A Hard Rain's a-Gonna Fall

As I slurped my second - desperately needed - coffee on Wednesday morning I watched a covey of partridge percolate out of the field margin and delicately pick their way through the neatly drilled, shoulder-high rows of winter wheat {{1}}. The field slopes away gently to the East and, although the partridge were blissfully unaware of it, was the site of major excavations through August and September as several hundred metres of drainage pipes were installed.

The drainage and the partridge reminded me that, although things appear timelessly bucolic, the environment is never static as new challenges (or threats) to the status quo are introduced by humans.

The partridge? These are Red-legged partridge (Alectoris rufa), a non-native species, released in their millions every year for shooting. I've not lived in this area long-enough, but in Fife their numbers always plummeted overwinter (and not just through 'lead poisoning') and they rarely bred {{2}}. But in November the fields and hedgerows are thick with them as they busily eat insects and seeds that would normally be fattening up the native finches for the long winter ahead.

This area contains a mix of good arable and pastoral land and has been intensively farmed for hundreds of years. The field with the partridge has probably had a succession of wheat, barley and - more recently - oil seed rape (OSR) grown in it for generations, yet it is only now that the farmer has installed additional drainage.

Perhaps the newly-drained region has always been boggy?

Alternatively, perhaps our changing climate - warmer, wetter winters and hotter, drier summers - explains the need for additional drainage.

There are interesting parallels between the introduced partridges and our (also non-native) honey bees; both compete for natural resources, sometimes to the detriment of the 'local' native species, and both may introduce - or aid the spread of - novel diseases (Millán, 2009).

However, this week I'm going to introduce (as there will inevitably be more on the topic than I can cover in 2-3k words) the impact of climate change on beekeeping.

Improving the drainage for boggy apiaries might be the least of our problems 😞.

What is climate change?

Global warming and climate change are often used interchangeably when, in fact, one leads to the other.

Global warming refers to the increase in average global temperatures. Since the industrial revolution the earth's average surface air temperature has increased by about 1.5°C. This average naturally varies, but the marked increased post global industrialisation is due to the influence of human activity.

As the temperature rises, so does the amount of water vapour in the atmosphere. The increased water vapour - ~7% per degree Celsius - absorbs heat radiated from earth, preventing it escaping ... thereby creating a positive feedback loop that leads to more warming.

And this results in changes to the climate - the amount of rainfall, storms, droughts etc.

Consequences of climate change

That water vapour doesn't just stay in the atmosphere. It condenses as it cools - for example over mountains - forming clouds and these produce rain. With more water vapour, rainfall will become more intense.

It's likely that there will be a 2-3 fold increase in what the Intergovernmental Panel on Climate Change (IPCC) calls 10-year and 50-year 'events'; i.e. before global warming you might have expected to see heavy precipitation and consequent bad flooding once a decade, with even more dramatic deluges once every 50 years.

The type of devastating flooding in Valencia, resulting from almost 500 mm of rain in just 8 hours, will happen more frequently.

In addition to the intensity of rainfall increasing, the periods when it rains (and when it does not rain) will change.

We can expect warmer, wetter winters, and hotter, drier summers.

That's not the same as warm, wet winters and hot, dry summers ... there will still be hard freezes in the winter, and heavy rain in the summer.

Global warming is uneven. The Arctic is warming almost four times faster than some other regions and this discrepancy in temperatures is changing the speed of the jet stream, the strong, high altitude, winds that 'distribute' the cyclonic storm systems around the earth. With reduced jet stream speeds, heat domes develop, trapping warm air and resulting in markedly elevated temperatures at a continental scale.

In fact, heat extremes - both in terms of the temperatures reached and the period over which temperatures are elevated i.e. droughts - are expected to also increase. July 2022 saw the first recorded daytime temperature over 40°C in the UK, and the duration of droughts is also increasing here.

Higher temperatures and prolonged droughts will result in more wildfires.

Is that it?

Well, that lot sounds bad, but perhaps not catastrophic.

