What Does the New Living Planet Index Tell Us?

: McRae: The other misconception is that that decline is seen everywhere in all regions, for all species or all populations, and that's not the case. It's just a global average. So if you want to know more, you've got to dig into the to the details. And actually about 50% of the populations in the index show stable or increasing trends.

00:00:26: 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 impact unit at iDiv. In this episode I will discuss the Living Planet Index with Louise McRae. Louise is a researcher at the Zoological Society of London. For several years, she has played a leading role in developing the Living Planet Index or LPI. The LPI is a measure of the changing state of global biodiversity and it is updated every two years. The latest update was published today, October 8th, 2026. The LPI has received a lot of media attention in the past, but some media coverage has misrepresented what the index actually shows. So what does the LP tell us and why is it so often misunderstood? Enjoy this episode of Inside Biodiversity. Before we talk about the Living Planet Index. Can you briefly tell me why did you become an ecologist in the first place? And what did you get involved with the LPI?

00:01:31: McRae: I've always been interested in the natural world. I think that was sparked from quite a young age. Both. Both from watching nature documentaries, but also spending summer holidays in the wilds of Scotland, kind of really kind of got that, that passion started. And then, yeah, I studied at my undergraduate and then following on from that, my master's ecology related subjects and, um, and yeah, I got involved with the LPI and there was a voluntary position advertised at ZSL. Um, it was soon after the, um, the LPI became a joint collaborative project between the ZSL, the Zoological Society of London and WWF. Um, and it was a voluntary position to come and help with the data and, and the database and sounded interesting. So I went for it and joined the project. Soon after that, I managed to get some funding to get a research position and and. Yeah.

00:02:41: Hahn: So how long have you have you been dealing with the LPI?

00:02:45: McRae: Well, I suppose it's been 20 years now. Um, so quite, quite some time, but yes, yes, I, I stayed and never left.

00:02:56: Hahn: So the new Living Planet Report and Living Planet Index have just been released. And the LPI shows a 73% decline since 1970. What exactly has declined by 73%?

00:03:14: McRae: So it's, uh, it's the index that has declined by that percentage. I try and make that clear when communicating these results, so that it's clear that we're referring to how the index has changed, rather than how a set of populations has changed, or trying to avoid the misconception that this might apply to all of biodiversity or all of species, for example. So it's yeah, it's actually the index that has changed by 73% and that is arrived at through a calculation of a weighted average of population trends. And there are thousands of vertebrate populations within the index itself, but this is the result of a weighted average.

00:04:01: Hahn: So the LPI only only counts vertebrates, right? So. So fish, amphibians. Reptiles, birds and mammals.

00:04:09: McRae: Correct.

00:04:09: Hahn: Not insects. Not plants.

00:04:12: McRae: No. With. With the slight exception that recently, um, with some collaborators, they developed a an LP for butterflies. So one of the better monitored insect groups. So yeah. The it I think getting abundance time series on on many invertebrates and insects in particular can be quite challenging. So um, I think with, with the LP, we're trying to improve the dataset for vertebrates. Um, but then trying to see if we can apply it to different groups.

00:04:44: Hahn: Okay. But but the current version, the one the, the 73% decline that is vertebrates only.

00:04:50: McRae: Correct. Yeah. That's vertebrates only. It's population trends. And just for clarity, we've referred to population as a sort of a broad term of a species monitored at a particular location over time. So it's not always a population in the ecological sense of the word, although many are, but some are monitored at the national scale, for example.

00:05:13: Hahn: And how is the the LPI then calculated? You said that you do this weighting.

00:05:21: McRae: Yes. So before that I felt before I can explain the various steps to calculating it. First of all, the abundance time series are modelled within a generalised additive modelling framework.

00:05:35: Hahn: So just sorry. Sorry to interrupt. So abundance just for clarification means the number of individuals within a population right.

