Category Archives: Climate change

Pollinators are allies in the fight against climate change: a new commentary just published in New Scientist

Over the past few months I’ve been thinking a lot about the relationship between the “Climate Emergency” (CE) and the “Ecological Emergency” (EE), and how they overlap considerably in terms of causes and solutions, but that the priorities of the CE often trump those of the EE. One of the outcomes of this has been a commentary that’s been published in New Scientist this week. It’s free to access – here’s the link:

It’s extracted from a much longer article that discusses the role of pollinators in relation to climate change. Hopefully that will be published in the not too distant future.

The other thing that’s happened this week is that, in my role as Visiting Professor of Biodiversity at the University of Northampton, I was asked to take part in a webinar that’s one of a series being produced in support of the Levelling Up Goals. The LUGs, modelled on the UN’s Sustainable Development Goals (SDGs) have cross-party support in Parliament and aim to bring economic prosperity to those parts of the country that have lagged behind in recent decades. The “Green Economy” is seen as central to this.

The webinar was recorded and you can view it here:

It was interesting and I learned quite a bit, for example about how the government is investing the state pension pot in sustainable energy projects. The format of the webinar, however, with the chair asking individuals a question and each of us responding, was a little frustrating as there was no real opportunity to counter statements being made, particularly by the MP for Hexham.

Yesterday Karin and I had out first COVID-19 vaccination; today we both feel a little under the weather, but it will pass. It’s certainly better than the alternative!

Climate change history affects contemporary pollination systems – a new study just published

Illustration of Curatella americana and its pollinators by Pedro Lorenzo

The distribution of plants, animals and other organisms that we see around us is clearly influenced by climate: all species have limitations in terms of temperature, rainfall, etc., that affects where they can live and reproduce. As well as these contemporary “climatic niches” however, there are much more subtle effects of historical climate on species, and the ways in which they interact with one another. These are harder to study because it requires us to know about what climatic conditions were like in a particular region thousands or millions of years ago. But as our knowledge of paleoclimates grows, we can apply it to understand how contemporary ecology is shaped by the past. This in turn may tell us how species will react to future climate change.

In a new study that I’ve just published with Brazilian, Danish and American colleagues, we’ve shown that the frequency with which a South American savannah tree self-pollinates is determined mainly by the climatic stability experienced by a population since the Last Glacial Maximum. In contrast, and perhaps surprisingly, the current diversity and abundance of pollinators plays a much smaller role in how often plants self-pollinate.

The work was led by André Rodrigo Rech and formed part of his original PhD research. Here’s the full citation:

Rech, A.R., Ollerton, J., Dalsgaard, B., Jorge, L.R., Sandel, B., Svenning, J.-C., Baronio, G.J. & Sazima, M. (2021) Population-level plant pollination mode is influenced by Quaternary climate and pollinators. Biotropica (in press)

The abstract is below, first in English then in Portuguese. If anyone wants a PDF please add a comment or send me a message via my Contact page.


Patterns in ecology are the products of current factors interacting with history. Nevertheless, few studies have attempted to disentangle the contribution of historical and current factors, such as climate change and pollinator identity and behavior, on plant reproduction. Here, we attempted to separate the relative importance of current and historical processes on geographical patterns of the mating system of the tree species Curatella americana (Dilleniaceae). Specifically, we asked the following: (a) How do Quaternary and current climate affect plant mating system? (b) How does current pollinator abundance and diversity relate to plant mating system? (c) How does mating system relate to fruit/seed quantity and quality in C. americana? We recorded pollinators (richness, frequency, and body size) and performed pollination tests in ten populations of C. americana spread over 3,000 km in the Brazilian savannah. The frequency of self‐pollination in the absence of pollinators was strongly influenced by historical climatic instability and not by present‐day pollinators. In contrast, seed set from hand‐cross and natural pollination were affected by pollinators (especially large bees) and temperature, indicating the importance of current factors on out‐cross pollination. Two populations at the Southern edge of the species’ distribution showed high level of hand‐cross‐pollination and high flower visitation by large bees, but also a high level of autogamy resulting from recent colonization. Our results indicate that historical instability in climate has favored autogamy, most likely as a reproductive insurance strategy facilitating colonization and population maintenance over time, while pollinators are currently modulating the level of cross‐pollination.


