Too many honey bees (on the town)?

Synopsis : Honey bees compete with local bees. What number of hives are too many, leading to injury to local bee populations? Most probably fewer than you suppose.

Advent

A number of years in the past I visited Montréal to talk at a world symposium. It used to be a large convention with an overly busy programme however I nonetheless controlled to sneak away and notice town. We had per week or so of shocking Indian summer time climate so I walked nearly in all places; alongside the banks of the St Lawrence and Prairies Rivers, during the Botanic Gardens and the Mount Royal Park.

If you happen to’ve no longer been I will counsel it.

Then again, I didn’t see a unmarried honey bee.

I wasn’t in particular taking a look for honey bees, however beekeepers generally tend to note this stuff.

Looking back that wasn’t too sudden. At the moment there have been simply a few hundred hives throughout the metropolis, which covers a space of 430 km² .

I did see monarch butterflies (Danaus plexippus) within the gardens, stocking up on nectar prior to beginning their migration again to Central Mexico.

This used to be early October. Had there been a lot of honey bees in Montréal I’d have anticipated to look them at the similar asters, competing for the nectar with the butterflies, piling that can be purchased prior to the approaching iciness.

And pageant isn’t at all times a just right factor.

Save the bees

Scientists have lengthy been conscious about the significance of pollinators (a lot of that are bugs) and the worldwide decline of insect populations. The position of bugs, and the significance of retaining them generally is a tricky factor to ‘promote’ to most of the people.

They’re ceaselessly perceived as wriggly, creepy-crawlies, that may sting … urgh!

With out public make stronger many conservation initiatives will fail.

Expanding public consciousness and related conservation measures, for instance banning pesticide gross sales through lawn centres, is wanted and a mixture of ‘emblem consciousness’, a popular fondness for honey and (inevitably) sloppy journalism signifies that honey bees (Apis mellifera) have develop into the poster woman for insect pollinators.

’Save the bees’ as a slogan is a gross oversimplification of ’building up the quantity and variety of bugs pollinators within the surroundings’ and is typically taken to imply – or interpreted as – ‘advertise honey bees’.

If you happen to’re serious about seeing simply how biased this protection is I like to recommend Smith and Saunders (2016) who collated press articles on pollinators (in Australia) and quantified the other species featured. The name in their paper well defines the issue:

Honey bees: the queens of mass media, regardless of minority rule amongst insect pollinators

The beekeeping ‘explosion’

Partially due to this media protection there was an explosion of passion in honey bees and beekeeping during the last 10-15 years … and a lot of new beekeepers.

Since over 80% of Canadians are living in city spaces an important percentage of those new beekeepers – and their hives – are in cities and towns.

Between 2013 and 2020 the choice of hives in Montréal higher from 283 to ~3000.

With ease – for this put up and the paper (MacInnes et al., 2023) on which it is based mostly – there used to be an intensive survey of Montréal’s city bees in 2013 (Normandin et al., 2017). Through repeating the survey in 2020 it used to be imaginable to resolve the have an effect on of the rise in city honey bees on wild bees and one of the most vegetation on which each rely for pollen or nectar.

This ‘prior to and after’ find out about confirmed that the advent of huge numbers of hives scale back wild bee species richness and pollen availability.

“Too many honey bees” … most likely no longer what you anticipated in a beekeeping weblog 😉 .

Testable hypotheses

The MacInnes find out about had 3 targets, to:

Read about the species richness and composition of untamed bee communities alongside a gradient of honey bee abundances

Assess the affect of honey bee abundance on floral useful resource (pollen) availability

Evaluate the richness and composition of the wild bee communities prior to and after the massive building up within the honey bee colonies in Montréal

The 2918 hives in Montréal don’t seem to be lightly dispensed . The site of a few had been recognized, however within the absence of that knowledge it must be inferred through the frequency of honey bees sampled particularly places … if there are many honey bees it’s affordable to suppose that hive density inside foraging distance is upper than in spaces the place there are fewer honey bees.

Subsequently, through sampling wild bee numbers and species throughout a variety of various websites, in addition to counting honey bee numbers, it used to be imaginable to resolve whether or not the presence of honey bees influenced the presence, quantity and inhabitants make up of different bees.

In a similar fashion, through evaluating the 2020 knowledge with the 2013 survey it used to be imaginable to resolve the affect of the city-wide 10-fold building up in honey bee numbers.

Pageant between bee species – a minimum of on this case – is exploitative.

One bee species exploits a useful resource this is wanted through any other bee species. The obvious issues they compete over are the floral assets – pollen and nectar – produced through crops within the house. It’s imaginable to measure pollen abundance and nectar quantity (and sugar focus, although this will have to no longer alternate in keeping with bee numbers) and, on this find out about, pollen used to be quantified to look if spaces with top numbers of honey bees had much less pollen.

