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]

14 thoughts on “Pollinators, climate change, and extreme events: two recent publications

  1. Stuart Roberts

    Not a single European co-author on the Soroye paper despite the majority of Bombus records used in the analysis coming from European datasets provided by European bombologists, Hmmmmm

      1. Stuart Roberts

        Clearly a big mea culpa here Jeff… and an apology…. I’m afraid don’t know Tim and I am unaware of his involvement in the study of Bombus on the continent. What I meant was that none of the data providers from Europe is included… and several major European climate/Bombus works not cited eg Rasmont et al (2015) Climatic Risk and Distribution Atlas of European Bumblebees. Pensoft Publishers, Sofia., ISBN: 978-954-642-769-4 (e-book), 978-954-642-768-7 (hardback). Biorisk, 10: 1-246.

      2. jeffollerton Post author

        Yeah, I think the inclusion of data providers is a different issue and I of course agree, it would have been good to have representatives from those providers as co-authors. I know from experience that Science is very restrictive when it comes to how many references can be included.

      3. Stuart Roberts

        I absolutely agree. Without Data providers there would be no data to analyse and papers such as this would not be possible. They can often (and should) provide an ecological perspective to check that things that make statistical sense also make ecological sense. The key European data providers were all co-authors (or were asked if they wanted to be co-authors) on Kerr et al (2105). I am checking to find out if they were consulted or asked about reusing the data originally submitted for the 2015 paper. BWARS, a contributor of some 12% of the European data used in 2015 was not approached and when we allow data to be used (our default position) we like to know for our own records, to be properly acknowledged, and to ensure the most up-to-date version of the dataset is used

    1. Peter Soroye

      Hi Stuart, happy to clear this up. We cite many papers done by the fantastic climate/Bombus groups in Europe. We take special care to make it very clear in the Supplemental Materials and Acknowledgements that much of our European data was collected by these groups, and we do cite the specific paper you mention, along with others including Polce et al 2018, and Potts et al 2011). As Prof Ollerton mentions, Science is extremely restrictive with how many references can be included in the main text, so these references had to be placed in the Supplemental. Myself and my co-authors are acutely aware of how critical data providers are to the work we do, and we always do our absolute best to acknowledge and thank them properly. This is why we were so happy to have you agree to our use of the data at the very beginning of this project in Sept 2017, under the condition of proper acknowledgement and citation, as we have done, and as we also agreed on with Professors Rasmont, Potts, and Schweiger. Very happy to chat about this more over email, I could have very quickly cleared up your concerns when I sent you a copy of the paper yesterday if you had mentioned them then. Best, -Peter

  2. Peter Cuthbert

    Bumblebees breeding colonies were seen in Maynooth area during November and December 2019,foraging on Mahonia
    Already Queens in my garden on early flowering Salix aegyptica, other Willows budding far to early .

      1. Helen

        Yes, it does seem a bit far-fetched. I guess the suggestion might have been part of a bigger whole that I didn’t hear or a way of saying something which is achievable/tangible for the average person.

  3. Dr P A Azeez

    Please share a PDF of the paper “Impact of extreme events on pollinator assemblages” when it is out. I have seen the other paper (Soroye et al). Thanks


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