Insects are declining – but talk of “insectageddon” is premature

I originally posted this blog on the Nature Ecology & Evolution community forum; you can read the original version here.

Recent research showing severe declines in biomass of flying insects has been much-discussed in the literature and the global media. In a new study of a long-term insect population dataset, we found that the biomass of moths increased before it declined, and remains higher now than in the 1960s.

Insects play a number of vital roles in our ecosystems, and as a consequence, several studies in recent years that have reported sharp declines in their “biomass” (combined weight) have been greeted with alarm by the media and public.

However, the conclusions of these papers have been met with scepticism by the scientific community. There is a widely-held opinion that studies on insect biomass have so far been based on too little data to be certain of their conclusions, variously having too few separate sampling sites, data from too short a time period, or from only the beginning and end of a sequence (rather than continuous data), or data collected with a non-standardized method over time.

To try and understand patterns in insect biomass change over time in a more robust way, overcoming some of these criticisms, my colleagues and I turned to the long-running network of moth-traps of the Rothamsted Insect Survey (RIS). Rothamsted currently operate around 80 identical moth-traps across the UK and Ireland, each of which collects moths (which are then identified and counted) on a nightly basis using a standardized methodology. From among these, we identified 34 traps that had operated continuously for at least 30 years in the 51-year period since the trap network commenced in 1967.

Peppered Moth (Biston betularia) has declined in abundance by 81% since 1967, according to the Rothamsted Insect Survey’s data.

To translate the abundance records collected by the RIS into estimates of biomass, we first needed to know how much each moth weighed. Rothamsted don’t retain every moth they capture, and catching and weighing a representative sample of every species in their database would be prohibitively labour-intensive. Existing dry body mass data weren’t available for most British moth species either, but field guides do list typical forewing lengths for every species as an identification tool, so we resolved to model the relationship between these two variables.

Thanks to the hard work of summer project student Becci Kinsella, we collected an empirical dataset on the forewing length and body mass of 600 individual moths from 94 species and, fitting a model to this data, estimated the body mass of over 1000 species of larger moths. Amazingly, we found this allowed us to predict around 90% of the total variation in the biomass of mixed-species samples of moths.

Next, Masters student Jonny Williams applied these estimates to data from the 34 long-running traps from the RIS, generating annual estimates of moth biomass from each trap. The results were astonishing. We found that the average biomass of moths sampled annually by each trap had approximately doubled over the 50-year duration of our dataset. This was not a simple increasing trend, either: biomass had increased steeply between 1967 and 1982, but gradually declined thereafter. The 10% per decade rate of these more recent declines actually matches up well to the findings of other recent studies of insect abundance and biomass (none of which commenced earlier than 1976), but the overall longer-term pattern of steep increase, then gradual decline does not support the widely-suggested scenario of “insect Armageddon”.

Abundance of the Large Emerald (Geometra papilionaria) reached a peak in 1983, matching the trend for moth biomass as a whole.

To understand drivers of these recent declines, we turned our attention to land-use, categorising sites into four groups: arable, grassland, woodland and urban. Two drivers of environmental change that are often mooted as potential causes of insect decline, especially for moths, are agricultural intensification (most relevant in arable sites) and light pollution (most relevant in urban sites); but we found that the steepest post-1982 biomass declines were in grassland and woodland.

The third of the “usual suspects” is climate change. A strong degree of synchronisation in both year-to-year biomass change and longer-term trends between sites, land-use types, and taxonomic groups of moths, pointed the finger of blame squarely towards factors that operate across all land-use types, such as temperature and rainfall. Yet surprisingly, we found no relationship between either of these variables and biomass change. However, two of the biggest periods of biomass change – a strong increase in the late 1970s and a decline in the late 1990s – directly followed the heatwave/drought years of 1976 and 1996. It seems possible, therefore, that extreme climatic events can perturb populations and communities, with resultant ecosystem feedbacks causing subsequent biomass change – an avenue for further research, perhaps.

Finally, we resampled the full RIS dataset to investigate the influence of data structure on estimates of insect biomass change, taking every possible subset of data of over 5 years’ duration, both for single study sites and the full 34 sites combined. It’s well-known that insect populations can fluctuate wildly from year to year, so unsurprisingly, longer spans of data were less likely to estimate massive increases or declines. Likewise, biomass changes were larger at single study sites than across the full dataset of 34 sites. Many studies rely on single return visits to previously-sampled locations, generating an estimate of biomass change between two points in time. Unfortunately, when compared to the trend fitted by a linear model through annual estimates over the same time periods, we found the two-sample approach incorrectly estimates the direction of biomass change in a quarter of cases. Lastly, it’s unwise to hang your hat on biomass change since an arbitrary start date, since patterns change over time: within our study, biomass increased since 1967, decreased since 1982, but has been roughly stable since 1997.

