Category Archives: Hoverflies

Garden pollinators for PAW no. 2 – Marmalade hoverfly (Episyrphus balteatus)

One of the most frequently encountered of hoverfly species in urban gardens is the beautifully named Marmalade hoverfly (Episyrphus balteatus). This insect is a “true fly” of the order Diptera that is sometimes confused with superficially similar wasps (order Hymenoptera), though (as the common name suggests) the species is translucent orange and black in colour rather than waspish yellow and black. It also has a very flat abdomen whereas wasps are rounded, and they certainly don’t sting.

Individual insects are relatively ineffective as pollinators – they are small and not very hairy, so carry little pollen compared to bumblebees for instance. However they can be extremely abundant and that abundance makes up for any individual ineffectiveness. It’s a real generalist, visiting lots of different types of flowers, and in my garden they visit radishes (as I noted last year) and raspberries.

I often see individuals patrolling crops such as runner beans, not visiting the flowers but laying eggs on leaves and stems: the larvae of the Marmalade hoverfly is carnivorous and feeds on aphids, so it plays an interesting dual role of both pollinator and pest controller. Definitely a gardener’s friend!

How can an understanding of plant–pollinator interactions contribute to global food security? A new discussion paper

29 Replies

A new discussion/review paper that I contributed to has just been published in the journal Current Opinion in Plant Biology. Entitled “How can an understanding of plant–pollinator interactions contribute to global food security?” the paper was written in collaboration with Professor Beverley Glover and her PhD students Emily Bailes and Jonathan Pattrick at the University of Cambridge.

The abstract and highlights are copied below; if anyone wants a PDF of the full paper, send me an email or ask in the comments section.

Abstract:

Pollination of crops by animals is an essential part of global food production, but evidence suggests that wild pollinator populations may be declining while a number of problems are besetting managed honey bee colonies. Animal-pollinated crops grown today, bred in an environment where pollination was less likely to limit fruit set, are often suboptimal in attracting and sustaining their pollinator populations. Research into plant–pollinator interactions is often conducted in a curiosity-driven, ecological framework, but may inform breeding and biotechnological approaches to enhance pollinator attraction and crop yield. In this article we review key topics in current plant–pollinator research that have potential roles in future crop breeding for enhanced global food security.

Highlights:

Animals are globally, and increasingly, important for the improved yield and quality of many crops.
Floral traits are a promising and little explored avenue for the improvement of crop yields.
Work surrounding plant–pollinator interactions can inform us on the best strategies to do this.
Coordinating crop flowering time with key lifecycle stages of pollinators could benefit both crop yields and pollinators.

Plantlife’s road verge advice could negatively affect pollinators

22 Replies

Did anyone else hear the item on Radio 4 this morning about Plantlife’s road verge campaign and associated petition? I listened carefully to the discussion and am broadly supportive of what they are trying to achieve. But I was immediately struck by a comment that local councils should cut the verges “from mid July onwards” because most plants will have set seed by then. I’ve seen this advice given before and whilst it might be an appropriate option for plants, it could severely impact local pollinator populations.

The printed advice that Plantlife is offering (which can be found here) states that if it’s only possible to cut a verge once a year:

“Cut the full width of the verge….between mid July and September. This allows plants to flower and, importantly, gives time for seed to be set.”

This misses a vital point: between mid-July and September there is still an abundance of flower-visiting insects that require these flowers to provide resources for their nesting and egg laying activities, or to build up reserves of energy to allow them to hibernate, particularly newly-mated queen bumblebees.

Where’s the evidence to support my assertion? It’s been demonstrated by a number of studies, but I’ll point you in the direction of a paper that came out of the PhD work of one of my former students, Dr Sam Tarrant, who now works with RSPB. If you look at Figure 4 of this paper, you’ll see that on restored landfill sites the abundance of pollinators in autumn surveys (conducted September-October) was just as high as for summer surveys. On nature reserves, which are routinely cut from mid-July onwards (see Figure 2), this was not the case.

Climate change means that flower-visiting insects are now active in the UK for a much longer period of time than was previously the case, up to at least November in the south of the country. I agree with Plantlife that road verges are important habitats for plants and other wildlife. But advice that suggests cutting floral resources at a key time of the year for these insects is simply misguided. A cut between October and December would be much more appropriate.

I don’t use Twitter so if anyone could point this at Plantlife’s account I’d be interested to see what their reaction is.

