Tag Archives: Science

Flowers, feathers and time: a new study of the temporal dynamics of plant-hummingbird interactions just published

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What happens when you spend an entire year watching hummingbirds and the plants they visit in one of Brazil’s most unique ecosystems? You begin to unravel the complex, ever-changing relationships that tie together birds, flowers, and the environment they share.

In a new study jointly led by Steffani Queiroz and Marsal Amorim — and part of my ongoing collaboration with a brilliant team of Brazilian hummingbird researchers — we explored how plant–pollinator interactions shift over time in the Campo Rupestre, a montane tropical ecosystem rich in biodiversity and endemic species. Despite the region’s relatively stable climate, we found that the relationships between hummingbirds and flowers are anything but static.

Over the course of 624 hours of observation spread across a full year, we recorded over 9,000 hummingbird visits involving nine bird species and 47 plant species. Many of these plants — and one of the most frequent visitors, the stunning Hyacinth Visorbearer (Augastes scutatus) — are found nowhere else on Earth.

Our goal was to understand how the structure of this ecological network — which plants interact with which hummingbirds, and how often — changes over time, and what drives those changes. Are they shaped by morphological fit (the match between beak and flower shape)? By phenology (when plants bloom)? By nectar characteristics such as the amount produced and its sugar concentration?

What we discovered is that different factors dominate in different seasons. During the rainy season, when hummingbirds are more abundant, interactions were shaped mostly by morphological matching — suggesting that competition leads to greater niche partitioning. In contrast, during the dry season, the network became sparser and was more influenced by nectar sugar content and flowering patterns.

Interestingly, while the overall annual network wasn’t especially nested (a common pattern in mutualistic networks), it was highly modular — meaning that it contained distinct clusters of species that mostly interacted among themselves. This structure changed significantly across months, highlighting the dynamic nature of tropical plant-pollinator interactions, even in environments with relatively little climate variation.

This work highlights the importance of long-term, fine-scale studies in uncovering how interactions among species shift through time. It also underscores the remarkable biodiversity and ecological complexity of the Campo Rupestre — and the need to understand and protect it.

Here’s the reference – if anyone wants a copy, drop me a message via my Contact page:

Queiroz, S.N.P., Amorim, M.D., Lopes, S.A., Vizentin-Bugoni, J., Jorge, L.R., Ollerton, J., Santos, T. & Rech, A.R. (2025) Temporal dynamics of a Neotropical plant-hummingbird interaction network. Austral Ecology 50:e70089

And here’s the full abstract:

Species interaction networks are expected to vary following temporal changes in the environment and the composition of the local community. However, there are still gaps in our knowledge about temporal variation in networks in tropical areas, where less variable climates are expected to produce more stable community structures over time. Here we describe a plant-hummingbird network in the Brazilian Campo Rupestre ecosystem and investigate multiscale temporal variation of interactions in this community as well as the possible mechanisms underlying the frequencies of species interactions. Plants visited by hummingbirds were observed monthly for a year and each species had morphology, phenology and nectar traits measured. During 624 h of observation we recorded nine hummingbird species visiting 47 plant species, amounting to 9015 visits to flowers. Most plants (28 species) were endemic to the Campo Rupestre and mostly visited by the also endemic hummingbird Augastes scutatus (the Hyacinth Visorbearer). The annual network was not nested but presented high modularity and intermediate specialisation. While the overall (annual) frequencies of interaction were primarily defined by morphological matching and phenological overlap, we found a remarkable temporal change in community structure over the year, with different processes underlying interactions among plants and hummingbirds at different seasons. The interaction pattern during the rainy season was more similar to the annual network than the dry season (when nectar sugar content and plant phenology were also important), with more links per species and lower specialisation. The higher importance of morphology to predict interactions during the rainy season suggests higher niche partitioning when more hummingbird species are present in the community. Our results exemplify the importance of considering the temporal dynamics of the community to advance the understanding of the processes defining species interactions over time in the tropics.

My sincere thanks to Sinzinando Albuquerque-Lima for the photograph, which was taken in the Amazon, not where the research described above was conducted.

