change locally. And to answer that requires building data sets that have also collected the causal drivers, the things that drive change in species richness. And so when you're doing a statistical analysis, you want to be able to relate the change you observe and detect with the causes. And then you can say, ah, change in one direction or another is due to these underlying factors. And, and those early analyzes didn't do that.

00:12:03: Hahn: Yeah. We'll talk about uh, drivers of biodiversity, uh, change later. Um, so you say those the different sites that they looked at are not representative for the globe. I understand that criticism. Still, there were like thousands of different locations that they looked at. So just as many were showing downward trends as upwards trends. So I wonder is it wasn't that still surprising that so many of these maybe not representative areas were showing upward trends instead of downward trends?

00:12:41: Gonzalez: Well, it all depends on what you're referring, what the context is. For example, if you only sample communities that are recovering from intensive land use, for example, then you might expect for certain taxa to observe recovery. That would be a good thing. That would be an outcome of conservation action. And so you would expect that there's a distinction to be made between what is the inherent dynamic complexity of communities locally that we expect fluctuations, a richness to go up and down over time and those fluctuations. And then we're observing those fluctuations. And then then what is the so what is the expectation of that distribution of fluctuations up and down. So how many places is going up and how many places are going down relative to human impacts. But do humans shift the balance of up and down trends? And that is what we have not sufficiently established yet. Using the full complexity of of the data we have available and the methodological approaches that we can do to assess the uncertainty that we have about that.

00:13:55: Hahn: Mhm. Uh, another thing that I wondered about is that if you see that, okay, there are many places where trends are actually going, going up and others going down. Is it very important to know what a global average is or like if you want to do something about it, isn't that much more important? Like for every individual site to know how is the trend going? And as you mentioned, what are the drivers?

00:14:25: Gonzalez: Yeah. So this speaks to two issues. One is related to international policy frameworks. For example, the new Global Biodiversity Framework, which stipulates certain targets about recovering biodiversity. And of course because it's a global agreement.

00:14:42: Hahn: Yeah.

00:14:42: Gonzalez: And it's nation states that are committing to action. So the answer to your question is sort of at multiple scales countries how the How a country is doing. How a subnational units of a country, provinces, states, counties, etc.. And then how does action at those levels translate into a global outcome? So yes, we can assess the evidence that at the local scale, conservation action is leading to an adjustment in the in the frequency of of declines and increases. But others would say, well, actually it's the global rate of species extinction that matters. You know, are we pruning the tree of life in an irreversible way? Are we losing branches of the tree of life in an irreversible way? And that's where our primary focus should be. But if you're a conservation organization, you're very focused. I think we're focused legitimately on local and regional scales and addressing the causes of loss of biodiversity at those scales.

00:15:44: Hahn: So we've looked at these different aspects of these studies, which are also known under um, under the term biodiversity conservation paradox. By the way, why is it called paradox? What's paradoxical about it?

00:15:59: Gonzalez: What's paradoxical is that if we observe the state of nature, many ecologist would agree that large areas of the planet have been degraded, or we're seeing a change in the variety of life, the loss of biological diversity in a way that suggests they're no longer natural. Yeah, right. Pre-human impacts. But if you go in and measure biodiversity, if you take an indicator of biodiversity or a measure both like species richness, you may see no change. And so the the proponents of the conservation biodiversity paradox are saying, well, on one hand, we've got a measurement that says there's no change and that when we go into nature we see lots of change. So what's happening? Why is there a mismatch? That seems paradoxical.

00:16:43: Hahn: Yeah. So we've talked about these different, um, findings of these studies. Can you just very briefly summarize on what aspects of this, uh, biodiversity conservation paradox, where do you agree with the authors and what are the aspects where you disagree?

00:17:04: Gonzalez: Well, first of all, I think I want to say for the record that this is a very important chapter in, in biodiversity science right now, that the resolution of the debate, I think, has largely fallen on the shoulders of gathering better data, making sure that we have the appropriate framework for answering the question. So in my own research, I've promoted the idea of developing a discipline that allows us to assess biodiversity change in a principled way. And we call this detection and attribution. So we have to recognize that if we want to make comparisons among places, among countries, among regions, that we need to follow a standard protocol, a set of methodologies that not only detect the change that we've been talking about, but also allow us to be able to make a strong causal understanding with a statement of uncertainty. And that requires that we gather the data, we observe nature, we estimate the measures in this principled way. Now, of course, what we have in hand is what we have in hand. So the data sets we have are incredibly useful. And the sort of defining the biogeography of biodiversity changes is incredibly important, which means that we need to do it together collectively as a community in the coming decades. My feeling on the conservation biodiversity paradox is that that's a legitimate observation, that we need to be careful about how we quantify biodiversity. But we don't oversimplify the measurement of biodiversity because that risks oversimplifying the science to policy interaction. So when we're trying to describe biological diversity in a landscape, only using species richness is going to get us into trouble. Because what we value in biodiversity, what we think is important, has different dimensions to do with evolutionary distinctiveness the variety of life, the interactions among species and how those species are evolving and how they're driving fluxes of energy and gases and matter, etc., etc.. So if we only look through one lens, the species richness lens, then we're looking at a very poor representation of a complex system. So there are two dimensions. Then one is we have to measure change in multiple dimensions. and we need to do a good job of identifying what we think are the reasons why that change is happening.