How good is the evidence base for pollinator declines? A comment on the recent Ghazoul and Goulson Science correspondence

32 Replies

In a recent issue of the journal Science, Dave Goulson and colleagues presented a review entitled “Bee declines driven by combined stress from parasites, pesticides, and lack of flowers”. This stimulated Jaboury Ghazoul to submit a letter to Science criticising the Goulson et al. paper from a number of perspectives, but particularly the paucity of the evidence base for pollinator declines. Dave and his co-authors robustly responded to that letter, as you might imagine. In some respects this was an unsatisfactory exchange, however, as the focus was largely on agricultural pollinators, rather than pollinators of all plants (including the majority non-cultivated species) and I think that (perhaps with more space?) Dave could have outlined the evidence in more depth.

The most striking statement in Jaboury’s letter was that the “evidence for pollinator declines is almost entirely confined to honeybees and bumblebees in Europe and North America”.

Now, even given the fact that Jaboury was possibly referring specifically to agricultural pollinators, that is a very extreme statement to make. Underlying it is the suggestion that global concerns about declining pollinator biodiversity (a subject I’ve discussed repeatedly on this blog) is underpinned by a taxonomically and geographically thin evidence base. Is that really true? I don’t believe so and I think it’s worth presenting a brief overview of the evidence, not least because Dave’s review and the resulting correspondence is pay-walled at the Science site (though if you Google the titles you might, just might, find copies posted on the web…)

Let me state from the outset that I have considerable respect for both Jaboury and Dave, as individuals and as scientists. I’ve known Dave since we were postgrads together in the early 1990s, and have had occasional contact with Jaboury through conferences and via email. So this isn’t meant to be a criticism of either of them. But I do believe that the evidence for pollinator declines is considerably more robust than Jaboury acknowledges, and even more wide ranging than Dave and colleagues describe in their response (though in fairness, most of the bee evidence was cited in their original review).

Here’s a summary of where I see the evidence base at the moment; it’s not meant to be a full review, by any means, but rather to give a flavour of the taxonomic and geographical breadth and depth of the evidence as it currently stands:

Wild bees (including bumblebees, and solitary and primitively eusocial bees) – significant reduction of abundance and diversity at local, regional and country-levels documented in Britain (Biesmeijer et al. 2006, Ollerton et al. 2014), Holland (Biesmeijer et al. 2006), Europe as a whole (Kosier et al. 2007, the recent IUCN Red List by Nieto et al 2014), North America (Grixti et al. 2007, Cameron et al. 2011, Burkle et al. 2013), South America (Morales et al. 2013; Schmid-Hempel et al. 2013), China and Japan (Xie et al. 2008; Williams et al. 2009; Matsumura et al. 2004; Inoue et al. 2008), and South Africa (Pauw 2007).

Honey bees – colony declines documented in Europe and North America (see reviews by NRC 2007, Potts et al. 2010) and evidence that global demand for honey bee pollination services is outstripping supply (Aizen and Harder 2009).

Hoverflies (Syrphidae) – diversity declines documented in Holland and Britain (Biesmeijer et al. 2006).

Butterflies and moths – diversity and abundance of Lepidoptera has declined in the UK (Gonzalez-Megias et al. 2008, Fox 2013), whilst in North America some 50 species are IUCN criteria Red Listed and there is particular concern about the iconic Monarch butterfly. Likewise a significant fraction of butterflies in other parts of the world are of conservation concern, e.g. Southern Africa, Australia, and Europe.

Flower-visiting wasps – reduction in country-level diversity in Britain (Ollerton et al. 2014).

Birds and mammals – the major vertebrate pollinators have recently been assessed at a global level by Regan et al. (2015) using IUCN Red List criteria. They concluded that: “overall, pollinating bird and mammal species are deteriorating in status, with more species moving toward extinction than away from it. On average, 2.5 species per year have moved one Red List category toward extinction in recent decades, representing a substantial increase in the extinction risk across this set of species”.

Of course a number of the studies cited above have shown that some species are doing better than others and a proportion of the taxa they have assessed are stable or even increasing in abundance (including managed honey bee colonies in some parts of the world). But the current evidence base, as I see it, is pointing towards significant declines in pollinator abundance and diversity at multiple spatial scales across all regions that have so-far been assessed with any rigour, for a wide range of taxa.

I’m happy to receive comments on this topic, particularly pointing me to major sources of evidence that I’ve not covered, or if you disagree with my conclusions.

