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A paper, published in Nature Ecology and Evolution, reports that biodiversity in the UK may be increasing slightly.
Dr Ester Gaya, Senior Research Leader for Comparative Fungal Biology, Royal Botanic Gardens, Kew, said:
“This is a well-crafted thorough study which presents interesting results. Regarding lichenised fungi, our specialty at Kew, we are not surprised species occurrence has increased substantially over the study period due to reduction in SO2 levels. The fact that two unrelated groups of organisms such as lichens and bryophytes are lumped together may be masking some the authors analyses. This study raises a flag, what are the new pollution sources that are affecting these communities.”
Prof Dave Goulson, Professor of Biology (Evolution, Behaviour and Environment), University of Sussex, said:
“This paper attempts to infer how populations of various wildlife groups are faring in the UK by use of ad-hoc records to estimate range changes of species using a complex modelling approach. On average the majority of species seem to be increasing. This seems to be at odds with direct monitoring of actual populations, as for example in the UK butterfly and moth recording schemes. The bee data seem to even disagree with the same research group’s publication from 20191. The authors don’t comment on this or show their patterns for butterflies.
“While it would be great if these increases were real, I have doubts which are best explained by an anecdote. About ten years ago Dr Bob Dawson was great yellow bumblebee project officer for the Bumblebee Conservation Trust. This is a rare bee found at a few locations in NW Scotland. Bob’s hobby, when not encouraging measures to conserve this bee, was to deliberately visit ten kilometre grid squares close to the known populations but from which the bee had not recently been recorded, and to hunt for it. By doing so, he approximately doubled the known UK range of the species. Anyone looking just at the records on a maps would think that the great yellow bumblebee underwent a remarkable range expansion in about 2010. In fact, the bee probably didn’t go anywhere – but Bob did.
“Recorder effort has greatly increased in recent years, along with the publication of new ID books, online guides, recording Apps and so on. There are more Bobs than there used to be. Obviously, the more people look, and the more experienced the recorder, the more they will find. No matter how clever the modelling, it cannot fully take into account changes in recorder experience, effort and behaviour.
“It is unfortunate that the Nature press release associated with this paper does not acknowledge or attempt to explain why this study suggests positive trends in insect life when so many other studies have found negative trends. The data on bees appear to be at odds with a similar study published only last year by the same group, while the moth data contradict the UK’s moth trapping scheme which directly measures moth populations.
“It also does not explain that the calculations are based on the outputs of complex models that attempt to construct estimates of changing species’ ranges over time from very sporadic and patchy records that are susceptible to changes in recorder number, interest and knowledge. Wildlife recording has seen a huge surge in popularity in recent years, aided by recording apps and bioblitzes, which could make species appear to increase in range.”
Dr Keith Kirby, Woodland Ecologist, University of Oxford, said:
“This paper highlights that changes in species richness depends on the groups of species considered, but also the nature of the measure involved. Occupancy (the number of squares occupied by a species) is a valuable measure, but it has a complex relationship to species abundance (the number of individuals in each square) – the same occupancy level occurs whether it is one or 5,000 individuals in a 1 km square. Occupancy is thus a useful measure but must not be the sole measure of species occurrence and abundance.
“There is a risk (which applies also to papers that have reported major species declines) in grouping large numbers of species together – inevitably some will be increasing even if most are declining because they have different requirements. The declines of one species cancel out the increases in others. This is particularly a problem with invertebrates where it is unlikely that any single pressure or opportunity is likely to affect all species in a similar way.
“It is probably significant that the two groups with the clearest patterns – lichens and freshwater species – are those where poor air/water quality was a major factor in past declines and has now been improved.
“There has also been improvements in recording since the 1970s particularly in some of the previously underworked groups such as lichens. In some cases, there have been campaigns targeted at rare species to check whether they still occur in places where they have been previously recorded.”
Prof Jane Hill, Professor of Ecology, University of York, said:
Does the press release accurately reflect the science?
“Yes, the authors analyse a vast quantity of citizen science records, to reveal different patterns of change since 1970.
Is this good quality research? Are the conclusions backed up by solid data?
