Locations of Living Planet Index species populations
Map showing the locations of the monitored populations in the LPI. Newly added populations since the last report are highlighted in green and species new to the LPI are shown in red.
Source: WWF/ZSL (2020)
The data used in constructing the LPI are time-series of either population size, density (population size per unit area), abundance (number of individuals per sample) or a proxy of abundance (for example, the number of nests recorded may be used instead of a direct population count). The table below gives you an idea of what can and can’t be used.
If you have data you would like to contribute to the Living Planet Database, please get in touch with us at LivingPlanetIndex (at) ioz.ac.uk.
The headline trend from this Living Planet Report is that globally, monitored populations of birds, mammals, fish, reptiles and amphibians have declined in abundance by 68% on average between 1970 and 2016. But what does this actually mean? Below is a table of what the LPI is and what the common misconceptions are.
|Features of the LPI||Common misconceptions|
|The LPI is shows the average rate of change in animal population sizes||The LPI doesn't show numbers of species lost or extinctions, although some populations do decline to local extinction|
|Species and populations in the LPI show increasing, declining and stable trends||Not all species and populations in the LPI are in decline|
|About half of the species we have in the LPI show an average decline in population trend||The LPI statistic does not mean that 68 per cent of species or populations are declining|
|The average change in population size in the LPI is a decline of 68 per cent||The LPI statistic does not mean that 68% populations or individual animals have been lost|
|The LPI represents the monitored populations included in the index||The LPI doesn't necessarily represent trends in other populations, species or biodiversity as a whole|
|The LPI includes data for threatened and non-threatened species - if it's monitored consistently over time, it goes in!||The species in the LPI are not selected based on whether they are under threat, but as to whether there is robust population trend data available|
LPI results are calculations of average trends. This means that for the global LPI some populations and species are faring worse than a 68% decline whereas others are not declining as much or are increasing. The average trend calculated for each species in the LPI shows that just over half of reptile, bird and mammal species are stable or increasing. Conversely, the average trend for over 50% of fishes and amphibians species shows a decline.
As the number of species which have positive and negative trends are more or less equal, this means that the magnitude of the declining trends exceeds that of the increasing trends in order to result in an average decline for the global LPI. This also suggests that the global LPI is not being driven by just a few very threatened species, but that there are a large number of species in each group (almost 50%) that together produce an average declining trend.
If we look at trends at the population level, a similar pattern emerges, although in this case amphibians are the only taxonomic group with over 50% of populations showing a negative trend.
The LPI database contains data gathered from different sources and collected at different scales, and not explicitly for the purpose of the analyses presented in the Living Planet Report. It therefore consists of time series of varying lengths (interval between the first and the last observation) and fullness (number of observations over the total number of years). For some species/groups, however, only shorter time-series are available, as shown in the figure below. Whilst time series for birds and mammals are longer, amphibians are almost exclusively represented in the database by shorter time-series. Long-term data are often available for species/groups that are doing better on the whole. We gather all available data in order to detect trends that might be important from a conservation perspective.
To gauge whether the inclusion of these shorter time-series might be skewing the results of the global LPI, we re-calculated the trend excluding short time-series (Figure 8). Overall, the removal of shorter time-series appears to have little influence on the overall trend, with the trend calculated excluding time-series with less than 3 years of data largely overlapping with the global trend. Trends calculated excluding time-series with less than 5 and 10 years of data diverge from the global trend from 2002 and 2003, respectively. However, the confidence intervals around these trends overlap for the most part with the confidence intervals around the global trend, and the final index values differ from the final value of the global trend by 3 and 5% respectively.
In September WWF published the 2020 Living Planet Report – a report that tracks the status and trends of wildlife populations across the globe, using ZSL’s Living Planet Index.
Tracking the status and trends of wildlife is critical both for understanding the health of the ecosystems on which we rely, but also to identify those animals and places that are most in need of conservation action.
In the 2020 report, data was drawn from 20,811 populations of 4,392 species, and revealed an average 68% decline (-73% to -62%) in monitored populations between 1970 and 2016: a statistic that threw a spotlight on biodiversity loss and can be used to spur conservation action in the areas where it is needed the most.
To calculate the Living Planet Index itself, we combine population trend data into a global index using time-series modelling and a weighted average, giving us a single trend of average changes in abundance since 1970 (Collen et al, 2009; McRae et al, 2018). But we know that biodiversity trends can differ in different places - in the latest Living Planet Report, we identified differences in average population trends in different IPBES regions (the geographic regions defined by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services).