References

Aizen and Harder (2009) The global stock of domesticated honeybees is growing slower than agricultural demand for pollination. Current Biology 19: 915–918.

Biesmeijer et al. (2006) Parallel declines in pollinators and insect-pollinated plants in Britain and the Netherlands. Science 313: 351–354.

Burkle et al. (2013) Plant-pollinator interactions over 120 years: Loss of species, co-occurrence, and function. Science 339, 1611–161.

Cameron et al. (2011) Patterns of widespread decline in North American bumble bees. Proc. Natl. Acad. Sci. U.S.A. 108: 662–667.

Fox (2013) The decline of moths in Great Britain: a review of possible causes. Insect Conservation and Diversity 6: 5–19.

Gonzalez-Megias, A. et al. (2008) Changes in the composition of British butterfly assemblages over two decades. Global Change Biology, 14: 1464-1474.

Grixti (2009) Decline of bumble bees (Bombus) in the North American Midwest. Biol. Conserv. 142, 75–84 (2009).

Inoue et al. (2008). Displacement of Japanese native bumblebees by the recently introduced Bombus terrestris (L.) (Hymenoptera: Apidae). J. Insect Conserv. 12: 135–146.

Kosior (2007) The decline of the bumble bees and cuckoo bees (Hymenoptera: Apidae: Bombini) of Western and Central Europe. Oryx 41, 79–88.

Matsumura et al. (2004) Invasion status and potential ecological impacts of an invasive alien bumblebee, Bombus terrestris L. (Hymenoptera: Apidae) naturalized in Southern Hokkaido, Japan. Glob. Environ. Res. 8, 51–66.

National Resource Council (2007) Status of Pollinators in North America. National Academies Press, Washington, DC.

Nieto et al. (2014) European Red List of Bees. Publication Office of the European Union.

Ollerton et al. (2014) Extinction of aculeate pollinators in Britain and the role of large-scale agricultural changes. Science 346: 1360-1362.

Pauw (2007) Collapse of a pollination web in small conservation areas. Ecology 88: 1759-1769.

Potts et al. (2010) Declines of managed honey bees and beekeepers in Europe. Journal of Apicultural Research 49: 15–22.

Regan et al. (2015) Global Trends in the Status of Bird and Mammal Pollinators. Conservation Letters DOI: 10.1111/conl.12162

Schmid-Hempel et al. (2013) The invasion of southern South America by imported bumblebees and associated parasites. Journal of Animal Ecology 83: 823–837.

Williams et al. (2009) The bumblebees of Sichuan (Hymenoptera: Apidae, Bombini). Syst. Biodivers. 7: 101–189.

Xie et al. (2008) The effect of grazing on bumblebees in the high rangelands of the eastern Tibetan Plateau of Sichuan. Journal of Insect Conservation 12: 695–703 (2008).

Pollinator seminar at Westminster – the official version – and that 1,500 figure

2 Replies

Last month I wrote a personal account of the National Pollinator Strategy Seminar held at Westminster. This week the Parliamentary Office for Science and Technology released their official summary of the event plus PDFs of the slides of some of the participants. They can be downloaded from this website. It was an interesting seminar and it’s well worth taking time to study these documents; they are very accessible for the non-specialist.

One thing that’s unclear to me from this account is with regard to the statement that: “there are approximately 1,500 insect species that pollinate food crops and wild plants, including bees, hoverflies, wasps, flies, butterflies, beetles and moths”. The National Pollinator Strategy also cites that figure, though says “at least 1,500” species.

Where does the 1,500 figure come from? Does anyone know the original citation? I genuinely can’t recall if I’ve ever seen it published.

A quick back of the envelope, conservative calculation suggests to me that 1,500 species is too low:

Aculeates (bees plus wasps minus ants) =	500
Butterflies =	59
Macro-moths (assumed 50% flower visitors) =	400
Hoverflies =	250
Other flies (assumed 10% flower visitors) =	700
Beetles (assumed 5% flower visitors) =	200
Total species =	2109

Links are included to the sources of the original diversity figures. I’ve rounded some of the figures down and the % flowers visitors figures for moths, flies and beetles is pure guestimate based on my field experience. But they are not likely to be way out, and if anything could be an under-estimate for flies and beetles; moths could be too high, though most species do feed as adults. Aculeate Hymenoptera (bees and wasps) could also be an over-estimate, but then that figure doesn’t include the non-aculeate “wasps” that frequently visit flowers, for example many ichneumonids and sawflies.