These findings emphasize the vital importance of long-term, standardized data collection for understanding population change. Several UK initiatives, like the RIS and the UK Butterfly Monitoring Scheme, have been doing this for decades on home soil, but globally very few such datasets exist, particularly in the tropics. Establishing long-term monitoring at a much broader scale is a challenging prospect, but a worthy goal.

Climate change is forcing butterflies and moths to adapt – but some species can’t

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The silver-studded blue butterfly is among that species that may be flexible enough to thrive.
Callum Macgregor, Author provided

Callum Macgregor, University of York

Butterflies are rather like Goldilocks, preferring conditions to be neither too hot nor too cold, but “just right”. Under climate change, the temperature at any given time of summer is, on average, getting warmer, leaving butterflies (and their nocturnal cousins, the moths) with the challenge of how to remain in their optimal temperature window.

One of the main ways in which species are achieving this is by changing the time of year at which they are active. Scientists refer to the timing of such lifecycle events as “phenology”, so when an animal or plant starts to do things earlier in the year it is said to be “advancing its phenology”.

These advances have been observed already in a wide range of butterflies and moths – indeed, most species are advancing their phenology to some extent. In Britain, as the average spring temperature has increased by roughly 0.5°C over the past 20 years, species have advanced by between three days and a week on average, to keep track of cooler temperatures.

Is this a sign that butterflies and moths are well equipped to cope with climate change, and readily adjust to new temperatures? Or are these populations under stress, being dragged along unwillingly by unnaturally fast changes?

In a new study published in Nature Communications, colleagues and I sought to answer this question. We first pulled together data from millions of records submitted by butterfly and moth enthusiasts to one of four recording schemes run by charities or research institutes. This gave us information on 130 species of butterflies and moths in Great Britain every year for a 20-year period between 1995 and 2014. We could then estimate the abundance and distribution of each species across this time, along with how far north they had moved. The data also, crucially, allowed us to estimate subtle changes in what time of the year each species was emerging from the chrysalis as a fully-grown butterfly.

It pays to reproduce quickly

Analysing the trends in each variable, we discovered that species with more flexible lifecycles were more likely to be able to benefit from an earlier emergence driven by climate change. Some species are able to go from caterpillar to butterfly twice or more per year, so that the individual butterflies you see flying in the spring are the grandchildren or great-grandchildren of the individuals seen a year previously.

Among these species, we observed that those which have been advancing their phenology the most over the 20-year study period also had the most positive trends in abundance, distribution and northwards extent. For these species – such as Britain’s tiniest butterfly, the dainty small blue – emerging early in spring gives more time for their later-summer generations to complete their reproductive cycles before the arrival of autumn, allowing more population growth to occur.

Small blue: Britain’s tiniest butterfly.
Callum Macgregor, Author provided

Other species, however, are less flexible and restricted to a single reproductive cycle per year. For these species, we found no evidence of any benefit to emerging earlier. Indeed, worryingly, we found that the species in this group that specialise in one very specific habitat type (often related to the caterpillar’s preferred diet) actually tended to most harmed by advancing phenology.

The beautiful high brown fritillary, often described as Britain’s most endangered butterfly, fits this category perfectly. It is found only alongside the dog-violets that its caterpillar eats, in coppiced woodland and limestone pavement habitats. It’s also a single-generation butterfly that has advanced its phenology. This suggests that climate change, while undoubtedly not the sole cause, might have played a part in the downfall of this species.

The high brown fritillary was once widespread, but is now found in just a few sites in Lancashire and the south-west.
Callum Macgregor, Author provided

All is not lost, however. Many of Britain’s single-generation species show the capacity, in continental Europe, to add a second generation in years that are sufficiently warm. Therefore, as the climate continues to warm, species like the silver-studded blue might be able to switch to multiple generations in the UK as well, and thereby begin to extract benefits from the additional warmth, potentially leading to population increases.

Specialists are at risk

More immediately, we can arm ourselves with this knowledge to spot the warning signs of species that may be most at risk. Clearly the single-generation habitat specialists are of particular concern, as many are already endangered or vulnerable – not just the high brown fritillary and silver-studded blue, but also species such as pearl-bordered fritillary, grizzled skipper and the particularly sought-after white admiral of southern England. Multi-generation species that are failing to advance their phenology might also be threatened: into this category falls another of Britain’s most sharply-declining butterflies: the wall brown.

Using this knowledge to help protect moths and butterflies from climate change is not simply important for the sake of the butterflies and moths themselves – these species also play a number of important roles in our ecosystems. Their caterpillars consume vast quantities of plant material, and in turn act as prey for birds, bats, and other small mammals, while moths even act as pollinators of a surprisingly wide range of plant species, possibly including some important crops.

According to Butterfly Conservation, around two-thirds of butterfly species have declined in the UK over the past 40 years. If this trend continues, it might have unpredictable knock-on effects for other species in the ecosystem. Only by arming ourselves with an understanding of why butterfly numbers are down can we hope to halt or reverse the decline.