Find out about design

I’m no longer an ecologist so am unqualified to correctly pass judgement on the find out about however – to my unqualified eye – it appears to be like lovely affordable. The paper is freely to be had so pass judgement on for your self . Sampling used to be performed at 15 well-spaced websites throughout Montréal, in forage-rich places corresponding to group gardens, cemeteries and nature parks. Top answer satellite tv for pc mapping used to be used to quantify herbaceous duvet and impervious surfaces (concrete, constructions). Bees had been amassed the use of pan traps the use of a standardised sampling process for the places of the traps, their separation, the period of trapping and the kinds of day on which trapping used to be performed.

For instance, you can’t meaningfully examine 3 hours of trapping on a rainy April afternoon with 6 hours on a phenomenal past due summer time day. Just right foraging days had been selected in June, July (two times), August and September.

Along with pan traps, aerial trapping (believe enthusiastic PhD scholars prancing round swishing butterfly nets) used to be additionally performed in parallel, with samples from each and every web page/date pooled for counting and next identity.

In the end, the similar sampling websites had been used as had been selected within the 2013 survey (although I believe there have been a few further websites used as properly) to permit related comparisons prior to and after the inflow of honey bees.

A couple of definitions

Honey bees … you recognize what those are 😉 .

All different bee species had been thought to be ‘wild bees’ i.e. unmanaged, although they recognize some Bombus species are controlled for pollination services and products, however did/may no longer distinguish those from free-living Bombus.

Inside of those wild bees the authors known ‘local’ and ‘unique’ bees; the latter (~12% of the whole) being offered during the actions of guy.

The wild bees known had been additionally separated into two teams – huge and small – based totally upon the inter-tegula span (ITS). That is the space between the tegulae on the wing bases, and is an excellent indicator of frame mass and wing musculature which, in flip, is a predictor of foraging vary. Bees with a low ITS are small, gentle and most effective forage over brief distances .

Bee communities (i.e. X% of species A, Y% of species B, Z% of species C, remembering the group may comprise a number of dozen species) had been characterized the use of plenty of statistical strategies that I’m additionally no longer certified to pass judgement on correctly (although I’ve printed a number of papers the use of one of the most strategies cited … 😉 ). Pass on, ’fill your boots’ … take a look at the paper and come to a decision whether or not Shannon-Wiener or Simpson’s variety indices are the correct ones to make use of. Those strategies are moderately usual and feature been carried out to the research of bee communities in earlier research, so let’s suppose they’re OK.

Pollen research of white clover (Trifolium repens) used to be additionally performed. Now not all bees use this as a pollen useful resource, however many bees do. Pollen used to be ethanol extracted, stained and counted underneath a microscope (believe unenthusiastic PhD scholars going cross-eyed with boredom … and cursing their manager 😉 ).

Wild bee richness and honey bee abundance

Richness is a measure of the choice of species and therefore variety of the wild bee inhabitants. The speculation used to be that richness would scale back as honey bee numbers higher if there used to be pageant between the bees for restricting assets.

And that’s precisely what used to be noticed.

Those graphs plot honey bee numbers (horizontal) towards a measure of species richness (vertical), with each and every dot being a distinct pattern web page/sampling date. The overlaid forged line and shaded blue area represents a easiest are compatible and 95% self assurance prohibit respectively.

For the reason that line slopes down from left to proper (a damaging slope) it signifies that higher abundance of honey bees leads to diminished species richness within the wild bee inhabitants throughout Montréal (left hand graph). Huge bees and Bombus (bumble bees, that are very huge bees) had been unaffected through honey bee abundance (no longer proven), however small wild bees (proper hand graph) reduced considerably.

The wild bee group make up – the variability of species and the choice of each and every – is reasonably tougher to give an explanation for. Necessarily websites with top numbers of honey bees had been extra very similar to each and every different of their wild bee communities. Websites with low or medium ranges of honey bees had been extra various. This implies that most effective some wild bees can compete within the face of top honey bee abundance.

The have an effect on of beekeeping on wild bee communities

Unsurprisingly, in gentle of the consequences offered above, the ten-fold building up in honey bee hive numbers in Montréal between 2013 and 2020 additionally negatively impacted wild bee richness.

Those graphs plot the distinction in honey bee numbers at each and every sampled web page between 2013 and 2020 (horizontal axis) as opposed to wild bee richness. The forged black line represents the most efficient are compatible of the scattered knowledge issues having taken into consideration different variables corresponding to sampling duration, floral richness, floral density and the quantity of impervious surfaces and herbaceous forage.

Once more, the downwards (damaging) slope of the road as honey bee abundance will increase signifies that wild bee group richness decreases if there are extra honey bees about. As prior to, this used to be no longer noticed in huge wild bees or Bombus, however used to be vital in small wild bees.