Does it matter? I think so: as scientists it’s important that we provide the most accurate data that we can to governments and other bodies that may use it for policy, strategy and advocacy.

As always I’d be pleased to receive your comments.

Urban pollinators for urban agriculture (and horticulture!)

9 Replies

Over the past few weeks I’ve been thinking a lot about urban pollinators, that is to say bees, hoverflies, butterflies, and other animals, living and foraging in towns and cities. As I recounted in my recent post about the National Pollinator Strategy seminar at Westminster, Jane Memmott presented some of the first data from the Urban Pollinators Initiative which is looking very interesting. At the same time, Muzafar Hussain has submitted the first manuscript from his PhD study of urban solitary bees in Northampton, and will hopefully be defending his thesis early next year. More recently I was asked to examine the PhD thesis of Rob Fowler at the University of Birmingham, whose focus has been on pollinators across an urban-rural gradient. Rob did very well and I look forward to seeing his work published.

Interesting though all this work is, it’s largely being done outside the context of crop pollination per se, focusing mainly on the identity and abundance of these urban pollinators. It’s timely, therefore that a study has just been published by Thebo et al. in the journal Environmental Research Letters entitled “Global assessment of urban and peri-urban agriculture: irrigated and rainfed croplands” which gives the first comprehensive figures on the extent of agriculture in and around the world’s large towns and cities. The paper is open-access so you can read its findings for yourself, but the main message is that urban agriculture is more extensive and important than previously assumed, and there are significant implications for food security and water resources.

The research has (justifiably) received quite a lot of publicity in the media, for example on the BBC News website, and is a great contribution to a still limited field of study. One aspect jumped out at me though; when discussing the limitations of their methods the authors state that: “the scale and methods used……are not structured to capture very small, spatially dispersed areas of urban croplands”. In other words, urban gardens and allotments are not included in this assessment. In the UK at least this is a significant limitation as we know that urban fruit and vegetable growing is widespread, though as far as I’m aware there’s no published figures on the volume and value of this local horticulture of food crops.

Which brings us back to urban pollinators: a significant fraction of these crops (large-scale and local garden) requires pollination by insects. As I reported back in July, in our own urban garden this includes at least 15 crops (strawberries, apples, greengages, cherries, blackcurrants, squashes, courgettes, blackberries, fennel, runner beans, french beans, passion fruit, tomatoes, raspberries, and radish pods). An integrated study of urban agriculture/horticulture in the context of pollinator diversity and abundance would be a great piece of research and is long overdue.

The National Pollinator Strategy – some reflections

14 Replies

After many months of consultation and workshops, the National Pollinator Strategy for England has finally been released by Defra, and can be downloaded from this website. It reflects an important, wider change in societal attitudes to nature, and specifically the ecosystem services it provides, though the strategy itself is by no means perfect. I rather wish that it had been a UK-wide strategy, as biodiversity does not respect political boundaries, but such is a the nature of our partly-devolved political system. Wales already has an Action Plan for Pollinators and I hope that the rest of the UK follows, though a strategy for Northern Ireland would surely have to include the Republic of Ireland?

In the following sections I’ve quoted liberally from the summary section of the National Pollinator Strategy, and added a few comments and reflections of my own in italics. As always, your views and comments would be very welcome.

The 10 year National Pollinator Strategy aims to deliver across five key areas:

1. Supporting pollinators on farmland

Working with farmers to support pollinators through the Common Agricultural Policy and with voluntary initiatives to provide food, shelter and nesting sites.
Minimising the risks for pollinators associated with the use of pesticides through best practice, including Integrated Pest Management (IPM).

Comment: at the moment many farmers are already pro-actively encouraging pollinators and other wildlife, but most are not. Will “voluntary initiatives“, including encouraging Integrated Pest Management, be sufficient? About 70% of the country is farmed and any wildlife conservation strategy has got to include agricultural stakeholders. But the influence of large agro-chemical businesses should not be under-estimated. I’ve seen figures suggesting that fields of oil seed rape in this country receive applications of up to 20 different chemicals (biocides and fertilisers) each year. That represents a significant profit for these companies, who will not want to change the status quo. Data showing a slow down in the rate of decline of plants and pollinators in Great Britain, the Netherlands and Belgium may be evidence that CAP agri-environmental schemes have had a positive impact, but I’d like to see more data addressing that question (and not just for pollinators – farmland birds are doing worse than any other category of birds in the UK).