Callum Macgregor, Postdoctoral Research Associate, University of York

The Conversation

Pollinators: switch street lights off at midnight to help moths and nocturnal wildlife

This article is republished from The Conversation under a Creative Commons license. Read the original article.

File 20190121 100261 js5ch1.jpg?ixlib=rb 1.1

Jazzi/Shutterstock

Callum Macgregor, University of York

Conservation is often a conflict between the demands of development and a desire to do what is best for the environment. It’s rare that we get the chance to report a decision which was taken for the good of people that has also panned out well for nature’s ecosystems. However, that is just what our new research paper found.

Saving energy from street lighting is not just a green option, it also makes good financial sense. Two solutions in particular include replacing old High-Pressure Sodium (HPS) lightbulbs with new and energy-efficient Light-Emitting Diodes (LEDs) and turning the lights out entirely during the latter part of the night when fewer people are around. In the UK, these changes in lighting technology have been gradually taking effect over the last decade or so.

While these decisions were made for good reasons, we knew little about how they would influence nocturnal wildlife. Our team of experts at York and Newcastle universities were interested in finding out how moths might be affected by the switchoff and new LED lighting, as they play an important role as night-time pollinators of a wide range of flowers, and have declined in abundance by 40% in 40 years.

Moths are important pollinators but have endured significant population declines in recent years.
Safwan Abd Rahman/Shutterstock

Light pollution, from street lights and other sources, has been suggested as a possible cause of this decline, though there are other factors such as climate change and habitat loss.

Our previous research showed that under HPS street lighting left on all night, moths were distracted from visiting flowers and instead flew higher up, around street lights. This resulted in less pollen being carried by moths in lit areas, and a subsequent study by Swiss researchers demonstrated that this actually caused reduced fruit production.




Read more:
Fatal attraction: how street lights prevent moths from pollinating


In our study, we asked whether the disruption to nocturnal ecosystems from street lights might be eased or exacerbated by the introduction of new energy-efficient LED street lighting. Working on farmland in East Yorkshire in the UK, we set up a chain of mock street lights alongside hedgerows that would allow us to manipulate the type and duration of lighting.

Older and less energy-efficient HPS lighting near wildflowers.
Callum Macgregor, Author provided

We compared older HPS lights to LEDS, and standard full-night lighting to part-night lighting, in which lights were turned off at midnight. All lighting was compared to an unlit control that replicated natural darkness. Under each lit and unlit treatment we placed several plants of White Campion (Silene latifolia), a common wildflower known to be pollinated by both bees and moths. We left each plant in the field for four days and nights before measuring what proportion of flowers had been pollinated, and the weight and number of seeds in every fruit.

LEDs are rich in blue light which is attractive to moths but we found no difference in the rate of pollination between plants under LEDs and those under HPS lights. Our data did show that the differences between pollination under full-night lighting and in natural darkness were erased when lights were turned off at midnight.

Newer and more energy-efficient LED lighting near wildflowers.
Callum Macgregor, Author provided

Surprisingly, this wasn’t just a partial improvement. We found no significant difference between rates of pollination in part-night lighting treatments and in natural darkness, and this suggests that turning lights off at or after midnight may allow nocturnal ecosystems to function as normal in the second half of the night.

These results are quite encouraging. Local authorities can save money and energy from street lighting and help nocturnal ecosystems recover from light pollution at the same time.

So there’s no evidence that the switch from HPS lights to LEDs increases the negative impacts of lighting on wildlife, and even better, switching to part-night lighting actually appears to reduce them. By switching lights off at midnight there is the potential to tackle two issues at once – reduce energy bills and the ecological impact of light pollution.The Conversation

Callum Macgregor, Postdoctoral research associate, University of York

Wallace, Darwin and the night shift

Last week I had the great honour of attending the Royal Entomological Society’s annual conference, this year hosted by Edge Hill University, to accept the 2017 Alfred Russel Wallace Award. The award is given for the PhD thesis “judged to make the most significant contribution to entomology in the year”, and after several rounds of selection my own thesis, “The role of moths as pollinators, and the effects of environmental change”, was chosen. At the conference, I said that I was particularly proud to receive an award in Wallace’s name, because of his own connections to the subject matter of my thesis – nocturnal pollination by moths. In this blog, I re-tell the story of that connection…

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It is 25th January, 1862, and Charles Darwin is writing to his friend and confidante Joseph Dalton Hooker. Earlier that same day, Darwin had taken delivery of a box of specimens of exotic orchids from James Bateman, a Staffordshire-based orchid specialist.1 Among these, Darwin found one in particular (Angraecum sesquipedale, a species from Madagascar) to be remarkable, due to the great length of the nectary, extending 11.5 inches below the flower. “Good Heavens”, wrote Darwin, “what insect can suck it”.

