Tag Archives: Nature conservation

Edible Apocynaceae: a new global synthesis of diversity, conservation and pollination just published – and a personal landmark for me!

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This year – 2026 – marks the 40th anniversary of my first publication. Forty years. Imagine that – I certainly can’t! It feels like a long time ago, a distant memory, another life. I was 21 and I hadn’t even begun my undergraduate degree. After a less-than-successful time at school I decided to complete a Higher National Diploma (HND) qualification in Applied Biology at Sunderland Polytechnic (now the University of Sunderland) that I hoped would get me a place on a degree course. As it turned out, it did, but during my HND I completed a research project which (with the encouragement of my then supervisor, the late cactus expert Geoff Swales*), was subsequently published in December 1986 as “Adaptation to arid environments in the Asclepiadaceae” in the British Cactus and Succulent Journal.

That was the modest start of a botanical love affair with asclepiads (now subsumed into the family Apocynaceae) that has persisted to this day and resulted in over 20 research papers, chapters, and more general articles, plus appearances in both of my books.

The latest of these papers is published today and, as well as being a 40 year milestone for me, it’s a paper that I am inordinately proud of, as it represents an amazing coalescence of ethnobotany, taxonomy, conservation, biogeography, cultural science, and pollination ecology. And I managed to sneak in a citation of the 1986 paper that started the whole thing!

This paper is the first global review of the diversity of edible species in a family that is usually considered to be highly toxic and produces a lot of sticky latex to deter herbivores. Yet that reputation turns out to be only part of the story. Our survey found no fewer than 440 edible species of Apocynaceae worldwide, which works out at about 7.7% of the family (and is definitely an under-estimate). They occur across all of the major evolutionary lineages of the family, and in most of the main biogeographic regions where these plants grow.

What people eat is also far more varied than you might expect. Fruits are the commonest edible part, but roots and tubers are also important, and in different places people consume leaves, stems, flowers, nectar, latex, bark and even wood ash used as a condiment. That diversity is not random: our analyses show clear phylogenetic and geographic patterning in which parts are eaten. In other words, both evolutionary history and regional cultural practices help to shape how Apocynaceae are used as food.

One especially interesting result is that edible Apocynaceae appear, on current evidence, to be less threatened than non-edible members of the family. But that comes with a big health warning: more than 80% of species, edible or otherwise, have never been properly assessed for conservation status. So there is still a huge amount that we do not know.

The same is true for pollination. Many of these plants depend on animal pollinators to produce the fruits and seeds that people eat, yet pollination data are missing for most edible species, including about 90% of those whose edible parts are directly pollinator-dependent.

For me, that is one of the most striking messages of the paper. Hidden inside a family best known for poisons and medicinal compounds is a substantial, globally distributed food resource, much of it tied to local knowledge and wild harvesting. It is a reminder that botanical and cultural diversity, conservation, and pollination ecology are all bound up together. And, as a nice bonus, the study even uncovered an unexpected taxonomic surprise in China, where one edible species turned out to belong in an entirely new genus, Kushengia. The edible flowers of Kushengia sinensis are shown in the image at the top of this post – lightly boiled, stir fried with garlic, and thoroughly delicious!

Here’s the reference with a link to the paper, which is unfortunately pay-walled. If anyone wants a copy, send me a request via my Contact page:

Ollerton, J., Albuquerque-Lima, S., Liede-Schumann, S., Galetto, L., Endress, M.E., Forster, P.I., Torres, C., Fishbein, M. & Ren, Z.X. (2026) Edible Apocynaceae: phylogeny, biogeography, conservation and pollination insights from a global synthesis. Taxon 75: e70131

*It goes without saying that I’m incredibly grateful to Geoff and the other teachers and supervisors who, during the course of my education, encouraged me in my studies. During one lab session with Geoff we were each given a cactus seed and asked to study it under a microscope and draw it. Afterwards I pocketed the seed, took it home, and germinated it. That cactus – a specimen of Parodia (Notocactus) mammulosus – is still growing on my windowsill, a living reminder of a great mentor.