Is it sufficient to locate your apiaries in regions that cannot flood, provide water during periods of drought and take care not to torch the tinder-dry herbage with a carelessly placed smoker?

Well, that's a start, but I'm afraid those are the easy bits.

Natural variation

Before continuing, it's worth emphasising that these major climatic events will occur sporadically - just a bit more frequently - amongst the natural variations we usually see.

Some seasons will be absolutely 'normal' ... a little wetter, or drier, or warmer or colder perhaps, but nothing out of the ordinary.

These are the typical year-on-year variations you've already experienced; my back-of-an-envelope records suggest that one year in four is 'good', about the same number are 'poor', and about half of them can be considered average.

Of course, it might not be the entire season that's good, poor or average.

My 2023 summer honey crop was worse than hopeless, but the spring had been great. This year, spring was no better than average but I had to buy a load more buckets for the summer bonanza. When comparing queen mating, 2023 was easy-peasy, but I struggled for weeks through the intermittently damp summer this year (it was clearly damp enough to keep the nectar flowing, but not so damp that they couldn't forage).

Of course, whether it's good, poor or average rather depends upon how you 'score' a successful beekeeping season.

If you've kept bees for a few years you'll be well aware of the differences a good or poor season - weather-wise - makes to your honey crop or the ease with which your queens get mated.

This natural variation will be overlaid by an inexorable increase in average temperatures, this will result in an increased frequency of 'freak' weather events and insidious - but probably more damaging long term - changes to the environment.

Why more damaging?

If a devastating flood or wildfire wipes out your apiary on average every 25 years rather than every 50 years you'd probably have to spend a lifetime beekeeping to notice the increase.

Yes, it's awful if it happens - for you and the bees - but it's very, very rare, and it might not happen at all.

However, if every year is a little more tricky - less forage, less time to forage, more pests, more pathogens, new pests and pathogens, longer droughts etc. then beekeeping becomes more difficult ... and being a bee becomes harder.

Average or worse years will predominate even more, good years will get less common and bad years will both increase in frequency and severity.

Death by a thousand cuts ...

Those who find beekeeping easy will find it more difficult. Those who find it difficult already might find it impossible.

So what are the changes - other than more and heavier rain, longer droughts or higher temperatures - that might be expected from a warming world?

What changes in a warming world?

Broadly the changes fall under three broad headings; pests and pathogens, forage and honey bee biology.

Each of these is an enormous topic in it's own right, so I can do little more than give a couple of examples of what might happen ... or, in some cases, what is already happening.

Pests and pathogens

As the earth warms, the global distribution of species changes. Some of these species are pathogens - the bacteria, fungi and viruses that cause disease - and others are parasites that transmit these pathogens or predators that directly target honey bees.

Global trade exacerbates this. The Yellow legged hornet (Vespa velutina) was introduced to France with a shipment of pottery and has spread throughout north and western Europe.

Yellow legged hornet

The UK would expect irregular incursions from this French population, carried here by strong Southerly winds, or caravaners {{3}}. However, the subsequent successful reproduction and overwintering depends upon the climatic conditions in the UK.

It's notable that far more Yellow legged hornet nests were reported in the autumn of 2023 (#73) than this year (#23 to date; data from DEFRA). The mean winter temperature in '22/'23 was appreciably warmer than '23/'24, and up to 4°C warmer than a 30 year average. Genetic studies have confirmed that some nests are from overwintered queens and, with continued global warming, I expect the hornet to become established in the UK (and, if not already, then soon).

Temperature is a major driver of range expansion in invasive wasps (Zhang et al., 2024), and we can expect further increases in the geographic distribution of the Yellow-legged hornet - north and west in the UK, and probably more widely in the US - as average temperatures increase.

Varroa management

Varroa already has a near-global distribution. Successful management of the mite, at least in temperate regions, usually depends upon the application of miticides in late summer and a second application during the winter.

The late summer application reduces the mite population and so prevents the exposure of the developing winter bees to mite-transmitted viruses.