Angraecum_sesquipedale.png
(L-R) a drawing of Angraecum sesquipedale by W.H. Fitch, included in: James Bateman (1876) A second century of orchidaceous plants. Curtis’s Botanical Magazine; two flowers of A. sesquipedale (© Michael Wolf | Wikimedia Commons | CC BY-SA 3.0); a plate commissioned by A.R. Wallace depicting the hypothetical hawkmoth pollinator of A. sesquipedale, drawn by T.W. Wood and included in: Alfred Russel Wallace (1867) Creation by Law. The Quarterly Journal of Science, 477.

Darwin must have acted quickly. In the same letter to Hooker he had described his “infinite satisfaction” at the prospect of correcting the proofs of his next books, Fertilisation of Orchids, “in 2 or 3 weeks”. Yet when Orchids emerged less than four months later on 15th May, Darwin had revised the text, incorporating a discussion of A. sesquipedale and a rough hypothesis as to its insect pollinator. Reasoning that the longest tongues among English insects belonged to hawkmoths (family Sphingidae), he wrote:

in Madagascar there must be moths with probosces [sic] capable of extension to a length of between ten and eleven inches

Darwin’s prediction sparked debate; among those who sprung to his defence was Alfred Russel Wallace. Contrary to popular opinion, correspondence between Darwin and Wallace was friendly and reasonably frequent after they jointly proposed evolution by natural selection (van Wyhe & Rookmaaker 2015). Five years after the publication of Orchids, Wallace’s Creation by Law asserted not only that Darwin’s predicted moth could safely be assumed to exist, but further, that naturalists visiting Madagascar “should search for it with as much confidence as astronomers searched for the planet Neptune”. Wallace picked out one moth in particular to back up this statement – Xanthopan morganii, then known from tropical Africa (as Macrosila morganii), which had an exceptionally long proboscis.

Xanthopan_morgani.png
Xanthopan morgani; a specimen from continental Africa. Malagasy X. m. praedicta have proboscides several inches longer still!

Several decades later, Walter Rothschild (2nd Baron Rothschild) and Karl Jordan described a newly-discovered subspecies of X. morganii, from Madagascar. Remarkably, the subspecies had a tongue that was, by several inches, longer than that of its continental cousins. In honour of the predictions made by first Darwin and later Wallace, the new subspecies was named X. morganii praedicta.

DarwinWallaceRothschild
(L-R) Charles Darwin, Alfred Russel Wallace, and Walter Rothschild

At this point, the trail went cold for the best part of the 20th century. We had the flower, and we had found the moth with a proboscis to match it, but the final proof of their association was lacking because nobody had ever seen the two interact. That state of affairs lasted until the early 1990s, when Professor L.T. Wasserthal (then of the Friedrich-Alexander University Erlangen-Nuremburg) finally photographed, beyond doubt, the pollinator of A. sesquipedale. It was, indeed, X. morgani.

BotanicaActa
Making the front cover, a photograph of Xanthopan morgani praedicta visiting the flower of Angraecum sesquipedale finally resolves the mystery!

As a final chapter, the video below is well worth a watch: both for its remarkable footage, shot in 2004 by Dr Philip DeVries of the University of New Orleans, of this pollination interaction in action, and for the sheer joy and excitement shown by Dr DeVries and his colleagues when their hard work finally paid off!

If you want to learn more about this story, I owe a debt of gratitude to the review of Arditti and colleagues (2012), on which I drew heavily whilst researching this blog.

1: The relationship between Darwin and Bateman must have been complex. Bateman was, at this time, one of Britain’s foremost experts on, and cultivators of, orchids, and it is hard not to assume that he and Darwin corresponded while the latter prepared Fertilisation of Orchids. However, this box of specimens, and a brief subsequent exchange of letters, appears to be the only surviving evidence of direct interaction between the two (Darwin Correspondence Project). Bateman lived at Biddulph Grange in Staffordshire, designing (with his wife Maria) its famous landscape gardens, which are now owned by the National Trust. The gardens featured a Geological Gallery, seen as a direct attempt to refute Darwin’s theory of evolution by natural selection by drawing connections between evidence from the fossil record and the account of creation given in the book of Genesis.

References

Arditti, J., Elliot, J., Kitching, I.J. & Wasserthal, L.T. (2012) ‘Good Heavens what insect can suck it’–Charles Darwin, Angraecum sesquipedale and Xanthopan morganii praedicta. Botanical Journal of the Linnean Society169, 403-432.

Darwin Correspondence Project, “Letter no. 3356,” accessed on 3 April 2018, http://www.darwinproject.ac.uk/DCP-LETT-3356. Also published in The Correspondence of Charles Darwin, vol. 10.

Van Wyhe, J. & Rookmaaker, K. (2015) Alfred Russel Wallace: Letters from the Malay Archipelago. Oxford University Press, Oxford.