Os padrões em ecologia são o produto de fatores contemporâneos interagindo a partir de uma bagagem histórica. Apesar desse reconhecimento, poucos estudos se ativeram em separar as contribuições dos fatores históricos e atuais como o clima, a identidade e comportamento de polinizadores sobre a reprodução de plantas. Neste trabalho nós decompomos a importância relativa dos processos contemporâneos e históricos no padrão geográfico do sistema reprodutivo da árvore comum no Cerrado, Curatella americana (Dilleniaceae). Especificamente nós perguntamos a) como o clima do presente e do quaternário afetam o sistema reprodutivo? b) Como a abundância e diversidade de polinizadores afeta o sistema reprodutivo da planta atualmente. c) Como o sistema reprodutivo se relaciona com a quantidade e qualidade dos frutos produzidos em C. americana? Para responder estas questões, nós registramos os polinizadores (riqueza, frequência e tamanho corporal) e realizamos testes de polinização em 10 populações de C. americana distribuídas em mais de 3.000 km de Cerrado no Brasil. A frutificação com autopolinização foi fortemente influenciada pela instabilidade climática do passado e não teve relação com os polinizadores no presente. Em contraste, a frutificação com polinização cruzada manual e natural foi afetada pelos polinizadores (especialmente abelhas grandes) e pela temperatura atual, revelando o papel de fatores ecológicos sobre a polinização cruzada. Duas populações na borda sul da distribuição de C. americana apresentaram alto nível de frutificação com polinização cruzada manual e altas taxas de visitação floral por abelhas grandes, mas também apresentaram alto nível de autogamia interpretadas como resultado da recente colonização dessas áreas. Nossos resultados indicam que a instabilidade climática do passado promoveu a autogamia como uma estratégia de segurança reprodutiva capaz de facilitar a colonização e manutenção de populações nesses locais com polinizadores imprevisíveis. Em contrapartida, nos locais com disponibilidade de polinizadores a polinização cruzada foi intensificada revelando a como processos históricos e contemporâneos atuam de forma sinérgica sobre o sistema reprodutivo das plantas.

Why did I write the book? An interview with NHBS

The nice people at NHBS recently did a wide-ranging interview with me about my new book Pollinators & Pollination: Nature and Society and what led me to write it. It covers a lot of ground, including climate change, food security, the UK Pollinator Monitoring Scheme, and growing up in Sunderland.

Here’s the link:

Why are bees like Bactrian camels? Because they both have two humps!

It was eminent bee biologist Charles Michener who first* pointed out that there was something odd about the global distribution of bees. In his 1979 paper Biogeography of the bees he writes:

“unlike many groups which abound in the tropics, bees attain their greatest abundance in warm temperate areas”

Think about that for a moment: in contrast to most other groups of insects, birds, mammals, flowering plants, fish, indeed the majority of the Earth’s biodiversity, bees are NOT generally at their most species rich in tropical areas. Rather, we have to move north and south of the equator to find them at their highest diversity. This is an odd pattern of distribution for such a successful (> 20,000 species), globally widespread and ecologically important group of organisms.

Some 15 years ago I was inspired by Michener’s comments when, together with colleagues Steve Johnson and Andrew Hingston, we wrote a chapter called Geographical variation in diversity and specificity of pollination systems for the 2006 Waser & Ollerton edited volume Plant-pollinator Interactions: from Specialization to Generalization. In that chapter we presented a rough analysis of how bee diversity per unit area in different countries changes with latitude. This, and a follow-up that appeared in my 2017 Annual Review of Ecology, Evolution and Systematics paper, confirmed Michener’s view that there’s an unusual relationship between bee diversity and latitude, with peak species richness outside of the tropics, in warm, dry environments.

What I really hoped over this time was that some serious bee biologists would follow up Michener’s insights and produce a full analysis of how bee diversity changes across the planet. Yesterday that hope was realised when Michael Orr, Alice Hughes, Douglas Chesters, John Pickering, Chao-Dong Zhu and John Ascher published the first analysis of bee diversity across the whole planet, and its underlying causes, in their open-access paper Global Patterns and Drivers of Bee Distribution.

Their analyses are based on a data set of >5,800,000 records of where bees occur and it’s been an incredible achievement to bring all of that together into a planet-wide view of where bees are found, and why. I highly recommend that you download and read it, it’s an impressive piece of work.