Connecting soils and pollinators: the ProPollSoil project kicks off in Germany!

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The ProPollSoil project officially got underway on 1st October, and this week (16th–20th November) our consortium gathered in Freising, Germany, for the kick-off meeting hosted by the Technical University of Munich. It was an inspiring start: dozens of experts from across Europe coming together to explore two big questions: How does the health of our soils shape the fate of pollinators? And how do pollinators influence soil health?

Most people think of pollination as something that happens in the air or on flowers, but for many species the story begins underground. Thousands of bees, hoverflies, beetles and wasps depend on soil to nest, overwinter, or complete parts of their life cycle. For example, around half of the solitary bee species in Britain and Ireland are what we term “ground nesting” and make their nests in different types of soil. Yet soil conditions—structure, temperature, contaminants, farming practices—are changing rapidly. As part of the EU’s Mission Soil programme, ProPollSoil aims to understand these hidden links so we can better protect the pollinators that support our food systems and ecosystems.

The project brings together specialists in entomology, soil science, ecology, modelling, agriculture, economics, and communication, forming a truly interdisciplinary team. Through desk-based reviews, fieldwork, lab experiments, monitoring and advanced modelling techniques, we’ll be investigating how soil influences pollinator survival and what we can do to improve it.

ProPollSoil is built around six key goals, including identifying the soil conditions that help pollinators thrive, testing innovative ways to monitor soil-dependent species, evaluating how different land-use and farming practices affect pollinators, and developing practical soil-management solutions—from reduced tillage to cleaner soils—that can slow or reverse their decline.

My own role mainly focuses on understanding the state of our current knowledge of the biology and ecology of soil-dependent pollinators and their interactions with soils, other invertebrates, and plants. I’ll also be working on integrating information about pollinators’ soil dependencies into the European Atlas of Plant-Pollinator Associations (EuroAPPA), part of the related Butterfly Project, whose kick-off meeting I documented on the blog earlier this year.

Together, these efforts will help build a clearer, more complete understanding of how life belowground supports life aboveground. It’s an exciting journey, and we’re only just getting started!

My sincere thanks to all of the ProPollSoil consortium members whose passion and expertise made for a stimulating few days in Germany. And a special shout-out for the team from Poland who brought with them some delicious, PropPollSoil branded sweets:

Book review: “Urban Plants” by Trevor Dines

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Earlier this year I received an unexpected invitation from Bloomsbury Publishing to attend a book launch at Philip Mould’s gallery in London. Looking at the details I immediately said yes, because it combined three of my passions: natural history, art, and books! Not only that, but the topic of the book was one very close to my heart – the wildlife of our towns and cities.

Urban Plants is the latest addition to Bloomsbury’s British Wildlife Collection, a stunningly produced series that has set a new benchmark for natural history literature in this country. The author, Trevor Dines, formerly worked for the charity Plantlife, and is a real authority on urban botany. My expectations for this book were very high! So on the day of the book launch, Karin and I trundled down to the capital and spent part of the day at the National Gallery where, among other things, we enjoyed an exhibition by José María Velasco. As well as being a superb documenter of the 19th century landscapes of Mexico, Velasco was also profoundly interested in botany. We’d not planned it that way, but it was a nice coincidence.

The book launch itself was well attended and I found myself catching up with a few familiar faces from the world of British wildlife, and Trevor (whom I’d corresponded with but never met) treated us to a short reading:

I took the opportunity to buy a copy, had a quick chat with Trevor, who kindly signed the book, and then we headed back to catch a train.

So what do I think of Urban Plants?

It’s actually hard to praise the book too much without sounding unnecessarily gushy! But it really is one of the best books that I’ve read for a long time. In part that’s because it stirs deep emotions of me as a child, taking my first faltering steps into the world of natural history on the bomb sites and post-industrial landscapes of my native Sunderland. But it’s more than that: the author writes with elegance and authority on a topic about which he’s deeply passionate, and this comes through on every one of the amply illustrated pages. Trevor should be congratulated on producing a book that will be the go-to reference on the topic for many years to come.