I’m a moth lover but London’s ‘toxic caterpillars’ worry even me

Callum Macgregor, University of York

File 20180502 153866 1eowuy1.jpg?ixlib=rb 1.1Sarah2 / shutterstock

Moths are the insect we truly love to hate. The press report almost annually on the looming threat of clothes moths. I have previously written in defence of diamondback moths, a migratory pest of cabbage crops, and highlighted the quirks of biology that drove the spectacle of thousands of Silver Y moths gatecrashing the Euro 2016 final without tickets. I am absolutely unapologetic about my love for these diverse and intriguing cousins of the much better-loved butterflies. Moths get a bad press thanks to a few species which negatively affect our lives (this also applies to other insects, such as wasps), but most are harmless (or beneficial), fascinating, and often even beautiful.

And so we come to recent news reports of a plague of toxic caterpillars descending on London. The caterpillars in question are those of the oak processionary moth (Thaumetopoea processionea, or just OPM) – just about the only species for which I struggle to summon up much sympathy.

So what’s the issue?

Delicately sketched in pencil, the adult oak processionary moth.
Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org, CC BY-SA

It’s not to say that this is an unattractive moth. The grey-black colour scheme of the adults, active in late summer, lends them the look of having been delicately sketched in pencil. You are much more likely to encounter the caterpillars, which are covered in very long, white hairs. Colonies of OPM caterpillars form white silk nests on oak trees and can be spotted moving about in remarkable nose-to-tail processions. Other moth species form similar nests in the UK, including occasionally on oak: if such a nest is found outside London (especially in Essex or Cambridgeshire), it is more likely to be the Brown-tail moth.

Keep an eye out for OPM caterpillars moving in crocodile-formation between oak trees.
OlegD / shutterstock

Unlike the Brown-tail, however, the oak processionary moth is not native to the UK. It was first recorded in Britain in 1983, but the species established properly in around 2006, when it’s believed some eggs arrived on imported oak trees. This isn’t in itself a reason to dislike OPM, as conservationists (including myself) can sometimes be hypocritical about non-native species: for instance, we are vocally concerned about the arrival of the horse-chestnut leaf-miner moth because it harms horse chestnut trees – even though the trees themselves are non-native.

However, OPM is also a potentially a public health problem. Each of the caterpillar’s hairs contains a toxin called thaumetopoein. Touching an OPM caterpillar directly could bring you out in a rash – in fact, as a general rule it’s always best to avoid hairy caterpillars unless you know what you’re dealing with. The hairs of OPM caterpillars can also break off and drift on the air and, if there are sufficiently high densities of caterpillars, these hairs can cause rashes and respiratory problems even to bystanders.

Besides affecting people, OPM can also impact the oak trees on which it feeds. A particularly severe infestation could strip a tree completely bare of its leaves, though few cases of this taking place in the UK have been reported.

Tackling the problem

Most people agree that something needs to be done, although the NGO Butterfly Conservation argues that, rather than tackling the moth wherever it appears, control efforts should focus on areas where the threat to human health is high or large numbers of trees are at risk of death. Nevertheless, controlling OPM outbreaks is difficult. The nests are constructed in the crowns of oak trees when they are in full leaf, and even if they can be reached, removing them manually requires full protective equipment to ward off the toxic hairs. For that reason the preferred approach is currently to tackle nests remotely, spraying trees with insecticide when the moth is most vulnerable – as a young caterpillar, between April and June.

There is currently no insecticide that is specific to OPM, so a bacterium known as “Bt” is used. Unfortunately, Bt is toxic not just to OPM, but to the caterpillars of all moths and butterflies. The financial cost of these control efforts is astronomical – estimated at around £1.2m per year in 2016-17.

The uncounted, and incalculable, cost to the oak woodland ecosystem could be greater still. The loss of much of the insect biodiversity from our woodlands would be tragic in itself but is likely to have further implications for the bats, birds and other wildlife that rely on these insects for food during their breeding seasons – a study of an OPM control programme in woods near Pangbourne, Berkshire, suggested that blue and great tits were breeding less after spraying took place. It’s these losses that have put me off OPM.

The attractive green silver-lines moth inhabits oak woodland, and is among the species likely to lose out from attempts to control OPM.
Hildesvini

Looking to the future

But let’s not panic – there are plenty of reasons to feel hopeful about the future of Britain’s oak woodlands. It’s true that the moth has been recorded “across vast regions of the south-east”, but that mostly only refers to the highly-dispersive males. To spread the outbreak requires the egg-laying females to travel, and they don’t fly nearly as far. This means that, for now, the toxic caterpillars are mainly confined to London. The outbreak has crossed the M25 ringroad in just a few places, and is still only expanding at a slow pace.

Encouragingly, some of the more isolated sections of the outbreak also appear to be coming under control. New outbreaks in Watford, Barnet, and Pangbourne all appear to have been successfully removed. An outbreak at Bethlem Hospital, Croydon, estimated to contain 4,000 nests in 2012, was confined to just four trees by 2016. Vigilance is key, and this year the Forestry Commission is once again asking the public to report any potential sightings of OPM through its Tree Alert scheme.