A new study examines why data quality matters in plant–pollinator databases

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Imagine trying to put together a giant puzzle where each piece represents an interaction between a flower and the insect, bird, bat or other animal that helps it reproduce. In recent years, scientists have gathered millions of these “puzzle pieces” into massive online databases, offering an unprecedented view of how plants and their pollinators connect around the world.

But there’s a catch: not every entry in these databases is equally reliable. Did the researcher actually watch the insect brush pollen against the flower’s stigma? Or did they simply note that the insect visited the blossom and assume pollination happened? Without clues about how each plant–pollinator link was documented, users can’t tell solid evidence from a best guess.

That’s why a growing number of projects are now tagging every interaction with a “data quality badge”—a short note explaining the exact kind of proof behind the record. For example:

  • Direct observation: A scientist observed an animal pollinating a specific flower.
  • Pollen analysis: Pollen grains matching that flower were found on the insect’s body.
  • Inferred pollinator: The animal regularly visits those flowers and shares similar traits with known pollinators.

Initiatives like the Pollinators of Apocynaceae Database and the Database of Pollinator Interactions (DoPI) have already adopted these quality flags. The upcoming USDA-NRCS PLANTS database is doing the same, and Brazil’s REBIPP network has developed a standardized set of terms—rooted in the global Darwin Core standard—to make sure everyone speaks the same “pollinator language.”

Why is this important? When you know the strength of the evidence behind each plant–pollinator link, you can:

  • Fill in real knowledge gaps with confidence.
  • Identify weak spots in our understanding that need more fieldwork.
  • Build better conservation plans, targeting the most critical pollinators for at-risk plants.

Ultimately, adding clear data-quality labels turns these massive collections of observations into powerful tools for science, restoration, and education. And that’s good news not only for researchers, but for every garden, farm, and wild ecosystem that depends on diverse and abundant pollinator communities.

These issues are explored in a new, open-access paper written by colleagues from Brazil, the USA and myself. In the paper we discuss the importance of data quality in plant-pollinator databases and suggest methodologies for improving it. Here’s the reference with a link to the paper:

Ollerton, J., Taliga, C., Salim, J.A., Poelen, J.H., & Drucker, D.P. (2025) Incorporating measures of data quality into plant-pollinator databases. Journal of Pollination Ecology 38: 151-160

This paper is a direct output from the EU-funded WorldFAIR Project in which I was involved, though we also acknowledge the SURPASS2 project as a precursor to this. Looking ahead, we’re also going to be adopting the recommendations from our paper in the new Butterfly Project (also EU-funded). Finally, by way of a teaser, I can tell you that our new paper will also be relevant to another large project in which I’m involved, that has successfully secured funding…but you’ll have to wait until later in the year to hear about that!

Thanks to Chris Taliga for the photo.

A new study shows how garden flowers keep city pollinators flying all year round

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When we think of cities, gardens might not be the first thing that comes to mind. But these green patches — whether in private yards, parks, or balconies — play a surprisingly important role in supporting urban wildlife. Among their most crucial guests? Pollinators like bees, butterflies, and even birds and bats.

In a new study just published, I teamed up with some Brazilian colleagues to explore how the different features of garden flowers help sustain pollinators throughout the year in a subtropical urban garden. While we’ve long known that garden flowers provide food for pollinators, what’s less clear is how specific floral traits — like shape, flowering time, and type of nectar or pollen — influence who visits which plants and when.

To get a clearer picture, we conducted weekly surveys of pollinators visiting garden flowers over the course of a year. We paid close attention to traits such as the depth of flower, the kind of resources offered (nectar vs. pollen), how closely related different plants were, and when they flowered.

What we found was striking: the network of interactions between flowers and pollinators was highly organized. Plants grouped into clusters, or “modules,” that tended to share similar physical traits and evolutionary histories — but interestingly, not the same flowering times. This meant that within each module, different plants flowered at different times of year, effectively staggering their blooms so that there was always something on offer for pollinators.