What have camels got to do with all of this? Well, as the authors show in their paper (from which the image above is taken), if you graph up the increase in bee species richness with latitude from the poles in each hemisphere, you get two humps at about 35 degrees north and south of the equator: like a Bactrian camel. In contrast, as I noted above, if you were to do the same for for most other species you’d get a single hump at the equator: like a dromedary camel.

One of the key drivers of this bimodal pattern seems to be the amount of rainfall in an environment – bees do not like it too wet, in contrast to their relatives the ants which do show the more typical tropical peak in diversity. As the authors put it:

“humidity may play a key role in limiting bee distribution, such as through spoilage of pollen resources”

One of the implications of this for the biogeography of plant-pollinator interactions is that we might expect there to be a greater diversity of different types of pollinators in areas where bees are not so abundant. And indeed that is exactly what we find: in that Ollerton, Johnson and Hingston book chapter I mentioned we showed that there’s a step-change in the diversity of functionally specialised pollination systems as one moves from the sub-tropics into the tropics. There could be many reason for that but I suspect that one is a relative lack of bees compared to the number of plants species; thus you get tropical “oddities” such as specialised cockroach pollination in some plants.

Orr et al.’s paper is a milestone in bee biogeography and opens up new opportunities for conserving these insects, and their vital relationships with the flowering plants. To give just one example: these analyses provide a framework for predicting bee diversity hotspots in parts of the world that have been poorly explored by bee taxonomists, but which are nevertheless severely threatened by habitat degradation and conversion to agriculture. It could also be used for predicting how climate change might affect future bee distributions, especially in parts of the world that are expected to become wetter. I’m looking forward to seeing how the team’s work develops in the future.


*It’s always risky to state “first”, but Michener was certainly the first that I am aware of. Let me know if you’ve come across any precedents.

Get a 30% discount if you pre-order my new book Pollinators & Pollination: Nature and Society


In the next few months my new book Pollinators & Pollination: Nature and Society will be published.  As you can imagine, I’m very excited! The book is currently available to pre-order: you can find full details here at the Pelagic Publishing website.  If you do pre-order it you can claim a 30% discount by using the pre-publication offer code POLLINATOR.

As with my blog, the book is aimed at a very broad audience including the interested public, gardeners, conservationists, and scientists working in the various sub-fields of pollinator and pollination research. The chapter titles are as follows:

Preface and Acknowledgements
1. The importance of pollinators and pollination
2. More than just bees: the diversity of pollinators
3. To be a flower
4. Fidelity and promiscuity in Darwin’s entangled bank
5. The evolution of pollination strategies
6. A matter of time: from daily cycles to climate change
7. Agricultural perspectives
8. Urban environments
9. The significance of gardens
10. Shifting fates of pollinators
11. New bees on the block
12. Managing, restoring and connecting habitats
13. The politics of pollination
14. Studying pollinators and pollination



Ecologists in a time of COVID-19


Yesterday I was involved in what’s likely to be be my last face-to-face teaching and meetings from some weeks, possibly months.  In the morning my colleague Duncan McCollin and I watched our final year students take part in an assessed debate that pitted two sides against one another to argue whether or not Brexit will have a negative effect on biodiversity.  The students did very well, they had a great grasp of the issues and the facts and figures.  The end result was very much a draw:

2020-03-16 10.35.33

Teaching at the University of Northampton will go online from the end of the week and a field trip for our first year undergraduates that we had planned for this Thursday has been pulled.  Our annual Tenerife Field Course has also been cancelled: this will be the first year since 2003 that I have not visited the island and it’s going to leave a hole in my long-term data sets.  Perhaps the universe is telling me that it’s time to write them up for publication?

Last week I did a quick vox pop on Twitter to ask how COVID-19 has affected ecology field work at other universities:

The response was interesting and it’s clear that overseas field courses have been massively impacted.  Following the UK Government’s advice yesterday about limiting social contact it seems that local field work for student groups will also be affected.  Hopefully those undertaking individual field work, especially PhD and postdoctoral researchers, will still be able to carry out their data collection.  Do let me know in the comments if it’s affecting your work.