We also know that the pattern of the global trend is not the same for all species in all regions (Figure 1 & Table 1). For example, populations in temperate regions such as Europe-Central Asia and North America have, on average, declined less severely than those in tropical regions. One reason for this may be that the impacts on wildlife in these northern regions might have occurred prior to the baseline year of the Living Planet Index, which is 1970.
Figure 1 - Living Planet Index trends for IPBES regions. The white line shows the index values and the shaded areas represent the statistical uncertainty surrounding the trend (95%). All indices are weighted by species richness, giving species-rich taxonomic groups in terrestrial and freshwater systems more weight than groups with fewer species. Source: WWF/ZSL (2020)
Table 2 - Changes in the number of populations and species for different taxonomic groups between LPR 2018 and 2020. WWF/ZSL (2020)
Research into biodiversity loss and its trends never stops: in a new report published today in Nature (Leung et al. Nature 2020), we highlight that the underlying statistic of the LPI can be sensitive to both extreme population increases and declines – this isn’t a new revelation (see Gregory, et al. 2019; Buckland et al., 2011), but it is an interesting one to explore.
In this latest data analysis we explored removing the most declining populations (resulting in a shift of the average trend to stable) in addition to removing the most increasing populations, and removing both sets of populations together. Figure 2 replicates this analysis using our most up-to-date dataset of 20,000 populations (from LPR 2020). This includes removing the most declining populations (Figure 2a), removing the most increasing populations (Figure 2b) and also removing both (Figure 2c). Importantly, removing 10% from both extremes (20% of the populations) still reveals a decline of 42% since 1970.
Figure 2 - The global Living Planet Index after removing proportion of the most declining (a), increasing (b) and both (c) subsets of the dataset. Top row shows just the mean trend, bottom row shows the trend with 95% bootstrapped confidence intervals.
We then used a new method to identify and highlight clusters of extreme declines. We found extreme declines occurring in 16 species-group/regions - in particular species-groups like Indo-Pacific birds, or tropical reptiles. These clusters represent just a small number of populations (about 1%) from the overall total. Removing these clusters leaves a distribution of populations that appear, on average, to be stable.
However, this doesn’t mean that the remaining 99% of all populations in the LPI are doing fine. While there is no overall average trend across these species, this masks important underlying variation. In particular, three groups across the Indo-Pacific show widespread declines and there is some suggestion that smaller species may be more impacted than larger species.
It is also important to note that the LPI analysis focuses on population declines - our dataset includes many populations of the same species. While the new analysis published in Nature would consider populations of the same species separately, the LPI would average them together for an overall species trend.
Figure 3 - The proportion of species (top) and populations (bottom) in each taxonomic group where the average trend is an increase (blue), is stable (green) or a decline (red). WWF/ZSL (2020)
In the global LPI we see an average population decline of 68%. This represents an overall average, with some populations declining more and others that have not declined as much, or are even increasing. The average trend calculated for each species in the LPI shows that just over half of reptile, bird and mammal species are stable or increasing (Figure 3, top). Conversely, the average trend for over 50% of fish and amphibian species shows a decline. When we explore how LPI populations are changing we observe a similar picture; roughly 50% of them are increasing and 50% are declining (Figure 3, bottom). As the number of species which have positive and negative trends are more or less equal, this highlights that the magnitude of the declining trends must exceed that of the increasing trends resulting in an average decline for the global LPI. We also note that these declines are more likely in regions that have a larger number of species. This is why the Living Planet Index uses a weighting system, otherwise it would be heavily weighted towards well-monitored locations.
The important point is that biodiversity trends vary, and in important ways. Better understanding of where and why some species are in particular decline is critical. Identifying these animals or places is an important step in prioritising conservation effort.
However, composite indices like the Living Planet Index (or others like the Red List Index , or Biodiversity Intactness Index ) are still some of the best overall measurements we have for outlining the global state of nature. The global LPI trend is an important tool in communicating to policymakers and to the general public, to catalyse attention and encourage a broader conversation around biodiversity loss. Indicators like the Living Planet Index can serve as barometers of ecosystem health, in the same way that stock market indices can indicate overall trends while containing a variety of different underlying stock trends.
Our growing open-access Living Planet Database provides unique opportunities to explore the drivers of global wildlife population change. It can be examined in greater detail to explore how particular species and regions are changing, or how different drivers are influencing population trends.