Even more intriguing was the discovery that most plants had just a few connections in the network, usually restricted to a single module. These “peripheral” plants accounted for over 85% of all pollinator visits. Meanwhile, a few special species acted as bridges between modules — their role in linking different parts of the network made them key to its stability. These connector species didn’t flower at the same time, which helped to maintain a steady supply of food for pollinators across seasons.

Not all interactions between plants and pollinators are “legitimate” in the sense of leading to pollination. Some animals visit flowers just for the food, without helping with reproduction. But our study found that these interactions still played a valuable role in supporting a diverse pollinator community.

So what does all this mean for urban gardeners and city planners?

First, it highlights how important it is to plant a variety of flowers that bloom at different times of year. Second, it shows that even seemingly minor plants or interactions can contribute to the ecological resilience of urban green spaces. And finally, it underscores that thoughtful planting — considering things like flower shape, blooming schedules, and diversity — can help keep pollinators thriving, even in the heart of the city.

Urban gardens aren’t just pretty — they’re powerful allies in the fight to support biodiversity.

The study was led by Brazilian research student Luis de Sousa Perugini. Here’s the reference with a link to the paper:

de Sousa Perugini, L.G., Jorge, L.R., Ollerton, J., Milaneze‑Gutierre, M.A. & Rech, A.R. (2025) High modularity of plant-pollinator interactions in an urban garden is driven by phenological continuity and flower morphology. Urban Ecosystems 28, 126

Here’s the abstract:

Garden flowers play a vital role in urban environments, supporting pollinator communities. Yet, the extent to which floral traits shape urban pollination networks remains poorly understood. This study investigated how garden plants shape year-round pollination networks, sampled in weekly surveys in an urban subtropical garden. We focused on the role of floral morphology (corolla depth), type of resource, relatedness, and phenology in the organization of interactions. We determined whether modularity and species roles were influenced by these floral traits, comparing if legitimate pollination, illegitimate (i.e. non-pollinating) interactions and all interactions had similar drivers. All networks were modular, and in the overall network plants within the same module were morphologically and phylogenetically similar while their phenology was significantly overdispersed throughout the year. Peripheral species, those with few interactions and restricted to a single module, dominated all networks, representing over 85% of interactions. We found that phenology was related to the species role of overall network connectors (species that connect modules) and legitimate module hubs (species that connect their own modules). Both showed no overlap in their flowering periods, providing floral resources at different times of the year. Each module functioned as a distinct unit, showing year-round availability of resources to support its pollinators. This suggests that resource continuity and trait-based filtering may shape pollinator assemblages influencing ecological resilience in urban habitats. Even interactions that do not contribute to plant reproduction can sustain a diverse fauna, highlighting the importance of these interactions in urban green space planning and management.

Have we passed “peak honey bee” in Britain? An update of hive numbers for World Bee Day 2025

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Since publishing what I believe are the most comprehensive data on the number of honey bee hives in Britain in my book Pollinators & Pollination: Nature and Society, I’ve posted occasional updates on my blog as more recent data become available. I believe that the last of these was in 2022 – see Have honey bees declined in Britain? An update of the numbers – so it feels like it’s time for another. And what’s more appropriate than to post this on World Bee Day 2025?!

Rather than the complex, multi-coloured graph that I’ve produced in the past, I’ve decided to streamline the presentation and simply fit a smoothed LOESS line with a 95% confidence ribbon to the (sometimes contradictory) data points, in order to show the overall trend (see the graph above). If you compare it with the 2022 update you’ll see that the general message from the data is the same: a peak in numbers of hives in the late 1940s (which may or may not be an artefact*), then a steep decline into the 1970s and 1980s, followed by recovery from the 1990s onwards. Note that I’ve removed the two very early data points because I don’t think that they are at all accurate.