There were also some Twitter responses from professional ecological consultants pointing out that they may not be able to carry out surveys of sites for planning and development purposes.  This is yet another way in which COVID-19 is going to impact our economy.

Following the student debate, Duncan and I headed out to catch up with a meeting of the steering group of the Chequered Skipper Reintroduction Project   We missed the morning’s presentations but arrived in time for the lunch and a short field trip:

2020-03-16 14.25.51

The location of the reintroduction is still being kept secret, as is a second site where a further reintroduction of butterflies from the Belgium population is being considered.  However there was much discussion as to whether restrictions on travel means that this would have to be delayed until next year.

On the way to that site, during a 15 minute drive, we spotted seven red kites.  They are now so common that seeing these amazing birds hardly requires comment.  But we should never forget what an incredibly successful conservation story this has been.  To cap it all, when we arrived at the site I had the pleasure of meeting Karl Ivens, one of the main drivers behind the reintroduction of red kites to Northamptonshire. He now estimates the regional population to be a couple of thousand birds.  The guy deserves a statue, or at least a blue plaque on his house!

On the way home I was thinking about my next blog post and what to write, and whether or not to bring the pandemic into it.  There’s a lot of information, and misinformation, about COVID-19 online and I’m not qualified to add to that: I’m not an epidemiologist.  However I’d like to link to a few things I think are worth reading.

Over at the Dynamic Ecology blog, Brian McGill has posted an open thread on ecologists discussing the coronavirus pandemic.  There are some interesting contributions in the comments, particularly around the response of the UK Government to the crisis.  I was struck by Jeremy Fox’s comment that Britain has some brilliant epidemiological modelers and that “even if you don’t think much of Boris Johnson or his senior advisers, the modelers who are feeding them information and advice are intellectually honest, hardworking, care deeply about protecting the public, and are as good at their jobs as anybody in the world.”  As I pointed out in a reply, this is undoubtedly true, but a lot depends on whether the government is willing to implement that advice. And its track record so far is not inspiring: for years it ignored expert advice on the effects of badger culling on the spread of bovine TB and continued to kill badgers. It’s only just reversed that decision.  Let’s hope that they have learned from that experience.

I am also hoping that there will be at least one positive outcome from the current pandemic on top of recent extreme weather patterns linked to climate change (for example the drought and fires in Australia that I blogged about in January).  I hope that it serves to  remind the public, governments and large corporations just how dependent on the environment our society is.  Despite our advanced technologies, we are incredibly sensitive to disruptions in the natural world.  As this old piece from the New York Times points out: “most epidemics — AIDS, Ebola, West Nile, SARS, Lyme disease and hundreds more that have occurred over the last several decades — don’t just happen. They are a result of things people do to nature“.   That was in 2012, long before COVID-19 was discovered.  To update this, check out the Wildlife Conservation Society’s ongoing series of articles about the relationship between our destruction of natural habitats, the trade in illegally (and legally) hunted animals, and emerging diseases such as COVID-19.

I realise that I’m fortunate and that there’s a lot that I can do by working from home.  For the next few weeks I’ll be doing just that, supporting students online, completing grant and manuscript reviews, having Zoom/Skype meetings, and completing the book that I am writing.  Stay safe everyone.

Forest restoration for climate change: don’t forget the pollinators and seed dispersers

2020-02-07 09.29.47

There’s been much discussion in the news and online recently about seed collecting, habitat restoration, and tree planting as a way of storing carbon in an effort to reduce the effects of climate change.  This is one of the (many) elements proposed by the recent Drawdown Framework.  In fact their “Table of Solutions” ranks tropical forest restoration in the top 5 to 10 ways of reducing CO2 in the atmosphere, and temperate forest restoration and planting in the top 20.

At one end of the spatial scale, Markus Eichhorn relates the story of his father’s obsession with collecting oak seedlings to reforest the local countryside.  At the other, there’s some very high profile forest restoration schemes going on at the moment; here’s a couple that immediately come to mind:

Grain for Green – China’s attempt to restore vegetation to abandoned farmland to reduce soil erosion and flooding.  According to the Wikipedia entry “Grain for Green has involved 124 million people in 1,897 counties in 25 provinces……. By 2010, around 15 million hectares of farmland and 17 million hectares of barren mountainous wasteland were converted back to natural vegetation”.