Finally, we may have some unexpected allies on our side. In its native southern and central Europe, OPM is not especially problematic because it rarely reaches sufficiently large population densities. That’s partly because its numbers are kept in check by its natural enemies – parasitoids. This is a catch-all term for various insects with a rather gruesome life-cycle: eggs are laid inside caterpillars and other insects, before the larvae eat their victim from inside out (killing it in the process) and emerge as a fully-formed fly or wasp ready to seek out new prey.

The ConversationOften, when an insect expands its range by artificial means (as OPM did, entering the UK on imported trees), it can take some time for its parasitoids to catch up, and in this lag period the insect may do particularly well. However, a recent study found nearly half of the OPM caterpillars sampled from the Croydon outbreak in 2014 were infested by one such natural enemy, the Carcelia iliaca tachinid fly. This suggests the oak processionary moth may be reaching the end of its lag period in the UK, and as the flies attack more caterpillars, this could help the control efforts. My enemy’s enemy is truly my friend, and in this case, perhaps it is a tiny fly.

Callum Macgregor, Postdoctoral research associate, University of York

This article was originally published on The Conversation. Read the original article.

“Protecting Scotland’s honeybees” – but at what cost?

This post was originally written as a guest blog for Mark Avery’s excellent Standing Up For Nature, and I have reproduced it here. Please head over to Mark’s blog to read the comments (and my responses), and for all the latest on Mark’s campaigns, including #BanDGS.

Callum Macgregor is a postdoctoral researcher, currently based at the University of York. His research interests cover the ecology and conservation of pollinators (especially butterflies and moths) under the influence of human-induced environmental change. In his private life, that passion for insects extends to all wildlife, especially birds, and a particular enthusiasm for raptors and owls has led him to support the #BanDGS campaign. You can find him on Twitter at @Macgregor_Cal.

“Protecting Scotland’s honeybees” – but at what cost?

I have tried to link to my sources wherever possible in this blog. In another hat, I am an active promoter of ‘open science’ – the work of most scientists in the UK is publicly-funded and I believe that, by rights, the public should have free access to read their results. I’ve made every effort to choose sources for this blog that are available for all to read – either Open Access scientific papers, reputable journalistic reports, or bloggers that I trust. In a few cases, though, some of you will hit the academic paywall, and will only be able to read the article abstract. For this I apologise.

Last week, the Raptor Persecution UK blog reported on a reception hosted by the pro-driven grouse shooting ‘The Gift of Grouse’ organisation at Holyrood. RPUK were invited along by Andy Wightman MSP (Scottish Greens); besides them, the event was attended by a (small) number of MSPs, and a range of parties with vested interests in driven grouse shooting. Their report on the event is well worth a read. For me, as an ecologist whose research interests tie into the conservation of wild pollinators, one thing in particular caught my attention.

Among several photos taken at the event by RPUK was one showing a pamphlet handed out by The Gift of Grouse at the event (that photo is reproduced here by kind permission of RPUK). The pamphlet details the ways in which grouse moors are, apparently, conservation hotspots (though RPUK themselves have previously debunked the line referring to 81 bird species), and makes the claim that grouse moors contribute to the “conservation of heather moorland – essential to the production of heather honey and protecting Scotland’s honeybees”.

Gift of Grouse pamphlet(RPUK)
That pamphlet from the ‘Gift of Grouse’ (photo by Raptor Persecution UK)

Honey bee woes

It turns out that grouse-shooters have been pushing this angle for a couple of years at least (and regular readers of RPUK will be intrigued to see the prominence of the Hopes Estate in the linked article). You can certainly understand why proponents of grouse shooting would want to jump on this particular bandwagon. Recent declines in honey bees are widely reported in the media. As recently as 2014, a poll by Yougov found the British public considered declining bees to be the most important environmental issue of all – more so even than climate change – and bees to be the single species most worthy of conserving. The hysteria centres around so-called “Colony Collapse Disorder”, a phenomenon where honey bee hives are abandoned by their worker caste; it began in 2007, when American bee-keepers first reported much higher losses of overwintering hives than expected. Declines have continued since then, with neonicotinoid pesticides and varroa mites the most high-profile suspects among a wide range of candidate causes.

People are concerned, because honey bees are important – enormously so. Around 35% of global production comes from crops that are dependent on pollination by animals; and no animal species makes a larger contribution to this figure than honey bees. In the UK, bee-pollinated crops include such favourites as strawberries and apples, as well as the oil-seed rape that paints vast swathes of the English countryside in yellow every year. Their economic contribution is huge.

So you might be surprised that two weeks ago, an article was published in the highly-regarded journal Science arguing that declines in honey bees should not be viewed as a conservation concern (the paper itself is behind a paywall, but you can read the authors’ press release). The authors (Jonas Geldmann and Juan González-Varo, both researchers at Cambridge University) make a strong case that we should view the provision of crop pollination in agricultural settings as an entirely separate issue to the conservation of wild, native pollinators (and they are not the first to tackle this issue). They argue that, in settings where honey bees are not actively contributing to agricultural production, they do more harm than good.