2. Supporting pollinators across towns, cities and the countryside

Working with large-scale landowners, and their advisers, contractors and facility managers, to promote simple changes to land management to provide food, shelter and nest sites.
Ensuring good practice to help pollinators through initiatives with a wide range of organisations and professional networks including managers of public and amenity spaces, utility and transport companies, brownfield site managers, local authorities, developers and planners
Encouraging the public to take action in their gardens, allotments, window boxes and balconies to make them pollinator-friendly or through other opportunities such as community gardening and volunteering on nature reserves.

Comment: “simple changes to land management” can do a lot for supporting local biodiversity, even in the most unlikely, urban settings, which is the underlying philosophy behind our award-winning Biodiversity Index tool. Quite a number of local authorities are getting the message that it’s A Good Thing to reduce the frequency of cutting amenity grasslands, both for pollinators and for budgets. But local authorities are also taking foolish decisions with regard to developing sites that should be protected, and brownfield areas are being specifically targeted for building urban housing, despite the fact that we have long known that they are some of our best sites for pollinators. How do we reconcile these different priorities? Brownfield sites by their nature are transitory, early successional habitats, so perhaps local authorities should be encouraged (made?) to have a rolling stock of a minimum proportion of undeveloped brownfield sites as part of their portfolio of land holdings? Or how about a requirement that all developed areas of brownfield land are replaced by an equivalent area of brown roofs?

3. Enhancing the response to pest and disease risks

Working to address pest and disease risks to honey bees whilst further improving beekeepers’ husbandry and management practices to strengthen the resilience of bee colonies.
Keeping under active review any evidence of pest and disease risks associated with commercially produced pollinators used for high-value crop production.

Comment: interestingly there’s no mention of disease risks to non-managed pollinators, yet we know that honey bee diseases can be passed to bumblebees, for instance.

Actions to support these priority areas:

4. Raising awareness of what pollinators need to survive and thrive

Developing and disseminating further advice to a wide range of land owners, managers and gardeners as part of Bees’ Needs.
Improving the sharing of knowledge and evidence between scientists, conservation practitioners and non-government organisations (NGOs) to ensure that actions taken to support pollinators are based on up-to-date evidence.

Comment: yes, dissemination of sound, evidence-based knowledge has got to be a priority.

5. Improving evidence on the status of pollinators and the service they provide

Developing a sustainable long-term monitoring programme so we better understand their status, the causes of any declines and where our actions will have most effect.
Improving our understanding of the value and benefits pollinators provide, and how resilient natural and agricultural systems are to changes in their populations.

Comment: monitoring of pollinators is a real sticking point in the strategy, as there’s still no consensus on what should be monitored, how, where, and how frequently. This was the subject of a workshop at the Natural History Museum in London that I attended about a year ago, and there’s still much that is undecided. I know that a partnership led by CEH Wallingford is working on this at the moment, and hopefully a scheme will be in place by next year. Let’s see what they come up with.

In taking action across these five areas, the National Pollinator Strategy wants to achieve the following outcomes:

More, bigger, better, joined-up, diverse and high-quality flower-rich habitats (including nesting places and shelter) supporting our pollinators across the country.
Healthy bees and other pollinators which are more resilient to climate change and severe weather events.
No further extinctions of known threatened pollinator species.
Enhanced awareness across a wide range of businesses, other organisations and the public of the essential needs of pollinators.
Evidence of actions taken to support pollinators.

Comment: “More, bigger, better, joined up…” has been the buzz phrase in British conservation since at least the Lawton Report. One of the outcomes of that report was the setting up of twelve flagship Nature Improvement Areas (NIAs), one of which is the Nene Valley NIA, a project on which my research group has been working. The Strategy mentions the NIAs several times and states that “extending the monitoring and evaluation framework for Nature Improvement Areas to include pollinators” is one of its interim aims. But as I recently mentioned, funding for the NIAs finishes at the end of March 2015 and Defra has indicated that there will be no additional government money. How will this aim be met? I’d be very interested to know as the Nene Valley NIA is one of the few which specifically focused on pollinators as part of our remit. It would be a terrible shame to lose the expertise and momentum that we’ve built up when funding stops next year. As regards “No further extinctions of known threatened pollinator species“, the talk I gave at SCAPE 2014 was on that very topic and a paper outlining our results is currently in press. I hope to be able to share those findings with the broad readership of this blog very shortly.