The most recent data (2015 to 2024) come from the National Bee Unit which relies on beekeepers to submit their own records, but are probably no less accurate than some of the other data that’s available! If we take a close look at that time period we see something interesting – honey bee hive numbers are decreasing:

What are we to make of this? In an analogy with peak oil, why do we seem to have passed ‘peak honey bee’? If this is a real pattern (and only time will tell) I suspect that it’s because of at least two factors. The first is that interest in beekeeping reached a peak in the early 2020s, after which some initial enthusiasts discovered that beekeeping is actually quite a technical and demanding hobby, and gave it up. The second factor is that word has spread that , globally, managed Western honey bees are not declining, and too many bee hives in an area can have negative impacts on other, wild pollinators. This may have impacted those people who were persuaded by “Save the Bee” campaigns to take up the hobby, to give up beekeeping.

There could well be other reasons that I’ve not considered and, as always, I’d be interested in your thoughts – please leave a comment below. I’ll finish by saying that I make no judgement on this. There’s no doubt that there are too many hives in some parts of Britain, especially in London, and if the trend I describe reduces the pressures on wild pollinators, that’s a good thing. At the same time, honey bees are important agricultural pollinators in some circumstances, especially where there’s mass-flowering crops that require huge numbers of pollinating bees to be available over a short time period. And I like honey as much as the next person.

Happy World Bee Day to my readers!

*There’s a long-standing suggestion that beekeepers in the post-war years inflated the number of hives that they kept in order to obtain a larger sugar ration.

Mindful Mow May!

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As April comes to a close, many people with gardens will be considering having a No Mow May in which, to quote Plantlife, you ‘pack away the lawnmower, let wildflowers grow freely and help nature’. On the face of it this is a positive thing and (hopefully) it gets people thinking a bit more about the impact of gardening practices on wildlife. However, I do worry that its message is too simplistic, as I’ll explain in the rest of this post. Let me say at the outset that I’m using the word ‘mindful’ in its sense of ‘paying attention to’, rather than in relation to mental health mindfulness. Though there are certainly connections between lawns and both meanings of this word, for example mindfully watching pollinators in your garden.

I’ve previously written about the garden that Karin and I developed in Northampton, including a ‘defence’ of its lawn. During the lockdown spring and summer of 2020, when I coordinated a loose consortium of scientists to collect standardised data on the flowers and pollinators in their own garden, our lawn was one of the areas that I surveyed. In that year, as every year, we had no intention of not mowing the lawn, but of mowing it in a mindful way that left some flowering patches of the main nectar sources: Dandelion (Taraxacum officinale), White Clover (Trifolium repens), and Daisy (Bellis perennis). It also allowed a patch of Common Ragwort (Jacobaea vulgaris), and the Cinnabar Moths (Tyria jacobaeae) that depend on it, to come back year after year.

In the graph below you can see the nectar production of dandelions, clovers and daisies over the course of the late spring to late summer. For each species, I have multiplied the number of flower heads I counted by the average amount of nectar sugar per flower head from the data collected by the Agriland project. Clover produces 48.97 micrograms of sugar per day, by far the highest amount of the three. Daisy produces the least, just 0.84 micrograms, and dandelion is in the middle with 22.57 micrograms.

Because these species vary in their peak flowering, there’s a continuous supply of nectar in the lawn over this time period and mowing does impact the immediate availability of nectar. Using green shading, I’ve marked the two days when I know for certain the lawn was mown and you can see that there’s an immediate drop in the nectar. Here you can also seen that both dandelions and daisies re-flower quite soon afterwards – it’s not a permanent effect by any means. The same is probably true of clover later in the season, but unfortunately I didn’t record the exact mowing dates.

The important thing to appreciate here is that without mowing, these three species would probably disappear from the lawn because all require that grasses are suppressed in order for them to flourish. Not only that, but most ground-nesting bee species need either very short turf or bare soil in which to nest. And most bees, at least in the UK, are ground-nesting.

The image at the top of this post is from my book Pollinators & Pollination: Nature and Society, and it shows two views of the same grassy, south-facing bank in Kettering, Northamptonshire. I included it because it’s a nice example of the mindful approach to lawn mowing that I am describing: bees are able to nest in the low-cut turf and collect the nectar and pollen from the flowers in the unmown areas. Later in the season that unmown area will be cut. This is referred to as ‘matrix mowing’, which is to say that by cutting some areas and leaving others, you create a matrix of different lawn lengths that has a greater overall benefit than is obtained by either cutting everything at the same time or cutting nothing for a whole month. It’s even better if you have the space to leave some patches unmown for a year or two. That way you create longer grassy areas in which insects can over winter and some bumblebees can nest.