The equally important winter treatment minimises the mite population for the season ahead, effectively mopping up mites that were missed earlier, or that subsequently managed to reproduce during late-season brood rearing by the colony.

For maximum efficacy, this winter treatment - typically of oxalic acid - should be applied when the the colony is broodless.

A warming world will ...

• increase the winter mite population if the colony rears brood later into the autumn
• decrease the efficacy of the winter treatment as the likelihood and/or duration of broodless periods will be reduced

My colonies are routinely broodless for much of November. As winters warm I expect this period to decrease, making it more difficult to apply treatment at an optimal time.

As before, remember that these changes will be incremental ... I will only notice the changes in retrospect after many years (and if my memory doesn't fail 😉).

Nevertheless, the changes will be significant over time ... a mistimed application one season will see mite numbers explode the following year, with potential colony losses. As correct timing of the winter treatment becomes more problematic - or, in more southerly latitudes, broodless periods routinely disappear - parasite/virus-associated losses will increase, and/or will require more vigilance at other times of the season.

Assuming no 'magic bullet' is invented to cure the Varroa problem {{4}} I expect new treatment regimes will be needed and that these may impact the productivity of the hive, measured in terms of brood production and/or honey gathering.

But there are other factors that will influence the honey crop.

Forage

Climate extremes will have a direct impact on the flowering and pollen/nectar production of the forage plants that our bees exploit.

Late frosts destroy blooms, heavy rain dilutes nectar (e.g. rain-washed Acacia flowers are no longer attractive to bees), strong winds prevent flight, flooding might wipe out an entire crop and prolonged drought inhibits nectar production.

But there are more insidious changes that will also have an impact.

There's a synchrony between plants and pollinators (see Freimuth et al., 2022). Global warming is changing this.

Historically, pollinator populations - and you can think of this as the foragers in your colony of honey bees, or a much wider group of native pollinators - were a bit ahead of the plants upon which they forage. Populations would increase before plants were in full bloom.

However, plants respond faster to global warming than pollinators, so populations are now more synchronous.

This sounds better ... but isn't.

The plants aren't pollinated quite as well, and the maximal pollinator population occurs a bit late for the peak of the flowering period.

But, with continued global warming, we can expect the asynchrony to increase again. Early flowering plants might end up flowering too early - this means that the temperatures may be insufficient for foraging.

So what?

In the immediate term, colony development will be significantly impaired ... smaller colonies mean a smaller honey crop, less resistance to robbing and more overwintering losses.

And what happens to the plants? Because they flowered 'too soon' they will be poorly pollinated, as a result of this they will be less able to compete with wind-pollinated plants with which they share the environment.

Climate change is likely to result in marked changes in both the flowering times of plants/trees, and in their distribution in the environment.

Some environments might get better for bees, others will get substantially worse.

Finally, forage and pests/diseases are also inextricably linked; poorly nourished colonies, for example with brood reared during periods of pollen shortages, are less resistant to disease ... both the ones we know of, and new ones.

Honey bee biology

Again, an enormous topic, but let's just consider two brief examples.

Colony development

With changing environmental conditions - both in terms of forage availability and the weather - it's likely that colony development will sometimes be impaired. Prolonged droughts will reduce nectar availability and necessitate more effort on water gathering and nest cooling. Excessive temperatures may result in overheating, absconding or comb collapse. Increased rainfall will reduce foraging and may result in starvation.

Beekeepers will need to be more vigilant. I expect feeding colonies during the season to become more common, apiaries will need to be re-sited to avoid the full heat of the sun, and water/ventilation routinely provided in regions where this is not normally needed (if you already keep bees in the broiling sun of the Atacama Desert you'll be familiar with all the tricks).

Queen mating

Queen mating is a critical part of the biology of the colony. The number of drones that the queen mates with is important - the more the merrier - as is the timing of these mating flights.

After emergence, the queen matures for a few days and then embarks on a number of short orientation flights. She needs to be able to find her way back to the colony after mating. Once she knows the immediate geography she goes on her nuptial flight(s), visiting distant drone congregation areas. Typically these flights occur between 1 and 4 pm, assuming the weather is suitable.