If there are will increase of generalist bees – corresponding to honey bees – within the surroundings, the expectancy could be that forage crops, like white clover, could be depleted of pollen and nectar … this used to be the following factor that used to be examined.

Extra honey bees = much less pollen 🙁

White clover used to be extensively dispensed around the pattern websites. It is usually a flower that numerous other bees can get entry to for ‘assets’ (pollen and nectar) … little need for a actually lengthy tongue, or robust jaws to chop during the aspects of the florets.

Simple pickings for a lot of various bees.

Except there are plentiful numbers of honey bees within the surroundings.

The residual pollen on white clover considerably reduced with expanding abundance of honey bees. With not up to 20 honey bees detected at sampling websites, each and every clover flower contained ~24,000 pollen grains. With numbers over 20 honey bees the quantity dropped to ~14,500.

This lower used to be unrelated to different variables examined e.g. the numbers of Bombus at each and every sampling web page.

The belief this is that the higher numbers of honey bees exploit the to be had pollen to the detriment of different bees that may in a different way forage on clover.

Is all of it unhealthy information?

Sadly, sure.

I believe that this is among the higher research of honey bee pageant with wild bee populations that I’ve learn .

It’s value noting one of the most barriers of the find out about.

There used to be no sampling early within the season. The dimensions of honey bee colonies in April/Would possibly most definitely makes them fearsome competition in comparison with solitary queens rising after a iciness’s hibernation. It’s most probably that omission of early season samples underestimates the damaging have an effect on of honey bees on wild bee populations.

Even though the one variable measured that influenced wild bee richness used to be honey bee abundance, most likely the previous declined as a result of adjustments in an unmeasured variable. For instance, most likely the floral variety/group dramatically modified between 2013 and 2020. This information wasn’t amassed in 2013 (however used to be in 2016) however it sort of feels not going that it will be dramatically other.

Botanic gardens and concrete planting typically comprise huge quantities of unique vegetation i.e. non-native. Since local wild bees have co-evolved with local vegetation, this unique planting is typically thought to be to profit unique bees extra.

Of the 120 bee species known, 15 had been unique. Then again, the 13 species lacking from websites the place honey bees had been maximum plentiful had been all local bees.

The advent of huge numbers of ‘unique’ honey bees used to be in particular destructive to local wild bee populations reasonably than different unique bees. Small local bees (~60% of all species) had been probably the most adversely affected. That is most probably because of their very restricted foraging vary (100’s of metres, reasonably than kilometres).

’Protected’ colony densities

Within the conclusion of the paper the authors in brief speak about the honey bee ‘wearing capability’ of an atmosphere i.e. the choice of colonies that may be offered with out detrimentally affecting local bee populations.

This wearing capability will range in line with the floral assets to be had and – despite the fact that no longer mentioned – might not be consistent all through the season.

Overall pollen/nectar availability (blue line) varies all the way through the season . Expanding numbers of honey bees in an atmosphere (pink shaded house) successfully scale back what’s to be had. 

However it is a gross oversimplification … it assumes that each one floral assets are an identical. Generalists can exploit a lot of these assets.

Some bees are experts; rising, maturing, mating, laying and loss of life all the way through the flowering of a unmarried species or genus of crops (cyan line). If honey bees can use the similar useful resource, in particular if it vegetation when there’s a scarcity of different forage, it will critically prohibit what’s to be had for the specialist local bee.

MacInnes et al., cite two research which recommend that 3 or 3.5 hives according to km² is the precautionary really useful colony density that reduces damaging interspecies interactions (Steffan-Dewenter and Tscharntke, 2000; Torné-Noguera et al., 2016).

I’ve learn those two papers and neither are research of city bee populations – one is at the thyme- and rosemary-rich scrubland within the Garraf Herbal Park (Barcelona) , the opposite at the calcareous grasslands round Göttingen in Germany. Neither satisfied me that the steered 3-3.5 hives/km² had been based totally upon proof that essentially made them ‘transferrable’ to different environments.

However let’s suppose that they’re …

Environmental colony densities

The 2918 colonies in Montréal had been unfold erratically round 430 km² i.e. a colony density coming near 7 hives/km². Have in mind, there could have been undocumented hives that may building up this quantity.

I’m ignorant of significant to be had an identical knowledge on hive densities in the United Kingdom.

The Nationwide Bee Unit (NBU) stay a file of apiary and hive numbers of registered beekeepers (assuming data are up-to-date) however – irritatingly – most effective post the apiary numbers. Whilst you sign up an apiary you’ll be able to see the quantity however no longer location of different apiaries inside 10 km.

I’ve had apiaries the place the NBU “<10km apiary quantity” is as little as 1 (far flung west coast) or as top as 275 (Midlands). My present apiaries at the east coast have ~60 apiaries inside 10 km.