A Westminster pollinator seminar and The Great British Big Bee Count

12 Replies

In the run up to Defra’s publication of a National Pollinator Strategy, due for release some time before Christmas, the Parliamentary Office for Science & Technology yesterday ran a two hour seminar at Westminster. It was a full meeting in one of the small rooms, and apparently over-subscribed which doesn’t surprise me: there’s huge interest in pollinator conservation in the UK at the moment. So it would have been better moved to a larger room to allow more scientists, practitioners, MPs, civil servants and other interested parties to attend. In any case it was a useful couple of hours, with some interesting updates on what’s happening in relation to British pollinators.

The event was chaired by Sarah Newton MP and was kicked off by Adam Vanbergen from the Centre for Ecology and Hydrology who got everyone up to speed by giving an overview of the science of pollination, pollinator diversity, and the issues affecting pollinator populations. In the process he cited our “How many flowering plants are animal pollinated?” paper which has fast become the default citation to use as evidence to support the ecological importance of biotic pollen transfer. That’s hugely gratifying and is what it was designed to do. We now have additional data with wider geographical coverage and I hope to update that analysis in the near future. A lot of the information Adam was using can be found on the Insect Pollinators Initiative website.

Adam’s talk was followed by a presentation by Simon Potts from the University of Reading who discussed how we value pollination as an ecosystem service and how we can safeguard pollinator abundance and diversity. There were some stark statistics on the economic contribution of pollinators to crops such as apples, including data from a study by Garratt et al. (2014) which suggests that both quality and quantity of apples could be improved by having more pollinators in British orchards. Perhaps another way of viewing those data is that the UK apple industry is already experiencing the kind of pollinator deficit that conservationists have predicted?

Jane Memmott from Bristol University was next, presenting the preliminary results of the Urban Pollinators Initiative which is the first comprehensive study of the distribution of pollinators in large British cities. The data look really exciting and it will be great to see the results finally published as it will make for an interesting comparison with Muzafar’s data on solitary bees in Northampton, the first manuscript from which has recently been submitted to a journal.

Finally Chris Connolly from Dundee University talked about pesticides in a presentation entitled “Why pick on the neonicotinoids?” and provided some disturbing statistics on how little we really know about what happens when the c. 350 types of pesticides (plus about 700 herbicides and fungicides) that we use in modern British agriculture combine in the environment to produce synergistic effects. It’s also worrying that there is little understanding of the amounts of pesticides being applied because systematic data are not collated. Chris is a neuroscientist working mainly in a medical context and gave the analogy of how combinations of therapeutic drugs can have unforeseen (even deadly) side effects. Chris also used an image of Nigel Farage to illustrate a point which was a brave thing to do in the Houses of Parliament in the current political climate, but which got him a big laugh.

There followed 30 minutes of questions and discussion, and I managed to get in a plug for the Biodiversity Index when making a point of how difficult it is to get business to engage with biodiversity. That led to an interesting conversation afterwards with a consultant that I need to follow up later today.

Out into the unseasonably warm London air by about 6.30pm, there were people standing outside pubs and sitting at cafe tables, as if we were in southern Europe rather than England in late October. It reinforced some of the things I discussed in a post earlier this summer about climate change and current weather patterns.

Coincidentally (or not) Friends of the Earth released the results of their Great British Bee Count, a Citizen Science project designed to augment the monitoring work being done by specialist groups such as the Bees, Ants and Wasps Recording Society (BWARS). I have mixed feelings about the Great British Bee Count. On the one hand it’s great to engage the public in campaigns that raise the awareness of the importance of pollinators, and to get them out looking at bees. But the reality is that the 832,110 records submitted to the count have very limited scientific value, despite what Friends of the Earth might claim. That’s because it is very, very difficult to identify bees to even broad groups unless you’ve had some training, and (apart from some distinctive species) impossible to identify to species level unless you are a specialist. I’ve been studying pollinators for 25 years and there are whole groups within our c. 250 native species that I have great problems identifying, and defer to the opinion of real specialists such as Stuart Roberts, chair of BWARS.