In studies of RFID {{5}} tagged queens (Heidinger et al., 2014) the average length of a single mating flight was ~18 minutes. Typically queens make multiple mating flights, averaging ~5 in total and ~2 per day. Queens have been observed to take as many as 16 mating flights, and as many as 7 mating flights in a single day.

All of these numbers mean that queens need several days of suitable weather to mate successfully.

And if it's intermittently raining, or windy, or cold these flights are much less likely to occur. Although climate change means hotter summers and more droughts, it also will result in more changeable weather patterns, meaning there may be reduced opportunities for mating flights on sequential days.

Some final arm waving

It wouldn't be The Apiarist without some arm waving speculation ... 😉.

Slightly more nebulously {{6}}, there are other factors that are 'competing' in terms of producing a well-mated queen. These are (in no particular order):

• age - queens usually mate within a week or so, and the longer mating takes the less chance that the queen will be successfully mated
• packing of the spermatheca - can this happen in stages, with the queen going on additional mating flights (perhaps after waiting-out poor weather conditions) or does it happen 24-48 hours after the last mating flight?
• eyesight - exposure to drone semen reduces the visual acuity of queens (see It makes you go blind, it's an amazing story), so reducing repeat mating flights

Individually and together these may impact queen mating success as the climate changes. Drone availability and number will depend upon colony development ... if colonies have been held back drones may be limiting in number. Variable weather during the mating period may result in queens 'going blind' before mating with sufficient drones, in them packing the spermathecae before taking enough mating flights, or in simply getting too old to mate.

Climate change and beekeeping

COLOSS surveys of annual or winter losses often report that 'natural disasters' e.g. storms, flooding, falling trees, account for a low percentage (~1-3%) of losses. I expect this figure to rise, and it can only sometimes be mitigated by choosing better apiary locations. The weather extremes are largely unavoidable, and will increase.

Colony management will get more difficult. Colonies may require additional feeding more frequently, better protection from weather extremes such as droughts, pollen supplementation when particular sources fail, and more rigorous monitoring and intervention for disease management. They will be exposed to new pathogens through changes in their distribution (or inadvertent or deliberate human activity e.g. the Tropilaelaps mite has recently been introduced to Europe, and I expect it to spread more widely), and their innate resistance mechanisms will be compromised due to poor diet.

Yes, the bees will gradually adapt to environmental changes, but this adaption will take millennia, so is unlikely to make beekeeping any easier for readers of this site.

This adaption might involve changes to the bees that make beekeeping yet more difficult ... or at least different. For example, honey bees in Africa exhibit seasonal absconding to avoid periods of nectar dearth, or migration to avoid droughts (Frazier et al., 2024). These processes are not incompatible with beekeeping, but it would involve fundamental changes to the ways colonies are managed.

Recommended reading

This is a big subject and one I will return to. In the meantime, if you want to read more there are a few 'detail-light' reviews of climate change and beekeeping (Le Conte et al., 2008; Neumann and Straub, 2023), published studies of perceived impacts (van Espen et al., 2023; Landaverde et al., 2023), and modelling studies that predict the potential consequences (Rajagopalan et al., 2024), all of which are listed below.

This is not a comprehensive list by any means.

In closing, it's worth noting that native bee populations - those that are not managed - will face exactly the same challenges, but won't have a caring beekeeping nearby to help. There are predicted to be major changes in pollinator distribution (Pardee et al., 2022) - with some winners and losers - and greater declines in bee populations (Miller-Struttmann, 2024).

Much of this literature is relatively new ... it's a hot topic, if you'll excuse the pun. Our understanding is likely to increase with further studies, but we won't know the full extent of the impact of climate change (other than it's generally not going to be good news) for many, many years.

The Met Office has a brief overview of climate change in the UK, and there is a BBC resource that predicts what climate change will 'look like' in your area.

A hard rain's a-gonna fall ... and flooded apiaries are only the start of our problems.