00:05:44: McRae: Yes it does or a proxy. So we don't have counts of individuals for every population time series. So it can refer to an absolute count. It can refer to a modelled estimate of population size. It can also be biomass or density or some other proxies. For example the number of nests, if that's representative of the population size and then often for fish will have catch per unit effort. So. So yeah, as long as the measure is intended to gauge the abundance of, of that population, then we can use that measure. The modelling framework uses either a generalised additive model to model the long term trend for time series, which have six or more data points. If there are fewer than that, then a log linear trend is used. So that's the first step. And then those model trends are aggregated. Um, and the first step is that each population carries equal weight within a species. So all population trends are aggregated to that species. If there's more than one population trend available, and then species are aggregated within these taxa and geographic realm subsets. So we divide the data set up by biogeographic realm. So Afrotropical, Nearctic, Palaearctic and so on. Uh and we also divide it up by broad taxonomic group. So we divide it into birds, mammals fish and herp owls. So we combine reptiles and amphibians into one group.

00:07:36: Hahn: And the reason for that is that you don't want to underestimate badly monitored species. Right. Or badly monitored areas in the world.

00:07:46: McRae: Correct. Yeah. It's about trying to Balance a data set that doesn't perfectly represent biodiversity patterns, sort of spatially or taxonomically. So yeah, it's trying to rebalance that. And this is where the the weighting comes in as well. So so we have we divide the data into these subsets. And then we apply a weighting which is proportional to how species rich that group is. So for example if we think of terrestrial populations, the biogeographic realm that gets the highest weight is the neotropics, because it has more vertebrate species than the other realms. And then within the Neotropics, um, I think if my memory serves me well, I think it's the, the herp tiles within the terrestrial component of the Neotropics and so on. So that that's how it is proportionally weighted. And and yeah, the reason being is because if we didn't do that and the index hasn't always followed that approach. So and we found that when we didn't have that weighting system, the data set was dominated by those well studied regions and taxa. So it was trends were often driven by bird and mammal trends from Europe and North America. So it was an attempt. It's not a perfect solution to that problem, but it's an attempt at trying to rebalance the data set and the trends.

00:09:21: Hahn: And since there are approximately twice as many bird species worldwide than mammal species, also, then birds count double compared to mammals within the LPI. Is that right?

00:09:35: McRae: Yes. Yes. Correct. And and if we think about the marine system. So the marine index is mostly fish. So I come in for as 90 something percent of vertebrate species. Vertebrate marine species are fish, so it essentially becomes a very fishy dex. Respect.

00:09:55: Hahn: You've explained what the LPI shows, how it's weighted, but you also mentioned that there have been misconceptions in the past. So what are the most important misconceptions? What does the LPI not show?

00:10:09: McRae: Yeah, that's an important one to to mention. So it does not show population or species losses. So I try and make sure when I'm communicating I use words like decrease or decline rather than loss. So that that avoids that that misinterpretation. I guess it doesn't represent all of biodiversity or all of vertebrate species. Again, I try and emphasise that we talk about monitored vertebrate population. So we know that the LPI is only representing those populations That we have data for. We can't. It's it may be indicative but we don't know that. So we can't extrapolate beyond the data set that we have.

00:10:57: Hahn: So I think that's about like ten, 10% of of known species are covered by the LPs at about. Correct.

00:11:04: McRae: I think that's about correct. Yes. Yeah. It varies among taxonomic groups.

00:11:08: Hahn: But yeah, which shows the large gaps of knowledge that we still have.

00:11:13: McRae: Exactly. And I suppose the other misconception is, is that that decline is seen everywhere in all regions, for all species or all populations. And that's not the case. It's just a global average. So if we want to know more, you've got to dig into the to the details. And actually about 50% of the populations in the index are show stable or increasing trends. And also if we look at trends across different regions. We see differences. So they're not showing. We're not seeing that trend everywhere. We're seeing positive trends in some species in some regions. So yeah, I think that's the other one that I think is often misconstrued. And and we're trying to emphasise the detail a bit more and trying to sort of show that that's not always the case.

00:12:08: Hahn: Um, I think that's also surprising when you hear that half of the populations are declining, but then the overall index is a -73%. Why is that? I mean, how does that come about mathematically that the numbers is so low, even though that, as you said, half of the populations are stable or even increasing?