Stuart has made public his concerns at the quality of the data being submitted to the Great British Bee Count, and the fact that records cannot be checked because no photograph was taken and (worse) there are no specimens to compare. The issues are neatly embodied in the fact that four species which were recorded from Northern Ireland (Tawny mining bee, Hairy-footed flower bee, Red mason bee, and Tree bumblebee) have never previously been seen in Ireland and can all be confused with other similar species. Of particular concern is the fact that Friends of the Earth expects the National Biodiversity Network Gateway to archive the data. If that happens the Great British Bee Count data MUST be kept separate from the high quality, verified data on bee distributions that NBN already possesses, otherwise it will completely devalue the latter. By all means let’s get the public engaged with pollinators and biodiversity more broadly, which is one of the purposes of this blog after all! But let’s also be realistic about what can be achieved by these kinds of campaigns.

All pollinators are equal, but some pollinators are more equal than others

8 Replies

The infamous line from George Orwell’s Animal Farm asserting that “All animals are equal, but some animals are more equal than others” nicely captures an ecological view of pollinators and their relationships with plants. “Pollinators” by definition move pollen between flowers, but not all pollinators are equally good at transferring pollen of any particular plant: some are more effective than others. I’ll illustrate this with examples from the urban garden that Karin and I are developing, which I’ve discussed before.

As you can see from that link, the garden is modest in size, but nonetheless this year it contains a significant biodiversity of edible plants that require pollinators for some or all of the fruit and seed set, including: strawberries, apples, greengages, cherries, blackcurrants, squashes, courgettes, blackberries, fennel, runner beans, french beans, passion fruit, tomatoes, raspberries, and radishes.

“Radishes?!” I hear you ask. “But they are grown for their edible swollen roots which don’t require pollination!” True, usually. But we let our radishes flower because we mainly grow them for their seed pods which, picked young, are delicious in salads and stir fries, like mustardy mange tout. They look like this:

The radish flowers are pollinated by a diversity of insects including butterflies, bees, and small flies:

These insects will vary in their effectiveness as pollinators of radish, depending on the frequency of visits, how often they move between flowers, and the amount of pollen on their bodies. This last factor is largely a function of size and hairiness (bigger, hairier insects carry more pollen as a rule), though cleanliness also plays a part: insects often groom the pollen from their bodies and, in the case of bees, may pack it into their pollen baskets where it’s not available for pollination.

The size and behaviour aspect is best illustrated by some recent photos that I took of visitors to the flowers of passion fruit (Passiflora caerulea var.). We have a large, sprawling plant growing up a fence which is currently being visited by honey bees, hoverflies, solitary bees and bumblebees. In comparison to the size of the flower and the position of the anthers (male, pollen producing parts) and stigmas (female, pollen receiving parts), the hoverflies, honey bees and solitary bees are relatively small. These two images are of honey bees (Apis mellifera):

Here’s an unidentified solitary bee:

These bees were occasionally touching the anthers, mainly with their wings, so some pollen will be moved around. But from what I observed it’s likely to be a relatively small amount in comparison to bumblebees, which are usually much larger and hairier, and don’t groom themselves as often as honey bees. Here’s a Buff-tailed bumblebee (Bombus terrestris):

They were actively collecting pollen as well as nectar. Much of this pollen is packed into the pollen baskets on the rear legs and will go back to the nest to feed the developing larvae, but some will be involved in pollination:

So it seems to be the bumblebees we have to mainly thank for the deliciously sweet-sour fruit we will enjoy later in the season. Of course to test this properly we would need to set up an experiment in which we excluded larger bumblebees from the flowers and only allowed smaller bees to forage, with appropriate experimental controls. Would make a great project if any of my students are interested! But it should give you a sense of just how complex the interactions between flowers and their pollinators are: the ecology of pollination is far from simple, despite what some would have us believe.

Thank the insects for Christmas (REBLOG)

9 Replies

It’s become a tradition (ok, only for the past two years, but a tradition has to start somewhere!) for me to post a version of this festive blog entry. I’ve updated the stats for 2013. Hope you enjoy it.

Christmas! A time to relax and enjoy ourselves, to share time with family and friends, and to unwind during the cold and gloom of winter. Whatever your faith, or lack of it, Christmas should be about taking a break and reflecting on the year that has passed. We’re helped in that respect by the ceremonial seasonal trimmings: the Christmas tree, strings of flashing lights, baubles and tinsel. So while you’re kissing a loved one under the mistletoe, admiring that glossy holly wreath, or tucking into your Christmas dinner, spare a thought for the insects.