And an important topic it is too: there’s no doubt naturalists who will sneer at the idea of urban botany, but (as the author points out) for many people in this country, the plants that they see every day in their home towns are almost their only connection to wildlife. For that reason alone it’s a subject to be taken seriously, and if a book like this can inspire more people to take a closer look at the plants with which we share our streets, roofs and walls, so much the better.

So do yourself a favour and take a walk with Trevor through the complex ecology and botany of built-up British landscapes. I learned a lot from Urban Plants and I highly recommend it as an addition to anyone’s Christmas list.

Pollinators need more space and 10% habitat is not enough says a new study just published in Science

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Pollinators such as wild bees, butterflies, and hoverflies are in trouble worldwide. A major new study, published in Science and led by Gabriella Bishop and other scientists at Wageningen University & Research, shows that the oft-quoted figure of 10% semi-natural habitat in farmland landscapes is far too little to safeguard pollinators. Instead, the evidence points to a need for somewhere between 16% and 37% habitat cover, depending on the type of pollinator, if we are serious about halting declines. Suitable habitats include hedgerows, patches of woodland, species-rich grasslands, and flowering margins, and as a general rule, hoverflies need less of it whilst bumblebees and butterflies require more.

I was fortunate to play a part in this global assessment, contributing an unpublished dataset collected with my former PhD student, Sam Tarrant, who studied plant-pollinator interactions on restored landfill and established grassland sites. Seeing those data joined with dozens of other studies from around the world underlines something we have known for years: no single dataset, however carefully gathered, can give us the whole picture. To really understand what is happening to biodiversity—and to design conservation solutions that work—we need these kinds of global, mega-author syntheses that draw together evidence from many landscapes, taxa, and approaches.

The message from this analysis is stark but hopeful. More habitat means more pollinators, across all groups. Richer habitats with abundant flowers give an additional boost, but the overriding priority must be to increase the sheer area of natural habitat in farmed landscapes. Small-scale fixes like wildflower strips offer short-term benefits, but without enough space they can’t deliver recovery at scale. Long-term, secure habitat creation—on the order of decades, not seasons—is what pollinators, farmers, and ecosystems need.

Although the policy debate in Europe provided the backdrop for this study, the lessons (and the data) are global. Wherever agriculture dominates, the health of pollinator populations—and by extension our food security and biodiversity—depends on our willingness to give these insects the space and quality of habitat they require.

Looking ahead, we need to think bigger and work together. That means more international collaborations, more sharing of data, and more commitment to long-term solutions that transcend borders. The image at the start of this post is from my trip back to China in July this year. I deliberately chose it because, as you’ll see from the map below which is taken from the paper, there was no suitable data available for the study from that country. Or from Africa. Or Australasia. Or from most of tropical South America. That shows that as pollination ecologists we need to coordinate more in advance on these types of syntheses, and maximise the value of the kinds of data that we collect. The main take away from this study, however, is that if we want to reverse the declines in biodiversity, scientists, policymakers, businesses, farmers, and citizens all have a role to play. Pollinators remind us that nature is interconnected and global—our conservation efforts must be, too.

Here’s the full reference with a link to the study:

Bishop, G.A., Kleijn, D., Albrecht, M., Bartomeus, I., Isaacs, R., Kremen, C., Magrach, A., Ponisio, L.C., Potts, S.G., Scheper, J., Smith, H.G., Tscharntke, T., Albrecht, J., Badenhausser, I., Åström, J., Báldi, A., Basu, P., Berggren, N., Beyer, N., Blüthgen, R., Bommarco, B.J., Brosi, H., Cohen, L.J., Cole, K.R., Denning, M., Devoto, J., Ekroos, F., Fornoff, B.L., Foster, M.A.K., Gillespie, J.L., Gonzalez-Andujar, J.P., González-Varo, J.P., Goulson, D., Grass, I., Hass, A.L., Herrera, J.M., Holzschuh, A., Hopfenmüller, S., Izquierdo, J., Jauker, B., Kallioniemi, E.P., Kirsch, F., Klein, A.-M., Kovács-Hostyánszki, A., Krauss, J., Krimmer, E., Kunin, B., Laha, S.A.M., Lindström, Y., Mandelik, G., Marcacci, D.I., McCracken, M., Monasterolo, L.A., Morandin, J., Morrison, S., Mudri Stojnic, J., Ollerton, J., Persson, A.S., Phillips, B.B., Piko, J.I., Power, E.F., Quinlan, G.M., Rundlöf, M., Raderschall, C.A., Riggi, L.G.A., Roberts, S.P.M., Roth, T., Senapathi, D., Stanley, D.A., Steffan-Dewenter, I., Stout, J.C., Sutter, L., Tanis, M.F., Tarrant, S., van Kolfschoten, L., Vanbergen, A.J., Vilà, M., von Königslöw, V., Vujic, A., WallisDeVries, M.F., Wen, A., Westphal, C., Wickens, J.B., Wickens, V.J., Wilkinson, N.I., Wood, T.J., Fijen, T.P.M. (2025) Critical habitat thresholds for effective pollinator conservation in agricultural landscapes. Science 389: 1314-1319

Here’s the abstract:

Biodiversity in human-dominated landscapes is declining, but evidence-based conservation targets to guide international policies for such landscapes are lacking. We present a framework for informing habitat conservation policies based on the enhancement of habitat quantity and quality and define thresholds of habitat quantity at which it becomes effective to also prioritize habitat quality. We applied this framework to insect pollinators, an important part 5 of agroecosystem biodiversity, by synthesizing 59 studies from 19 countries. Given low habitat quality, hoverflies had the lowest threshold at 6% semi-natural habitat cover, followed by solitary bees (16%), bumble bees (18%), and butterflies (37%). These figures represent minimum habitat thresholds in agricultural landscapes, but when habitat quantity is restricted, marked increases in quality are required to reach similar outcomes.

Book review: ‘The Dales Slipper: Past-Present’ by Paul Redshaw

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Tomorrow I head to China for two months of writing, field work, talks, and student discussions at the Kunming Institute of Botany in China, a follow-up to the work that I did last year. It feels appropriate, therefore, to be reviewing a book devoted to a western European outlier of a group of orchids (the ‘lady’s slippers’) that have one of their centers of diversity in that country.

In The Dales Slipper: Past-Present, author Paul Redshaw focuses on ‘the’ Lady’s Slipper (Cypripedium calceolus), an almost mythological species in British botany, due to its extreme rarity, the secrecy and protectiveness about where it grows, and its tendency to be dug up by unscrupulous orchid collectors. And a fascinating (if sometimes frustrating) read it is too!

The fascination of the book lies with Paul’s ability to sleuth previously unknown facts from local people who were witnesses to the rediscovery and subsequent protection of what was thought to be the last colony of the species in Britain. Protection was afforded by ‘The Guardians’ who (of course) met in a pub and were sworn to secrecy and (of course) fell out when personalities and priorities clashed. They were replaced (ousted?) by a more formal ‘Cypripedium Committee’ that still exists today, but who (if the author is to be believed) are even more secretive than The Guardians!

Drawing on newly uncovered archives, personal testimonies, and previously unseen images, the book details the decades-long efforts – marked by secrecy, dedication, and conflict – to protect the species from extinction. It stands as the first comprehensive and fully referenced account of this remarkable conservation journey

It makes a compelling story of the kind I can imagine being a successful comedy-drama for television – think Detectorists with hand lenses.

I mentioned that the book was a frustrating read, too. That’s partly because there’s a big cast of characters, some of whom have the same names, and it’s easy to lose track of who they are and what they did, and when. Paul does provide a helpful list of the protagonists but I found myself feeling a bit lost in places. That’s not helped by the fact that the book would have benefited from professional editing to smooth the rough edges.

These minor gripes aside, The Dales Slipper will interest anyone looking for a deep dive into British botanical history via the world of one of our rarest and most iconic wild plants.

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 convinced 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.

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.