Great Green Wall – a multinational initiative in Africa aimed at restoring the vegetation on the southern edge of the Sahara to combat desertification and mitigate climate change.

Several countries have also made a great deal of noise about marshaling huge public efforts to plant hundreds of millions of trees in a single day,  for example India and Ethiopia.

These big schemes are all well and good: they generate a lot of publicity for actions on climate change and a warm, fuzzy feeling that governments and people are Doing Something.  But there’s a couple of problems.  First of all, planting trees is not enough: we could not plant enough trees in the world to reduce CO2 to pre-industrial levels.  Secondly, planted trees require nurturing.  It is not enough just to put in some young plants and hope for the best; a high proportion of trees die even when well looked after.  If they are just planted and ignored, who knows how many will survive?

However habitat restoration is important; it’s not a silver bullet solution to climate change, but it is part of our toolbox of Things We Can Do.  Just as importantly, restoring habitats provides more opportunities for species to move in response to changing climates, and to recolonise areas from where they have been extirpated.  And of course diverse, functioning ecosystems support human societies in ways both tangible and unquantifiable.

With all of this in mind I was interested to read a piece by John Carey in PNAS entitled   “The best strategy for using trees to improve climate and ecosystems? Go natural“. There’s some really inspiring stories in here, it’s well worth taking a look.  The main message of the article is that allowing forest vegetation to naturally regenerate, from seeds, and dormant roots and stumps, is by far the best way to ensure that trees survive and the restoration is successful.  However there’s something fundamental missing from that article: the role of species interactions in determining the survival of these forests over long time scales.

The vast majority of the world’s plants are animal pollinated; this includes trees.  Even in the UK where we often associate trees with wind pollination, about 65% of our native species are insect pollinated.  In the tropics this can rise to 100% of species within a community.  Although many of those trees can engage in some self-pollination, in the long term this is likely to result in genetic problems associated with inbreeding.  Outcrossing sex is common in plants for a good reason.

Similarly many trees require animals to move their offspring away from the parent plant.  This avoids competition between parent and offspring, and the impacts of diseases and pathogens caused by the Janzen-Connell Effect.  I don’t have any comparable statistics on the proportion of trees, regionally and globally, that use animals as seed dispersers (does anyone?  Please comment below if I’ve missed something).  But I’m willing to bet that it’s a high proportion.

Without pollinators and seed dispersers, restored forests will not flourish in the long term.  There seems to be an implicit assumption that once the forests are established, the pollinators and seed dispersers will follow.  That may be true up to a point, but it shouldn’t be taken for granted, particularly for isolated fragments of forest with no ecological connections to more established areas of woodland.  These are the aspects that are missing from John Carey’s (otherwise fine) article, and indeed from wider discussions about forest restoration and tree planting.  As so often when we talk about the conservation of biodiversity we neglect to consider the role of species interactions.  I’ve been trying to press home that point for years, on the blog and in papers, and I was pleased to see an interesting contribution to this topic by Pedro Luna and colleagues from Mexico on “Measuring and Linking the Missing Part of Biodiversity and Ecosystem Function: The Diversity of Biotic Interactions“.

Let’s not forget: species do not occur in isolation, and the biodiversity of species interactions in fundamental to the ecology of the planet.

Impact of extreme events on pollinators: download it for free

SHOCKs image

In my last post I highlighted a couple of recent papers on climate change and extreme events, and how they impact pollinators.  The Erenler et al. (2020) mini-review paper that I mentioned has now been published and is available for free download for the next 50 days.  Follow the hot link here:

Erenler, H.E., Gillman, M.P. & Ollerton, J. (2020) Impact of extreme events on pollinator assemblages.  Current Opinion in Insect Science 38: 34-39

This review is one of several from a themed issue of Current Opinion in Insect Science devoted to Ecology.  The issue is edited by Tom Ings from Anglia Ruskin University and Sarah Arnold from University of Greenwich.