“What in Saint Nicholas’s name” you are asking ”have insects got to do with Christmas?!” Well, like the turkey, we’d be stuffed without them: they play an essential part in providing us with the things we associate with Christmas. If we had no flies, wasps, bees and other bugs acting as pollinators there’d be no berries on your mistletoe or your holly. Kissing and admiring would be a less festive affair and that’s just for starters. These insects also pollinate many of the vegetables, herbs and spices on your plate, as well as some of the forage that went to fatten your roast bird or tender joint of meat. Not to forget much of what went into the nut roast that’s feeding the vegetarian relatives.

The economic value of insect pollination in the UK was estimated by the recent National Ecosystem Assessment to be about £430 million per year. In fact this is a huge under valuation because the labour costs alone of paying people to hand pollinate those crops would run into billions of pounds. This sounds far fetched but it’s already happening to fruit crops in parts of China. The answer is to encourage wild insects, not artificially managed honey bees, because collectively the former are far more abundant, and often more effective, as pollinators. Their diversity is an insurance against losing any one species in the future. The NEA’s valuation is also too low because it only deals with commercial edible crops, and does not include those we grow in our gardens and allotments. It also does not take account of ornamental crops such as mistletoe and holly, both of which are dioecious species, which is to say that individuals are either male or female, rather than hermaphrodite as are most plants. This means that the plants cannot self pollinate and insects are absolutely vital to their reproduction and to the production of the decorative berries we so value (a holly wreath without berries is just a big spiky doughnut, in my opinion).

Whilst researching the economic value of the annual mistletoe and holly crops for this blog posting last year I had a conversation with Jonathan Briggs over at Mistletoe Matters and he told me that “the mistletoe trade in Britain is entirely unregulated and not documented in any tangible way”, and the same is true of holly. We therefore have no idea what the economic value of these non-food crops actually is. But some back-of-the-red-and-gold-Christmas-lunch-napkin calculations can at least give us an insight. Auction reports for 2013 show that on average the best quality berried holly was selling for £2.50 per kg whilst equivalent quality holly without berries sold for only 80p per kg. In other words, pollination by insects increases the value of that crop by more than 300%! Similarly the high quality mistletoe averaged £1.20 per kg, whilst the second grade stuff was only 40p per kg. And the best holly wreaths (presumably with berries!) were averaging £7.00 each.

These are wholesale prices, of course; retail cost to the customer is much greater. A decent holly wreath will set you back between £15 and £30 whilst online shopping for mistletoe is in the £5 to £20 range, depending on how much you want. The national census of 2011 shows us that there are 23.4 million households in England and Wales, plus there are 2.36 million in Scotland and 0.70 million in Northern Ireland. Let’s round it down and say there’s 26 million households in the whole of the UK. Let’s also be very conservative and estimate that only 5% of those households bought one holly wreath and some mistletoe at a total cost of £20. Multiply that by the small proportion of households buying these festive crops and you arrive at a figure of about £26.5 million! And that doesn’t include non-household use in shops, offices and businesses. So there you have it: an industry worth a few tens of millions (at least) all being ultimately supported by insects.

With pollination, timing is everything, and Jonathan also made the point that spring flowering mistletoe and holly can be important early nectar sources for insects. Therefore despite the poor summer weather in 2012, that year was a good one for mistletoe berries because the pollination happened before the heavy rains began. Despite being quite common plants, rather little research has been done on either holly or mistletoe pollination in the UK and it would make for an interesting student project. The Landscape and Biodiversity Research Group here at the University has for many years been working to understand the ecology of plants and pollinators, and how to best conserve them. In this blog I’ve referred a few times to some ongoing projects researching how the wider landscape is supporting pollinators in habitats such as country house gardens (Hilary Erenler’s PhD work which she completed this year) and urban centres (ongoing PhD work by Muzafar Hussain). There’s also the work completed a few years ago by Sam Tarrant and Lutfor Rahman on pollinator (and other) biodiversity on restored landfill sites. Plus research that’s recently started by Kat Harrold on how whole landscapes support pollinators in the Nene Valley Nature Improvement Area. This is all part of a broader programme of research into the conservation of biodiversity in our region and beyond, including our Biodiversity Index, a contribution to the Shared Enterprise Empowering Delivery (SEED) sustainability project.

Biodiversity matters and its importance to our society is being increasingly recognised by government, business and the public. So if you make one New Year’s resolution on the 31st December, let it be that you will put away your garden bug sprays for 2014 and learn to love the insects (even wasps!) who give us so much and help to support our economy in a very real way. It costs us nothing; all we need to give them is well managed, diverse, unpolluted habitats in which to live. Have a great Christmas everyone!