Conserving wild pollinators

Like honey bees, wild bees (which also contribute to pollination) are also in decline. So are moths, butterflies, hoverflies – in fact, almost all of the main groups of pollinating insects. Back in the autumn, a study showing that flying insects had declined by 75% on German nature reserves made the front pages. The causes of these declines are likely to overlap heavily with the factors threatening honey bees – for instance, neonicotinoids are also thought to be important here. But crucially, honey bees themselves are also thought to play a role in these declines. Their impact is twofold – providing competition to wild pollinators for access to pollen and nectar, and introducing and spreading diseases to wild populations as beehives are moved from place to place. These effects can even cascade further into ecosystems, as declines in wild pollinators cause reduced reproductive success in native flowers that are unable to fully benefit from honey bee pollination.

Therefore, our actions in different places and habitats should be determined by our goals. If the goal is to boost crop pollination, then we should treat honey bees for what they are – a managed agricultural animal, like cows or chickens. This is not such a far-fetched comparison as it might seem. Beekeepers move their hives around to make the most of available resources, such as mass-flowering crops (in the process, boosting pollination in those crops, with tangible economic benefits to farmers). They medicate them to stave off the diseases that always accompany unnaturally high densities of animals, and artificially supplement their diets when food is scarce. There is no such thing as a wild honey bee in the UK, and they might not even be native.

Going to the heather

On the other hand, if the goal is to conserve pollinators, then we should do what’s best for wild pollinators. In part, that means increasing not just the quantity, but also the diversity, of flowers. This brings us back around to grouse moors, which do provide an enormous amount of nectar for a short period in August – in simple terms of the quantity of nectar provision, heather is one of the biggest producers in the UK. Some beekeepers take advantage of this, by “going to the heather”. The result is a high-end product that supermarkets sell for 3-4 times more than basic ‘mixed blossom’ equivalents. It’s nice – I have a jar in my cupboard (though it’s not from a grouse moor!).

The impacts of grouse-moor management – particularly muirburn – on floral diversity are complex. In naturally fire-prone ecosystems, such as the Mediterranean, wildfires are an important source of disturbance. Many annual plant species have evolved to respond to fires by flowering, which can lead to much greater quantity and diversity of flowers in the years immediately following a fire – though research I am currently involved in suggests that not all wild pollinators are able to capitalise on this. Through these processes, naturally-occurring fires of a range of sizes and with different time intervals between them (termed ‘high pyrodiversity’) can lead to an improvement in landscape-level biodiversity.

But Britain’s upland ecosystems are not naturally fire-prone, so much of the native flora is not adapted to recover. Moreover, muirburn leads to fires of roughly controlled size at controlled intervals – and so, very low pyrodiversity. A 2011 study led by researchers from the University of Liverpool reported that muirburn does maintain the current level of floral diversity, preventing a complete monoculture of heather; but that this current level of diversity is severely degraded compared to what our uplands should naturally look like (a topic covered on Mark’s blog previously). Moorlands are also less botanically diverse than other semi-natural or natural upland habitat types (see section 3.2.5 of the RSPB’s review of grouse moor biodiversity).

The problem with this low plant diversity is that nectar resources may be in short supply outside of the relatively short flowering period of heather, especially in the hugely-important springtime. Pollinators need a range of flowers, blooming at different times throughout the summer, to provide a constant supply of food. Beekeepers can time their visits to coincide with the heather. Wild bees don’t have that luxury, and those that are present will need to make the most of the temporary glut. Honey bees will provide competition during this time for floral resources and introduce diseases that will harm native moorland pollinators. Other aspects of grouse moors are also problematic – for example, the lack of trees is likely to exclude the many species of solitary bees (and one bumblebee) that nest in tree holes. We are talking about a worst-case scenario on grouse moors for wild bees and other pollinators – a degraded version of an already low-quality habitat. To argue that this is important for production of heather honey is perhaps true. To argue that it is vital to the conservation of honey bees is like saying that we should protect grassy pastures – for the benefit of cows.

Regular readers of Mark’s blog will be well aware that grouse-shooting interests often try to paint themselves as ‘conservationists’, with the best interests of upland wildlife at heart. They will also be aware that these claims are frequently misplaced: being generous, they appear to be based on a fundamentally-flawed view of what a healthy upland ecosystem should look like. The Gift of Grouse’s claim that grouse moors help honey bees seems to be another example of a wildly misguided attempt to align grouse-shooting with conservation interests. Please don’t fall for it!

Lived and learned: #BES2016 in review

I returned last night from the 2016 Annual Meeting of the British Ecological Society, held in Liverpool. Going to ‘the BES’ is fast becoming an annual tradition for me, as it is for hundreds of ecologists. As always, I had a great time, and learned a lot – not just fascinating snippets from the coalface of ecological science, but also a lot of more general lessons about how to get the most out of big conferences like this one, and a scientific career more generally. For my own sake as much as anybody’s, I thought I’d coalesce some of those thoughts here.