It’s worth mentioning at this point that I know of only one published study that’s assessed the impact on No Mow May on pollinators, and that study was retracted shortly after it appeared. If I’ve missed other studies please do let me know in the comments.

I’ll finish with the Royal Horticultural Society, which was in the news recently with an announcement that it’s collaborated with gardener Monty Don to come up with ‘hard-wearing flower lawn that is good for pollinators, dogs and people’. This is hardly rocket surgery, it’s the sort of diverse, low-input, low maintenance lawn that many of us have been advocating for years, but if it brings these ideas to popular attention, so much the better.

So, consider engaging in Mindful Mow May (and April, and June, and all the other months!) As always, feel free to comment below or get in touch with me via my Contact page.

Is Common Elder an under-appreciated habitat for bats? [updated]

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Regular readers of my blog may recall that I have an obsession with something of an interest in Common Elder (Sambucus nigra) that goes back to my childhood, as I recounted in an article for British Wildlife back in 2022. In that article I mentioned that the larger hollow trunks and branches of elder “can offer nesting opportunities for birds and small mammals”, but didn’t go into detail. The mammals I was thinking of at the time were small rodents, but following a long country walk with Karin recently I wondered whether bats might also make use of these hollows as roosts for breeding and/or hibernation.

I posed this as a question for the bat specialists in the British Ecologists Facebook Group and received several replies, with respondents mentioning that they had encountered Natterer’s Bat (Myotis nattereri), Common Pipistrelles (Pipistrellus pipistrellus), and Brown Long-eared Bat (Plecotus auritus), in hollow elder trees, during summer and autumn surveys.

A couple of people suggested that I check out Arbology’s Look-up Tool for the Bat Tree Habitat Key (BTHK) database which records trees that are used by bats, but to my surprise it returned the following message:

“There are no positive results which match your query.
This does not mean that bats won’t use the feature type in the species and habitat you have selected, but current data suggests that survey effort may be better focused on features which have a proven occupation”. 

The BTHK relies on bat surveyors adding their observations, but clearly no one has submitted records of bats in elder, despite the fact that we know they occur. This concerns me for two reasons.

Firstly, of all of our smaller native woodland edge and hedgerow trees, elder is (in my experience) the one most likely to have significant cavities in their trunks and branches. The specialists in the Facebook Group introduced me to the phrase “if they fit, they sit”, meaning that almost any cavity might contain bats, even quite low to the ground: one respondent mentioned that a friend had found two Common Pipistrelles during an autumn survey, in a dead elder stem less than ten centimeters in diameter at about one metre above ground level.

Secondly, it’s not unusual for old elder trees to be cut right to the ground or even removed completely during work on hedgerows. It’s a neglected, even despised native British tree that, as I noted in that British Wildlife article, is:

“generally considered by naturalists, when it is considered at all, as rather boring, so commonplace that we hardly give it a second glance…[and by some as]…’barely a tree at all, more of a weed'”

Another respondent mentioned that ​tubular structures, such as elder branches, are less likely to be identified as active bat roosts in the absence of bats, as they provide limited shelter and often lack droppings, which tend to fall out, leaving minimal evidence. I’m sure that’s not the whole story, however, I think it’s more likely that small trees generally are overlooked when it comes to habitat for bats: the BTHK has a single entry for Common Hawthorn (Crataegus monogyna) and nothing for Blackthorn (Prunus spinosa), for instance.

In addition to bats, another respondent noted that Willow Tits (Poecile montanus), a species experiencing significant decline and now red-listed in the UK, often nest in elder trunks, where they excavate cavities in decaying wood. That’s yet another reason why we should pay more attention to this most interesting of trees!

My thanks to all of the British Ecologists who replied to my query. As always, feel free to comment or get in touch via my Contact page.