00:19:55: Hahn: You you just mentioned now this, um, detection and attribution, uh, approach that you are helping to establish in, in the, in the community. And you recently had a paper with Jonathan Chase from iDiv on this. What I find interesting about it is that this concept actually derives from, from climate change, where, um, climate researchers first try to detect a trend, for example, are hurricanes increasing in a certain area. And and then secondly, ask, well, if you find such a trend and it's not zero, can it be attributed to anthropogenic drivers like fossil fuel burning? Can can you use that that very same framework for biodiversity, which I think probably acts more on on a local level compared to climate change. Um, or do you have to make strong adaptations, uh, to make it, uh, applicable to biodiversity?

00:21:02: Gonzalez: Yeah, there's it's a fascinating parallel between climate science and biodiversity science, but we recognize the equivalent to climate in biodiversity. We will call macroscopic patterns of biodiversity. So large biogeographic gradients in the distribution of species, for example, you know, the gradient of bird diversity from the tropics to high latitude. And so you want the equivalent in climate science, in biodiversity sciences. Can we detect the impacts of humans on large scale distributions of diversity. So you only need to look at climate science, uh, impacts of climate change on the distribution of species to see that there are macroscopic patterns. We're seeing changes in the phenology of of different species of trees and plants, but we're also seeing species shifting northward. So yes, you can detect and you can start to do the attribution at this very large scale. But now what climate science is doing, because now it's established irrefutably that humans are driving climate change at the largest scales of globally. And over time, now they're trying to apply the detection attribution framework that generates the evidence that human caused climate change is changing the frequency of weather events. So local phenomena like flooding, like droughts, like heat stress, severe temperatures, those kinds of things are in the variability at small scales. Now that is the analogy to the local biodiversity change debate. Yes. How can we deploy a robust methodology that allows it to see if the the fraction of attributable risk that is due to human impacts is causing a change in the fluctuations of extinction or extirpation and colonization at small, smaller scales. So we mean typically we mean a region or a landscape or even down to a wetland or a forest. Now that is where me and my coauthors, John Chasen and Mary O'Connor, believe that there is a strong need for a detection attribution framework. And I'm going to say that I think we have been fairly slow in biodiversity science to develop a framework that everyone can contribute to, and within which we can establish the evidence. We need to say what the trend is, the magnitude of that trend, the uncertainty in those trends and whether they are consistent with the underlying causes, both positive and negative. Right. Positive in the sense that conservation action is leading to the outcome we expected. So the just to wrap up on this, the detection attribution framework really is about building the discipline and the community of researchers that are committed to developing the best evidence, the best body of knowledge that we have that responds to the policy need of the global biodiversity framework.

00:24:03: Hahn: I would like to jump to a different topic that is also at my heart because I'm responsible for communication at IETF. I would like to hear your opinion whether biodiversity scientists are in general, doing a good job in communicating their research findings or what could be improved.

00:24:29: Gonzalez: This is a great question, and I think evidence suggests that if you look at the the number of articles in the media about biodiversity versus other causes of environmental change, like climate science, we can see that biodiversity gets less coverage.

00:24:45: Hahn: Yeah.

00:24:46: Gonzalez: Now, is that the fault of biodiversity scientists? Maybe. I'm not sure that we do the best job of conveying not only the evidence and the science, but also telling the right story, the right narrative. So I think our field has been largely about conservation in the face of kind of the collapse of, of ecosystems and the permanent extinction of species. And that's quite a negative storyline that was probably necessary for the most of the 20th century to establish what's happening. So the underlying narrative that runaway human exploitation of natural ecosystems to meet a growing economy, an economy of high consumption, is not compatible with a very species biologically diverse biosphere. But if we're going to switch gears now, I think we need to switch gears now if we're going to mobilize the interest of the average citizen in society, but also of legal frameworks and policy frameworks, then we need to be moving into what can we do? What is the appropriate response? How do we invest to demonstrate that when we do invest in conservation action, that it leads to the outcomes that that we say will happen if we protect, conserve and restore biological diversity in all its forms? So I think there is an important opportunity for biodiversity scientists to switch the frame, not ignoring the negative, but pointing to the positive, pointing to the solutions.

00:26:25: Hahn: So we've covered a lot of topics in our conversation. My last question to you is, could you please summarize in a nutshell how you see biodiversity change as something that the listeners can remember? Let's say in a week or two from now.

00:26:47: Gonzalez: First point, the biodiversity is changing globally. Terrestrial biodiversity, freshwater and marine biodiversity is going through an enormous reorganization and restructuring. It's happening at every scale in response to human impacts. We can see the signal of change at every scale. We have enormous uncertainty for any particular location or particular taxonomic groups. The rate and the magnitude of change over the coming decades. We need better models, better data, and a stronger consensus within the community. But this is highly scientific. There's a strong science basis, and that this knowledge we need moving forward to guide conservation action. So from my conclusion is that let's not oversimplify this discussion. We have to recognize that nature is complex, and that inherent beauty that we see and recognize in nature is changing in ways that are and will be unrecognizable in decades to come, as species are restructuring re shifting their distributions and the composition of communities is changing. So for me, it's about setting that change, understanding what we can do in any given context to respond to those those human impacts that we recognize.

00:28:23: Hahn: Thank you very much for this conversation, Andy. 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.