00:12:35: McRae: I guess there's two, two main explanations to that. And one is that the magnitude of the declines outweigh the magnitude of the positive trends is one but the other. It comes down to the, um, the weighting system. So we find that some of the populations with some of the largest declines occur in some of those high weighted regions and taxonomic groups. That's another reason why that then causes an overall decline in the index. Um, can.

00:13:16: Hahn: You give an example? Can you give an example of, of, uh, of a population or an area where the declines are high and that gets this, this high weighting?

00:13:26: McRae: Yeah. So for example, uh, we divided up the, the population trends into different trend categories from strong increase, moderate increase to moderate decrease in strong strong. Excuse me. Strong decrease. um, for example, and within the terrestrial component, we find that over half of reptiles and amphibians in the Neotropics are showing a strong or moderately moderate decrease in. Actually, 57.2% of those populations showed a strong decrease. So that's just one example of how that can lead to that overall stronger decline in the index.

00:14:13: Hahn: Since we've mentioned the Neotropics a couple of times. So that's mostly Latin America. Is that right?

00:14:21: McRae: Yeah. The Neotropics is um, yeah. Everywhere south from I think the it includes Mexico and the southern, very southern part of the US.

00:14:32: Hahn: What would you say are the most concerning trends that you found within those, uh, many, many trends that you aggregated in the LPI. And are there also some more positive or encouraging trends? You mentioned that there are quite a few populations that are also increasing. Maybe you can give us a few examples of ups and downs.

00:14:56: McRae: Yeah. Yeah, sure. I think in terms of the most concerning, we see the largest decline in the Latin America and Caribbean index. Um, and this decline we see on average amongst each of the taxa, um, not not to the same extent. It seems to be, uh, more severe in the fish populations and the herb populations than the birds and mammals. Uh, and we so alongside the population data in the LPI. We also collate information on local threats where that's available. And so we try and summarise the these threat information for each of these regions and for the Latin American and Caribbean one we find the habitat degradation. Fragmentation is the major threat to those populations. But we also see within the freshwater realm as well that things like infrastructure, for example, dams are blocking migration routes for fish, but also overall, excuse me, overexploitation is another local driver of change there. And this sort of also connects with, I guess, another of the indices that tend to show more concerning trends, which is the freshwater LPI. So freshwater species in general I think we have two issues. One is that they are the least well-represented of species within the index, um, and the often the smallest data set, but also it's where we see some of the larger declines as well. And that's amongst amphibian species, but also freshwater fish for some of the reasons I just mentioned for that, that those blockages to the migration routes for a lot of migratory fish. On the more positive side, um, so from the regional trends, North America and Europe and Central Asia, out of the regional trends do still show overall declines, but they're not at all to the magnitude as the other regions. But it's important to note that the baseline of 1970 is a sort of an arbitrary one. And it doesn't mean to say that each of these regions had the same sort of state of biodiversity as each other at that time, because we know that in Europe and North America, a lot of the impacts on nature did also occur prior to 1970. So I think it's difficult to compare. Make a direct comparison between those two. But having said that, there are examples of positive trends in those regions. And a few years ago, we looked at 50 species of birds and mammals that were recovering in Europe. And the reasons behind that. And so we looked at, for example, the European bison, which has recovered in Europe from being extinct in the wild in the 1950s and recoveries in other in in carnivore species as well, across Europe and in many bird species. So here in the UK we've seen, for example, the white tailed eagle make a comeback in the red kite. And a lot of these. It's a combination of a lot of conservation efforts like quite targeted conservation efforts, but also some policy changes and legal enforcements. But yeah it's important to keep an eye on what's working and what, you know on these positive trends amidst the kind of global picture.

00:18:47: Hahn: What about current trends? It's important that you mentioned that the LPI covers the time from 1970 until today, or I think two years ago. That's when the when the data series ends. And how has it changed over that time? So is it at the moment further declining in a linear way, or are losses or declines decelerating or accelerating? Can you see that in the data?