“Analyses are based on 24 million species records from more than 5000 species, so it’s an amazing data set. The UK is probably the only place in the world where such analyses are possible because of our long history of recording nature, since Victorian times. But even so, the analyses only go back to 1970, and we know there will have been many changes to UK landscapes before this time, although it coincides with the start of warming from human-induced climate change and intensification of UK agriculture in the second half of the 20th century.
How does this work fit with the existing evidence? What does the report tell us about insect biodiversity? Does this fit with our studies specifically on insects?
“Other recent studies reporting ‘insectagedon’ implied more or less universal rapid loss of insect biodiversity, but it’s been clear for many years that the story is far more complex, with winners and losers in the Anthropocene. This study reveals this complexity, showing different outcomes among groups and over time.
Have the authors accounted for confounders? Are there important limitations to be aware of?
“The authors analyse occurrence records which are collected ad hoc without constant-effort sampling, making analyses of change challenging – hence the authors’ use of occupancy modelling to try to take account of recorder effort. However, the best data sets for quantifying biodiversity changes are from constant-effort monitoring of the same sites over many years. But these types of data are limited to just a few taxa from relatively few sites. Hence why the authors instead analyse occurrence records. But relationships between occupancy trends and abundance trends are unclear, for example a species could increase its range overtime, at the same time as declining at sites within its range.
What are the implications in the real world? Is there any overspeculation? As this analysis only looked at invertebrates, non-vascular plants and lichens, can we conclude biodiversity in general is recovering?
“The paper shows that patterns of increase and decline are complex, varying among taxa, among species and over time. Evidence that improvements to water and air quality have impacts for groups most sensitive to these factors provides the good news that we can reverse declines by improvements to the environment.”
Dr Christopher Ellis, Head of Cryptogamic Plants and Fungi Section, Royal Botanic Garden Edinburgh, said:
“The paper reports an increase in the number of grid cells occupied in the UK for approximately 5000 species (occupancy), since 1970. To do this, occupancy is averaged for species grouped as insect and non-insect invertebrates, bryophytes and lichens, as well as separating these as freshwater or terrestrial.
“The paper is important, because it demonstrates the value of recording schemes – the army of naturalists (often ‘amateurs’) who roam the British landscape finding and recording species – and because of this effort, and recent statistical advances – the authors were able to harness approximately 24 million individual records for their analysis.
“The paper strongly indicates that environmental regulation leading to cleaner waterways and cleaner air are having positive effects, with average occupancy increasing for freshwater species, and air pollution sensitive lichens, for example. Thus, average occupancy is increasing across all the species groups tested but the authors warn that these increases are measured since the 1970s, and we know that there were major losses of these species groups during the Industrial Period – the extent to which recent increases since 1970 recover past, historic losses, remains an open question.
“The paper reports occupancy trends averaged for the species groups, but there are individual species within these groups that decline although the overall message is positive. This is important because it shows that we can reverse past declines in biodiversity, however there are still threats to species that remain to be addressed.”
Prof Eric Allan, Head of the Community Ecology Group, University of Bern, said:
“This study puts together an impressive dataset including several different organisms, to look at changes in how widespread 1000s of species are across Britain (occupancy). The study is novel as it looks at typically understudied groups: insects, other invertebrates, mosses, lichens and aquatic species. This is very valuable as we have little information on how many of these groups are changing over time. It is important to note that the authors do not claim to represent total biodiversity and it is well known that other groups such as flowering plants, butterflies and birds are declining strongly with intensification of farmland management.
“Overall, the results emphasise that changes in biodiversity are complex. We know that many groups and species are declining around the world but there are also some more hopeful messages, such as the recovery of aquatic animals in Britain, highlighted in this study. The results are certainly no excuse for complacency: human actions are having very severe impacts on the natural world and the loss of biodiversity threatens our societies. However, improved knowledge on how different types of organism are responding will allow us to better target management and to work out if conservation measures are effective.
“Methodologically, the authors analyse data on species recorded in 1km2 areas across Britain: these data are hard to analyse because they only contain information on when a species was seen, not information on species absences. However, the authors use some advanced statistical approaches to correct for this. The study also looks at changes in the number of 1km2 areas occupied by species, not at changes in their abundance (number of individuals). Although the authors argue these are usually correlated, this is not always the case and data on changes in abundance would be very valuable. However, long time series on abundance of invertebrates or mosses do not exist across several sites and this analysis is therefore valuable in shedding light on changes in these poorly known groups.