UPDATE: After I posted this on Bluesky, Richard Broughton, author of The Marsh Tit and the Willow Tit, pointed out that elder is also a significant nesting site for Marsh Tits (Poecile palustris), another red-listed species. To quote Richard’s comment:

“Elder is prob[ably] the very best cavity-bearing shrub, far better than hawthorn, hazel, blackthorn (very poor). Important nesting shrub for Marsh Tits & Willow Tits, but only if left to develop old trunks and cavities, not cut. Like Hazel, they self-coppice without management, with new growth from base….in Wytham Marsh Tit studies Elder was the main nest tree/shrub. Though it’s not common/available in woods everywhere. It develops *really* good hollow nest cavities for the small hole-nesting guild, and also very amenable for Willow Tits to excavate. Prob[ably] important in hedges, where holes rare.”

Richard kindly shared a scan from his book showing that for Willow Tits, elder ranks second (after willow and birch) and for Marsh Tits it ranks second after Ash.

Evolutionary implications of a deep-time perspective on insect pollination – a new review just published

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When we think of pollination, we often picture bees buzzing around flowers or butterflies flitting from bloom to bloom. This relationship between plants and pollinators is one of the most well-known interactions in nature. But insect pollination didn’t begin with the colorful flowers we see today. In fact, pollinators were at work millions of years before flowering plants (angiosperms) even existed. In a new review led by Spanish researchers David Peris and Ricardo Pérez-de la Fuente, to which I added a modern ecological perspective, we explored this topic and why it’s relevant to our current understanding of plant-pollinator relationships.

Despite centuries of research on pollination, the fossil record of pollinating insects has only gained serious attention in the past few decades. What palaeontologists have uncovered is reshaping our understanding of pollination’s origins. It turns out that insects were pollinating plants long before flowers evolved—playing a crucial role in the reproduction of ancient gymnosperms, the group of seed-producing plants that includes conifers, cycads, and ginkgos.

Most people assume that insect pollination began with flowering plants, but the evidence tells a different story. Fossilised insects with specialised body structures for carrying pollen—such as hairy bodies or mouthparts adapted for nectar-feeding—have been found in deposits dating back hundreds of millions of years. These early pollinators likely visited gymnosperms, helping them reproduce in a world that looked vastly different from today’s landscapes.

Ancient pollination was driven by a diverse range of insects, many of which are now extinct. The fossil record reveals that various insect groups—including beetles, flies, wasps, and even some long-lost relatives of modern lacewings—were already acting as pollinators long before the first flower bloomed. This means that pollination as an ecological process has far deeper evolutionary roots than many realise.

As plants evolved, so did their pollinators. The rise of flowering plants during the Cretaceous period (around 100 million years ago) transformed pollination systems, leading to the incredible diversity of plant-pollinator relationships we see today. Many of the insect groups that once dominated pollination in prehistoric times have since declined or disappeared, replaced by the bees, butterflies, and other familiar pollinators that thrive in modern ecosystems.

Understanding this long history is essential—not just for scientists, but for anyone interested in biodiversity and conservation. When we focus only on present-day pollinators and plants, we miss a crucial part of the story. The fossil record helps us see how pollination has changed over time, which in turn can offer insights into how today’s ecosystems might respond to environmental pressures such as climate change and habitat loss.

Recognising the ancient history of insect pollination isn’t just an academic exercise—it has real-world implications. If we understand how pollination evolved and adapted to past environmental changes, we can better predict how it might shift in the future. Conservation efforts that aim to protect pollinators today can benefit from a long-term perspective, ensuring that we’re not just responding to recent trends but also considering deep-time ecological processes.

So the next time you see a bee visiting a flower, remember—you’re witnessing the latest chapter in a story that began hundreds of millions of years ago. The relationship between plants and pollinators is far older, more complex, and more fascinating than we ever imagined.