1. Engage with the public (don’t preach at them)

The conference was book-ended by talks that addressed the difficulty of turning your science into practice. Much of what ecologists do has a real-world application – whether we work in conservation, monitoring, or environmental change, I think we all want to see our research getting used, but it isn’t always as simple as ‘publish the paper, wait for people to read it’. Opening the conference, Mike Begon tackled Michael Gove’s comments that “people have had enough of experts”. Mike pointed out that people are more likely to respond to emotionally attractive messages than plain facts, no matter how persuasive those facts may be – but importantly, there is no reason why we can’t use facts as the moral justification to underpin those messages.

Later, in the final plenary, Hugh Possingham distilled his own experiences of trying to get his research into policy in his native Australia into the three simple messages in the tweet above. Hugh also highlighted the importance of ‘environmental heroes’, who can campaign on an issue over much longer timescales than is really possible for an academic. Somebody who definitely qualifies as an environmental hero retired this week after 13 years as CEO of Butterfly Conservation – best wishes for the future to the wonderful Martin Warren.

2. Step outside your comfort zone

This year’s conference marked the first time I had presented a chapter of my PhD (and hopefully soon a paper) that tackled DNA-based approaches for detecting ‘stuff in the environment’ and tested whether they could be applied to my area of interest, pollination interactions. I’m getting fairly experienced now at presenting talks at conferences – I’ve done both small conferences (where, conversely, the audience tends to be larger) and big conferences (where the audience can be much more topic-focussed and expert). But this was a methodological talk, about skills I had almost entirely learned within the last 12 months. What if I got found out?

I needn’t have worried. My talk went well and people seemed to be interested (and some of them said very nice things on Twitter!). A couple of people came up to chat afterwards who, it turned out, worked in related fields and had found elements of my talk useful – making those kinds of contacts was exactly why I’d wanted to give the talk in the first place!

On a related note, I spent Wednesday afternoon chairing a session on Global Change Ecology. Again, something I had never done before, but it worked out great, serving as simultaneously a gentle and a rigorous introduction to session-chairing. Gentle – because it was a small session in a big room, so it never felt too intimidating. Rigorous – because I faced all the challenges that chairing can throw up (speakers worried about their timing, stony silences when asking for audience questions, and at one point a hint of technical issues!). Next time I’m given the chance to chair a session, I’ll be much more confident.

3. Be nice

In a year of celebrity deaths, ecologists mourned the loss of Ilkka Hanski. I recently submitted a paper, based on my dissertation project, that investigated the spatial ecology of a moth species, and so I have a little familiarity with Ilkka’s work on metapopulations. Therefore, I decided to attend as much as I could of the session on Tuesday afternoon celebrating his life’s work. That such a session took place at all was remarkable – how many past attendees of the BES must pass on every year? – but I was struck by both the high turnout and the extraordinary fondness with which each speaker talked about Ilkka. Something to aspire to.

The following morning, Alison Hester – charged with the impossible task of giving the 12 Months in Ecology lecture after the year that’s been! – did a marvellous job of reminding us that it’s not all doom and gloom. There have been some fascinating discoveries this year, and great progress on the issue of microplastics. With Brexit looming and the election of President Trump, it’s easy to feel down – but it’s not certain how things will pan out, and maybe we ecologists, as a collective, can make a difference.

4. You’re not an imposter!

Imposter syndrome – almost all academic scientists will be familiar with it (as a side-note, congratulations to the BES for being proactive in organising a workshop about stress, and especially for targetting it at PIs, to help them look after their students. A great shame it had to be cancelled at the last minute, and I hope it will be back on the programme next year). After last year’s conference, I was honoured to have been named a runner-up for the Anne Keymer Prize for Best Student Talk. On Tuesday evening, I was invited to a drinks reception attended by Society prize-winners, current and past Presidents, and this year’s plenary speakers. Wow – I was terrified! Fortunately, the lovely Zoe Davies (who really did a marvellous job of putting this year’s programme together) spotted me looking nervous and swept me up, immediately introducing me to “Bill” (that’s Bill Sutherland to us mere mortals!). Within the hour I was chatting away to “Pedro” and “Jordi” – authors of this year’s Marsh Book Award winnerMutualistic Networks – about my own research on nocturnal pollination networks. Of course, I still felt like an imposter – but if anybody in the room felt in any way superior to me, they hid it well. Some of the best ecologists around – but totally grounded and humble.

5. The more you see, the more you know

This was my third BES; since starting my PhD I’ve also done two Royal Entomological Society conferences, two Butterfly Conservation/De Vlinderstichting conferences, and a host of other smaller meetings. At the first of these, I knew practically nobody and spent large chunks of the meeting standing awkwardly by my poster. This time out, it took me until Wednesday lunchtime to finally catch up with everybody I’d hoped to see at the BES, despite ‘networking’ during every single break. Along the way, I met a bunch of new people, ranging from MSc students to high-profile PIs, many of them through introductions by my existing contacts. I’m astonished by how many friends I’ve made in three short years in academia – long may it continue.