Pollinators, climate change, and extreme events: two recent publications

SHOCKs image

Well, we’re back in the UK now and have just about got over the jet lag.  I’ve returned to teaching, admin, and meetings, and both Karin and I are trying to find time to finish our books.  But the persistent backdrop to our stay in Australia – the bushfires and the role of climate change, and the ensuing tensions between scientific evidence and politics – is still fresh in our minds.  It’s timely, then, to highlight two new papers that focus on extreme events, climate change and pollinators.  The first is one of my own, led by Dr Hilary Erenler who carried out her PhD research in my group.  It’s an invited mini-review in the journal Current Opinion in Insect Science entitled “Impact of extreme events on pollinator assemblages” (Erenler et al. 2020).  The review is available as a pre-print on the journal’s website; we’ve not yet even seen the proofs, though the final version should not be too different.  If you want a copy, just ask.

In this essay we focus on what we term SHOCKS: events that provide a Sudden, High-magnitude Opportunity for a Catastrophic ‘Kick’ to the environment that can negatively affect pollinator assemblages in many different ways.  Such events can be natural, human-mediated or human-enhanced, and occur suddenly, at a high-magnitude and with possibly catastrophic outcomes for those pollinators. There are many examples of such SHOCKs, as we illustrate in the figure above which comes from the paper.  However one of our main conclusions is just how little we understand about the outcomes of such events on pollinators.  Ideally we need before, during and after event monitoring to assess how pollinators have been affected and may respond.  But SHOCKs are, by their very nature, infrequent and unpredictable, and often we don’t have the baseline data with which to compare to post-event data.  I know from conversations with Australian pollination ecologists that some have had their field sites burned and they are going to use this as an opportunity to assess how the fires have impacted pollinators.  Field experiments such as the one by Biella et al. (2019) that I discussed last year, in which flowers were removed from a plant community, may also give us some insights into the response of plant-pollinator networks to sudden SHOCKs.  But we need more research focus on this topic, especially consideration of how the impacts of SHOCKs can be reduced and mitigated.

One set of emerging human-enhanced SHOCKs highlighted by Erenler et al. (2020) is extreme weather events that are being exacerbated (in scale or frequency) by anthropogenic climate change.  We cite several papers and reviews that have considered this, but there’s still few empirical studies that have actually looked at how weather SHOCKs might be impacting pollinators.  It’s therefore timely that this week’s Science includes a very impressive study of how climate change has affected populations of bumblebees (Bombus spp.) in Europe and North America (Soroye et al. 2020).

The title of the paper rather gives away its findings:  “Climate change contributes to widespread declines among bumble bees across continents“.  This study shows that, for the 66 species of Bombus studied, there had been a decline in species diversity in 100 km x 100 km quadrats of, on average, 46% in North America and 17% in Europe.  This loss of diversity has occurred in the period 2000–2014, relative to a baseline of 1901–1974.  Using some sophisticated analyses they show that climate change has been the main driver of these losses, and has been more important than factors such as changes in land use, pesticides, etc.  Which is not to discount those other contributors to pollinator loss: they can interact with climate change and are all part of the assault that we are imposing on the environment.

The most significant finding of the Soroye et al. (2020) study, and the reason why I’m discussing Erenler et al. (2020) in the same post, is that it’s extreme heat which seems to be the driving factor in determining Bombus declines.  Bumblebees are large, hairy insects because they are adapted to cooler conditions: they are not, by and large, tropical insects, except in mountainous areas.  Not surprisingly, then, it is the number of days of temperatures higher than those historically encountered by particular bee species that is the main driver of their loss from a region.  In relation to the figure above, this is the result of human-enhanced SHOCKs, and for heat-sensitive species like bumblebees, they are occurring more often than we had imagined when we wrote our review.  I fear that the coming years will see more examples of this as the effects of anthropogenic climate change continue to play out and our world experiences more extremes of weather events that are hotter, wetter, colder, drier, windier, and more combustible than we have previously known.


Biella P., Akter A., Ollerton J., Tarrant S., Janeček Š., Jersáková J. & Klecka J. (2019) Experimental loss of generalist plants reveals alterations in plant-pollinator interactions and a constrained flexibility of foraging. Scientific Reports 9: 1-13

Erenler, H.E., Gillman, M.P. & Ollerton, J. (2020) Impact of extreme events on pollinator assemblages.  Current Opinion in Insect Science (in press)

Soroye, P., Newbold, T. & Kerr, J. (2020) Climate change contributes to widespread declines among bumble bees across continents. Science 367: 685-688 [see also the commentary by Bridle and van Rensburg pp. 626-627 of the same issue]