“To conclude, more long-term monitoring of biodiversity and analyses like this one, that apply advanced analysis to existing data, are essential.”
Dr Nathalie Pettorelli, Senior Research Fellow, Zoological Society of London (ZSL), said:
“Wildlife in the UK is among the most intensively monitored wildlife in the world, with e.g. the number of species occurrence records for the country being among the highest in the world. Access to such unique data enables scientists to explore how different facets of biological diversity are responding to large scale changes in environmental conditions and compare trajectories across these different dimensions – something that is critical for developing a comprehensive understanding of how biodiversity responds to global environmental changes.
“What’s interesting with this study is that it focuses on changes in the proportion of the country where invertebrates, bryophytes and lichens species can be found – as opposed to changes in species abundance, to conclude that many invertebrate and plant species are now found in more parts of the UK than 45 years before. To some extent, these results may be linked to the impacts of climate change on invertebrate species in the UK, with numerous species having been reported to be on the move and heading north as climate warms. Interestingly, the results reported in this study contrast with previous reports which for example highlight how insect abundance has plummeted in recent years, illustrating how important it is to develop a comprehensive understanding of the mechanisms shaping changes in biodiversity patterns to effectively support biodiversity recovery.”
Prof Andy Purvis, Research Leader, Natural History Museum, said:
“This study is absolutely excellent and really raises the bar. Most biodiversity indicators are heavily biased towards vertebrates, but insects are the real engine-room of ecosystems so it’s crucial that we understand how insect populations have been changing. Although the UK has better data than anywhere else, they’re still challenging to analyse well, and this is the first synthesis that has risen to that challenge. They’ve analysed over 5000 species with an average of nearly 5000 occurrence records each, and their analysis handles the fact that species aren’t always recorded even where they’re present.
“This analysis gives a wonderful picture of how insect, freshwater, other invertebrate, lichen and moss populations have changed in the UK since 1970. But the UK has a long history of intensive pressures on biodiversity – the Industrial Revolution started two centuries earlier. So, the authors are right to warn that we shouldn’t view the levels in 1970 as a target: many species will have declined hugely in the previous 200 years. Also, we have to bear in mind the broader context here. The upturn in the fortunes of UK biodiversity is linked to better environmental protection; but another consequence of stronger environmental protection is that we have increasingly exported environmental damage to countries in the developing world – where biodiversity is richer, people are poorer and environmental protections weaker. So, when considering the state of nature in the UK, policymakers need to take a holistic view – what is our net impact on biodiversity globally, not just in the UK? Otherwise, the danger is we’ll keep trashing the unique, amazing and wonderful biodiversity in places like tropical forests, because we can’t see the damage that we’re doing.
“Although this study didn’t look at every taxonomic group – no vertebrates for instance – it looked at a much more representative set of species than most biodiversity indicators do. That’s a real strength of this paper.
“‘Insectageddon’ has been in the news in the last couple of years. This paper tells us that, in the UK, the picture over the last 45 years has been an increase rather than a decline, but with lots of churn – 10% have species have tripled in range whereas another 10% have lost over 60% of their range. This doesn’t conflict at all with suggestions that insects are declining globally (because the pressures on nature are increasing across much of the world), nor with some amazing case studies that have demonstrated alarming local declines (because this study is at a different spatial scale). Rather, it shows that overall declines aren’t inevitable, if there are strong environmental protections. That gives us all grounds for hope.”
‘Complex long-term biodiversity change among invertebrates, bryophytes and lichens’ by Outhwaite et al. was published in Nature Ecology & Evolution at 16:00 UK time on Monday 17 February.
DOI: 10.1038/s41559-020-1111-z
Declared interests
Prof Dave Goulson: “No conflicts to declare.”
Dr Keith Kirby: “No conflicts”
Dr Christopher Ellis: “No conflicts”
Prof Jane Hill: “I collaborate and publish with staff based at UKCEH and at the RSPB, but not these specific authors. My research has used these occupancy data sets to quantify the rates at which species are shifting their ranges northwards in the UK as a consequence of climate warming.”
Prof Eric Allan: “I don’t have any conflicts of interest around this study or field.”
Dr Nathalie Pettorelli: “No conflicts”
Prof Andy Purvis: “No conflicts.”