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Notes

A Hard Rain's a-Gonna Fall is a song by Bob Dylan, and appeared on the album The Freewheelin' Bob Dylan in 1963. Although often considered a song about the Cuban missile crisis it was written late in September 1962, a month before the crisis broke.

However, if you read the lyrics of the second verse, the real subject of the song becomes clear:

I saw a room full of men with their hammers a-bleeding

It's obviously about frame building 😉.

References

Frazier, M., Muli, E., and Patch, H. (2024) Ecology and Management of African Honey Bees (Apis mellifera L.). Annual Review of Entomology 69: 439–453 https://www.annualreviews.org/content/journals/10.1146/annurev-ento-020823-095359.

Freimuth, J., Bossdorf, O., Scheepens, J.F., and Willems, F.M. (2022) Climate warming changes synchrony of plants and pollinators. Proceedings of the Royal Society B: Biological Sciences 289: 20212142 https://royalsocietypublishing.org/doi/10.1098/rspb.2021.2142.

Landaverde, R., Rodriguez, M.T., and Parrella, J.A. (2023) Honey Production and Climate Change: Beekeepers’ Perceptions, Farm Adaptation Strategies, and Information Needs. Insects 14: 493 https://pmc.ncbi.nlm.nih.gov/articles/PMC10299425/.

Le Conte, Y., and Navajas, M. (2008) Changements climatiques : impact sur les populations d’abeilles et leurs maladies. 27(2): 485 https://doc.woah.org/dyn/portal/index.xhtml?page=alo&aloId=30769.

Millán, J. (2009) Diseases of the Red-Legged Partridge (Alectoris rufa L.): a review. Wildlife Biology in Practice 5.

Miller-Struttmann, N.E. (2024) Climate change predicted to exacerbate declines in bee populations. Nature 628: 270–271 https://www.nature.com/articles/d41586-024-00681-w.

Neumann, P., and Straub, L. (2023) Beekeeping under climate change. Journal of Apicultural Research 62: 963–968 https://www.tandfonline.com/doi/full/10.1080/00218839.2023.2247115.

Pardee, G.L., Griffin, S.R., Stemkovski, M., Harrison, T., Portman, Z.M., Kazenel, M.R., et al. (2022) Life-history traits predict responses of wild bees to climate variation. Proceedings of the Royal Society B: Biological Sciences 289: 20212697 https://royalsocietypublishing.org/doi/10.1098/rspb.2021.2697.

Rajagopalan, K., DeGrandi-Hoffman, G., Pruett, M., Jones, V.P., Corby-Harris, V., Pireaud, J., et al. (2024) Warmer autumns and winters could reduce honey bee overwintering survival with potential risks for pollination services. Sci Rep 14: 5410 https://www.nature.com/articles/s41598-024-55327-8.

Van Espen, M., Williams, J.H., Alves, F., Hung, Y., Graaf, D.C. de, and Verbeke, W. (2023) Beekeeping in Europe facing climate change: A mixed methods study on perceived impacts and the need to adapt according to stakeholders and beekeepers. Science of The Total Environment 888: 164255 https://www.sciencedirect.com/science/article/pii/S0048969723028760.

Zhang, X., Nie, P., Hu, X., and Feng, J. (2024) Future Range Expansions of Invasive Wasps Suggest Their Increasing Impacts on Global Apiculture. Insects 15: 546 https://pmc.ncbi.nlm.nih.gov/articles/PMC11276961/.

{{1}}: Shoulder-high if you're a partridge.

{{2}}: Red-legs need dry, sandy soils and average midsummer temperatures exceeding 19°C to breed - conditions rarely, if ever, achieved in Scotland.

{{3}}: Or lorries, or whatever ... it's not just caravans that the Yellow-legged hornet stows away in.

{{4}}: And I reckon the probability of this happening is somewhere between 'unlikely' and 'no chance whatsoever'.

{{5}}: Radio-Frequency Identification.

{{6}}: If what's gone before isn't nebulous enough already 😜.