Here’s the reference with a link to the paper. It should be open access, but if you have problems obtaining it, send me a message via my Contact page:

Peris, D., Ollerton, J., Sauquet, H., Hidalgo, O., Peñalver, E., Magrach, A., Álvarez-Parra, S., Peña-Kairath, C., Condamine, F.L., Delclòs, X. & Pérez-de la Fuente, R. (2025) Evolutionary implications of a deep-time perspective on insect pollination. Biological Reviews (in press)

What is happening to wild bees in Britain?

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Recently the Bumblebee Conservation Trust (BCT) reported that, in 2024, British bumblebees experienced their worst year since the BCT started its monitoring campaign. Overall, the numbers of bees were down by more than one fifth, with one of our commonest species, the Red-tailed Bumblebee (Bombus lapidarius) declining a staggering 74%! The cause seems to be the cold, wet spring of 2024 and we have to hope that this is a blip that will not be repeated in 2025. So far the year has been cold and I didn’t see my first queen bumblebee flying until early March. But the very warm weather over the last few days has encouraged bumblebees out of hibernation and plants to start flowering.

Long-term monitoring of the type that the BCT undertakes with its volunteers, is vital if we are to understand how British pollinators are faring. When I compiled the evidence for the chapter entitled ‘The shifting fates of pollinators’ in my book Pollinators & Pollination: Nature and Society, I tried to give a global overview, but also focused on British records, which are probably the best long-term data that is available on trends in pollinators. This information is compiled by the Joint Nature Conservation Committee (JNCC) as part of its annual UK Biodiversity Indicators reports. Each year it produces an indicator showing trends in bees, hoverflies, and the two combined as an overall pollinator trend*. To quote the JNCC website:

The indicator is based on 394 species (158 species of bee and 236 species of hoverfly), and measures change in the number of 1 kilometre grid squares across the UK in which they were recorded in any given year: this is referred to as the ‘occupancy index’.

The bee data comes from the Bees, Wasps and Ants Recording Society (BWARS) and the graph of bee trends that I used in that chapter of my book assessed records up until 2017. It looked like this:

As you can see, the index fluctuated a bit but was on average fairly stable up until 2005, after which there was a sharp decline, then an uptick from about 2014, though still low compared to the 1980 baseline. The overall impression is that bees had a tough time from the early 2000s onward, but things seem to be improving.

Since my book came out in 2021 I’ve given a lot of talks to natural history societies, ran training with consultancies and local councils, and so forth. Each year I update the JNCC graphs in my talks to give the audience the latest information. This is the one I used last year, which took the data up to 2019**:

This looks a bit different – the fluctuations are more pronounced – but overall the trend is similar, though the drop after 2015 is worrying. The impression is that there’s been big (cyclical?) fluctuations in the bee index over time, but its generally always below the 1980 baseline.

Updating the story to 2022 (the most recent available) shows a very different picture:

The impression it gives is that there’s been some modest fluctuations in the bee index, but then from about 2013 onward, the index has massively improved and now wild bees are doing better than ever!

What’s happening here? Why are these three graphs – published over a period of about five years – giving such different impressions of what’s happening to wild bees in Britain? As far as I can tell there’s two main reasons for the changes. The first is that the number of bee species included in the index increased from 137 to 148 to 158. Adding species for which there was previously no or little data is clearly going to have an effect.

The second reason, perhaps more fundamental, is that the method used for calculating the index has been refined, as explained in the technical annex to the study. That’s important because the data underlying the bee index was never collected in a standardised way for the purposes of assessing species’ trends. For this reason the UK Pollinator Monitoring Scheme (PoMS) was developed and it’s interesting to see that the data in the latest PoMS report shows some stability in wild bee abundance from 2017 to 2022:

So the latest data suggests that, for once, there’s some good news in the world of British wildlife. Does this mean that we should be complacent about the state of our wild bees? Absolutely not! As always, the devil’s in the details. The BCT report that I cited at the start of this post provides one level of (worrying) detail. But another is provided by the JNCC’s own statistics. As well as showing the overall trend in the bee index, the analysis digs into what is happening for individual species and provides a helpful summary figure like this:

Clearly many species are doing well, or at least have not changed since the 1980s. But more than one quarter of British wild bees are showing a weak or strong decline over the long term. That’s a clear signal that we need to keep on with our efforts to support wildlife and enhance our strategies to improve the state of nature in Britain.