00:19:19: McRae: We can't see a change yet in the data. So generally when we look at the average annual rates across each year, they do vary. But we don't see a big change over time. When we look at decadal rates again, there's some differences from decade to get to decade, but those differences are quite small. We did see in the last two years. So the index runs to 2022. So between 2020 and 2022, that average, um, the average of the annual rates there was slightly lower than previous decades. But I think because it's only based on two years, that might be a bit too early to say. If that's a positive sign. I mean, hopefully it is. But yeah, I think we wouldn't want to make that assumption based on just two years.

00:20:16: Hahn: Can we see where it's going? Can we make any guesses where the index will be in 30 years from now?

00:20:22: McRae: Yeah, that's a good question and a tough one. Some research has been done to project the LPI into the future based on scenario models. That's obviously as only as robust as those scenarios are. Um, and it shows how the LPI might perform under different changes in land use and climate change, for example. I guess the business as usual scenario shows a continue trends approximately about the same rate as we currently see, so I don't think that's a huge surprise that that, you know, that's what we find. But um, but we certainly see that both with increases in protected area in conservation and changes to, to land use policy, that that would have an effect on the LPI if those changes were implemented. And then we would see that change in trajectory.

00:21:19: Hahn: So we haven't bent the curve, but there are options of doing that in the future.

00:21:24: McRae: Yeah, exactly. And I think it's important to try and explore that with the with these biodiversity indicators to try and look at those different possible futures and what how the index might behave under those different scenarios.

00:21:39: Hahn: I skipped one question that I really want to come back to, because I think it's important, and maybe it wasn't clear yet when you calculate the LPI. If you have a large population of a certain species, the change of that population in terms of percentage counts as much as the percentage change of a small population, which to me was a bit surprising when seeing that, because I would assume that if a large population declines by, let's say, 30%, that would count more than a small population like fewer individuals. Why don't you account for the size of the population?

00:22:21: McRae: Yeah, that's a good question. Um, that was a decision originally taken when the LPI was developed in in 1998. It's still a current decision that we haven't changed yet, but I think it's one that's worth exploring. I suppose there's a sort of value based decision of each population, and each species being equally important and not wanting to to have the index dominated by very common species versus rare species. A while ago, we did explore this by weighting populations by the proportion of the global species estimate that it represents. So trying to put higher weight on those populations that represent more individuals. Um, so I think it's something.

00:23:12: Hahn: Of that same species. So that's within one species.

00:23:16: McRae: Exactly. Yeah. And I think that would be interesting. And I and I think sort of from a functional perspective, it certainly it could make sense from, from that side of things. It's the current decision of how the index is calculated, but I think it doesn't mean to say that it can't be looked in those different ways and explored, particularly if the interest is looking more the ecosystem or the functional perspective.

00:23:44: Hahn: How useful is an index that's only one number representing how biodiversity is faring globally? And how useful is it in particular when we want to take action on conserving restoring ecosystems? I would like to read a critique that I saw from our World in Data, where they analyse the LPI and they wrote, quote. Unfortunately, averages are not particularly helpful in understanding what and where these populations are. When we look at more detailed analyses of the LPI, we find that actually this 73% average decline hides even more drastic declines in some populations. If we want to protect our most endangered species. These are the ones we need to prioritise, unquote. What do you respond to such a criticism?