One of our continuing challenges is to make sure we have robust data for as many taxonomic groups and regions as possible to enable us to paint an accurate picture of how population trends differ from the global average. While there are comprehensive monitoring programmes for some species (e.g. European and North American birds, commercial fish stocks), records of population trends for many species groups are sparse and scattered through the scientific and grey literature. This is an important factor to consider as this means we often have many more populations or species for regions that have, at least recently, seen less biodiversity loss. For example, European and American species have much better monitoring data that tropical species, where we see greater losses. Encouragingly, we have been able to tackle some of our data gaps. Since the previous edition of the report in 2018, we added over 4,000 new populations and nearly 400 new species (Figure 2), increasing representation of many species groups and regions (Table 1).
Figure 4 - Map showing the locations of the populations in the LPI monitored in specific locations. Newly added populations since the Living Planet Report 2018 are highlighted in orange, or in red for species new to the LPI (WWF, ZSL, 2020).
Table 2 - Changes in the number of populations and species for different taxonomic groups between LPR 2018 and 2020. WWF/ZSL (2020)
A number of questions often arise about the Living Planet Index and answers to many of these can be found in the technical supplements of the Living Planet Report
Combining all these regional and taxonomic differences into a single index clearly masks a lot of the underlying variation in population trends. Identifying those animals or places that are in particular decline is an important step in prioritising conservation effort. However, composite indices like the Living Planet Index (or others like the Red List Index , or Biodiversity Intactness Index are still some of the best overall measurements we have for outlining the global state of nature. Without digging in to the underlying data, a single index cannot tell you about which species or regions are doing well or are not doing well, but it can give you a useful snapshot. Indicators like the Living Planet Index can serve as barometers of ecosystem health, in the same way that stock market indices can indicate overall trends while containing a variety of different underlying stock trends.
Such an overall measure of change in a complex system can be critical to detecting and communicating changes in the underlying system. For example, for a variety of scenarios of biodiversity change, Santini et al (2017) assessed a variety of metrics to detect these changes. They highlighted that a metric based on geometric mean abundance (like the LPI) in addition to another measuring diversity (Sørensen similarity index) were usefully able to detect many of the changes they explored.
While this new methodology helps to identify those species populations that are most in decline, excluding or segregating these from the remaining populations is complex. Should we present separate indicators of species in extreme decline? It isn’t clear that such an ‘index of declining populations’ would be useful. Understanding why some species are in extreme decline and what drives such declines will be an important next step. What we are investigating is how increasing the representation of our dataset can mitigate some of the sensitivities of the methods we use to such extreme increases and decline
No, the Living Planet Index is a measure of population trends, not extinction of species. There are a small number of populations in the Living Planet index that have been monitored to extirpation (loss of the population locally), but in most cases the LPI aggregates trends in continuing wildlife populations around the globe.
This is also not the case. The Living Planet index considers changes in small and large populations of animals to be equivalent. The LPI uses time-series of either population size, density, abundance or a proxy of abundance, the overall trend calculated represents an average trend in population change and not an average of total numbers of individual animals or species lost. Figure 5 explains this difference using three example populations of three different species, all of which declined but by different percentages. The tables show that although the average percentage change of the trend represented is 50%, the total number of animals in the three combined populations has not declined by this much, so we haven’t lost 50% of animals.
Figure 5 - An illustration of how the average percentage change of the trend differs from the change in total number of animals lost (in percentage). WWF/ZSL (2020)
Distilling many trends into a global mean index can of course mask variation. As mentioned above, not all populations in the LPI are declining rapidly, and some are increasing. This is why we also subset the data to show sub-indices for different regions and taxonomic groups. It’s important to show how the species within these subsets vary, and to capture the uncertainty of these trends. Several scientific studies have explored this research topic to try and uncover trends in vertebrate populations and how they vary according to location, species ecology and types of threats the species are affected by.
The global LPI trend is also an important tool in communicating to policymakers and to the general public, to catalyse attention and encourage a broader conversation around biodiversity loss. The LPI is one of the best tools we have for outlining the global situation, in the same way as changes in the FTSE All-Share Index give a sense of how the economy is faring (but tell us nothing about employment rates or fairness in salary distribution). Without digging into the detail, it also doesn’t tell us about which sectors are doing well or not doing well. Similarly, GDP tells us something about the state of the economy so it has a certain ‘overview’ value, despite its well- publicized shortcomings.
The Living Planet Index has not declined by 8% in two years. Each version of the index is essentially our latest snapshot or best guess of declines since 1970. We add many more populations and species to our dataset for each version (4,000 populations and 400 species in this case). Many of these populations include historical data from before 2016. As such, the entire index changes not just the last few years. It would be more correct to say that new data suggest that, since 1970, populations have decline by slightly more, on average, than we previously thought.