As always, feel free to comment on the post or get in touch via my Contact page.

My sincere thanks to all of the volunteer naturalists who collect the data used by JNCC and PoMS – the task of assessing trends in wildlife would be impossible without your commitment!

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*Why JNCC does not include butterflies – which are assessed separately – in this overall trend is unclear to me, as we know that they can be important pollinators for some plants – see my blog post: ‘Butterflies, bumblebees and hoverflies can be equally effective pollinators of some plants says a new study‘.

**The data in the JNCC report is always a couple of years behind the publication date.

How urban spaces support pollinators – a new study just published

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Bees play a vital role in pollination, supporting both natural ecosystems and our food supply. However, their numbers are declining globally due to multiple threats—including urbanisation. As cities expand, understanding how different habitats within urban areas affect pollinator populations is crucial for conservation efforts and for supporting urban and peri-urban agriculture. It’s a topic to which I devoted whole chapters in my books Pollinators & Pollination: Nature and Society and Birds & Flowers: An Intimate 50 Million Year Relationship.

The latest paper from Muzafar Sirohi‘s PhD thesis has just been published in the journal Urban Ecosystems. It follows on from his two other recent papers on plant–bee interactions and resource utilisation and how the timing of emergence of solitary bees varies between urban and non-urban settings.

This element of Muzafar’s work explored how solitary and primitively eusocial bees (those that live alone or in simple social groups) respond to different aspects of city landscapes. He examined local habitat factors such as floral diversity, bare soil availability, and sunlight exposure, alongside broader urban features like green spaces, roads, and paved areas.

The findings highlight that small-scale habitat conditions—especially the variety of flowering plants and access to sunlight—had a greater influence on bee diversity and abundance than overall habitat size. While larger landscape features, such as urban green spaces, played a role at a broader scale, even small patches of wild vegetation and roadsides were found to be important for bees.

These results challenge the idea that bees need large, uninterrupted green spaces to thrive. Instead, even fragmented urban habitats, when managed thoughtfully, can support pollinators. By planting diverse flowers, preserving patches of wild vegetation, and maintaining sunlit areas, cities can become havens for these essential insects.

Simple changes—like creating wildflower-rich roadside verges or maintaining natural pockets of greenery—can make a significant difference. As urbanisation continues, ensuring that bees have the resources they need to survive will be key to supporting biodiversity and maintaining the critical pollination services they provide.

Here’s the reference with a link to the published study; if you are not able to access it, send me a request for a PDF via my Contact page:

Sirohi, M.H., Jackson, J. & Ollerton, J. (2025) Influence of urban land cover and habitat quality on wild bees. Urban Ecosystems 28:78 – https://doi.org/10.1007/s11252-025-01687-6

Here’s the abstract:

Solitary and primitively eusocial bees are important pollinators of plants, which are experiencing a global decline. Urbanisation is one of the contributing factors to this decline. It is crucial to understand the complex community dynamics of solitary and primitively eusocial bees in urban areas as urbanization grows globally. For bee communities, the local habitat as well as the surrounding urban landscape play an important role. The study considered four local habitat variables: habitat size, floral species richness, bare soil and shade. Moreover, five common land cover types (green space, buildings, roads, car parks, and paved surfaces) were assessed at multiple spatial scales from 40 m to 200 m from the centre of the sites with 20 m steps, analysing their potential impacts on the bee community. The study found a greater effect of local habitat compared to landscape variables at a smaller spatial scale. However, landscapes affected the bee community at larger spatial scales. The size of the habitat did not affect the bee community in urban areas. However, habitats with a higher number of plant species and exposed to sunlight attracted relatively more bees. This study suggests that urban areas are capable of conserving solitary and primitively eusocial bees. Although green space is important for the dispersal of species at larger landscape scales, small patches of wild, leftover vegetation and roadsides are equally important for bees. The management of bee friendly open vegetation with wildflowers would be beneficial for the successful conservation of solitary and primitively eusocial bees in urban areas.