00:24:39: McRae: I suppose I would agree with that statement. Um, because yeah, I think that's right. I do think that, uh, the overall index value, you know, hides some really interesting detail. And as an ecologist, that detail is really interesting. So I suppose I, I suppose I would respond. I don't think it's an either at all. I think having the single number has some value. Uh, but also digging into the detail is, is what you need to address particular management questions and finding out. Okay. Well where are we seeing declines, which taxa are most affected and why. Um, so just going back to the initial question, I think the single number. Well, it's what policymakers frequently ask for. So I guess that's the primary motivation behind producing an indicator that just shows what the global trend is. And I think there is value in just saying, look, this is what's happening globally on average. I think that is a sort of a starting point for a more detailed conversation. And likewise for like, I know a lot of people use the index as a scene setter. So if they're interested, you know, if they're writing a paper on freshwater species, they might say, well, look, the freshwater index is the most negative out of the three systems. This this is an alarm bell. We can see that freshwater species are likely to be under more threat. So. So yeah. So I think it can have a value on that side of things. But I certainly don't think it should be the only thing that the LPI is used for at all? Um, and I think that a lot of the work which goes beyond just using the index, actually uses the data in different ways. Yeah. We've got a huge, valuable database of all these population trends that we can do different types of modelling in to really get up those interesting questions. So I feel that, yeah, that there's I feel like the two things could be equally valuable.

00:26:57: Hahn: Yeah. At this point, I would like to also encourage our listeners to have a closer look into the technical report, because there you dig much deeper into the details that go way beyond this, this one index number. And you, you highlight some of, of the trends that you see in different biogeographic realms, in different species groups. So that's worthwhile having a look at. And I think you in the technical report, you, you also do a good job in highlighting some of the details behind that number. On the other hand, the LPI has in the past been sometimes misunderstood, and you mentioned that yourself. There has also been misreporting in the media about the LPI, where they misinterpreted what the 73% decline actually means. Knowing that has happened in the past, is there any way of of correcting for that? I mentioned the technical report, which has all of the details and explains well how the LPI is calculated, but I guess most journalists will not have a closer look at the at the technical report. So how do you make sure that the LPI is understood correctly? Not misinterpreted. Not misreported?

00:28:17: McRae: Yeah we try. Yeah. Firstly I recognise that that it's happened and it's yeah it's frustrating when your work is not communicated or not understood. And but I do acknowledge that it's, you know, it's my role as a scientist to try and ensure I'm communicating things both in a clear way, but also in a robust and accurate way for every report. Um, the so the LPI team who are based at, at ZSL, we write the, you know, the results in in a clear way and we emphasise phrases that are accurate, that can be used to describe the LPI and ones that are incorrect. So we try and make that very clear. We also review any press release. So we work closely with WWF on the press releases. And again check the language. Try and avoid words such as loss rather than decline so that we can avoid those sorts of misinterpretations. And also we're happy to try and share results. So for example, with our words in data, we've shared our results early with them so they can update their pages. And they have a really good comprehensive summary of of the misconceptions as well. And yeah, with the technical reports, whilst I totally agree, most journalists won't read it. We did try and write suddenly the initial section with journalists in mind, and it is circulated alongside the reports each time so that journalists could look at that as well. And the final thing in the any media briefing, either the WWF do or that I'm involved in, we will ensure that as part of the description of the new results, we do mention what this index shows and what it doesn't show. So yeah, so we've we've tried to You make as much as we can over the years to try and avoid any of these misunderstandings. Um, but yes, there's a certain point at which it goes out of our control, which is really unfortunate, but we certainly try our best.

00:30:37: Hahn: Uh, I know what you're talking about. I work as a press officer, and sometimes a press release goes out, and then it's not always correctly understood, or it's interpreted in different directions depending on on the journalist. Louise, let's wrap up this conversation. And, um, what would you like the audience to remember from this conversation? What's the most important point to you?

00:31:03: McRae: I guess one of the most important that I feel is that there's there is more to the LPI than than just the index and the and the single number that there's a huge database that underpins it with lots of valuable information and a lot of the research not just done by myself and my colleagues, but by many other people, have used these database to answer really interesting research questions. So I think if someone is interested in knowing more than just what the index is saying, then have a look at some of the papers that that have been published. And if you want to get a bit more involved in that, but also like to extend an invitation to collaborate as well. I think we're we're only a very few number of people who work on, on this index. And we can't we can't work on everything that we'd really like to. So I think if people have an interest in working on it, then please reach out.

00:32:09: Hahn: Thank you very much. That was a highly interesting conversation. If you enjoyed this episode, be sure to subscribe! Insight biodiversity is available on all major podcast streaming platforms.