A circle of radius 10 km covers a space of 314 km² . Assuming you recognize the apiary numbers , what number of hives would there must be in each and every apiary to present a density of three or 3.5/km²?

Don’t believe my maths (!) however I believe the figures above are right kind.

My Midlands apiary, with 275 different apiaries inside 10 km would had been in a space with over 3.5 hives/km² if the opposite apiaries contained a mean of ~4 hives each and every. Primarily based upon my wanderings across the Warwickshire fields I’ve typically estimated that rural apiaries in fact reasonable ~5 hives each and every.

Take a look at your NBU Beebase-registered apiaries. What number of different apiaries are there inside 10 km? Do your bees forage in an atmosphere with hive numbers above or underneath 3.5/km² ?

How about city apiary and hive densities?

That is getting foolish …

I did a handy guide a rough test of apiary numbers in London, Cardiff, Glasgow and Edinburgh. Central places in Cardiff, Glasgow and Edinburgh had 196, 144 and 210 apiaries respectively inside 10 km.

Possibly wrongly I’ve at all times assumed that hive numbers according to apiary are much less in city than in rural places.

Persons are busy operating, gardens are small, balconies are cramped and who needs to hold 36 supers onto a flat roof?

If you happen to suppose there are 3 hives according to apiary in those towns then the hive densities are properly underneath the steered 3.5/km2 threshold.

However London is a distinct topic altogether.

I checked each outer and central London … each places I used to be acquainted with. Outer London had 441 apiaries inside 10 km and the central location I selected had an eye-watering 719 🙁 .

Except those apiaries comprise just one or two hives each and every it’s most probably that the three.5/km² hive threshold is exceeded.

If you’re an city beekeeper test the apiary numbers the place your hives are registered. There will probably be substantial geographic variation – even over fairly brief distances – relying what’s ‘in vary’.

Conclusions

As I’ve stated prior to, beekeepers have a duty to their bees and to the surroundings wherein we stay bees.

If we behave in some way this is destructive to the surroundings it’s going to, sooner or later, be destructive to our bees. However that egocentric justification shouldn’t be wanted … there will have to be no pride in swamping a space with hives if it leads to the lack of local bees and different pollinators.

It kind of feels as although this summer time has been deficient relating to honey yields … no longer in all places after all, however in lots of places. If our bees are suffering simply believe the have an effect on the presence of our colonies are having at the local pollinators that they proportion the surroundings with.

And take into account, the surroundings is being depleted, denuded and degraded; hedges are being grubbed out, box margins ploughed up, flower meadows transformed to silage manufacturing, insecticides are extensively used and local habitats are concreted over as city spaces extend.

It’s already difficult in the market for the masses of different bee species which our bees now compete with.

In terms of bettering pollinator numbers and variety, honey bees most definitely aren’t the answer … however they could properly be a part of the issue.

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Notes

For the ones of you who’ve coastal or lakeside apiaries understand that the NBU ’10 km radius’ most definitely isn’t sensible sufficient to take the water into consideration. One in every of my east coast apiaries has about 130 km² of North Sea inside 10 km, nearly all of which seems to be devoid of bees of any type 😉 .

I’m conscious about the deficiencies in my apiary/hive density calculations and can go back to this someday one day. If you happen to suppose honey bees forage 2 km from the apiary, a big apiary (e.g. a shared or affiliation apiary) containing 25 hives will lead to an area hive density of three.5/km². 

However, if apiary levels overlap and plant assets are erratically dispensed (which they’re) then a lot decrease hive numbers may lead to upper native hive densities. 

References

MacInnis, G., Normandin, E., and Ziter, C.D. (2023) Decline in wild bee species richness related to honey bee (Apis mellifera L.) abundance in an city ecosystem. PeerJ 11: e14699 https://peerj.com/articles/14699. Accessed June 6, 2023.

Normandin, É., Vereecken, N.J., Buddle, C.M., and Fournier, V. (2017) Taxonomic and useful trait variety of untamed bees in several city settings. PeerJ 5: e3051 https://peerj.com/articles/3051. Accessed August 17, 2023.

Smith, T.J., and Saunders, M.E. (2016) Honey bees: the queens of mass media, regardless of minority rule amongst insect pollinators. Insect Conservation and Range 9: 384–390 https://onlinelibrary.wiley.com/doi/abs/10.1111/icad.12178. Accessed August 16, 2023.

Steffan-Dewenter, I., and Tscharntke, T. (2000) Useful resource overlap and imaginable pageant between honey bees and wild bees in central Europe. Oecologia 122: 288–296 https://doi.org/10.1007/s004420050034. Accessed August 16, 2023.

Torné-Noguera, A., Rodrigo, A., Osorio, S., and Bosch, J. (2016) Collateral results of beekeeping: Affects on pollen-nectar assets and wild bee communities. Elementary and Implemented Ecology 17: 199–209 https://www.sciencedirect.com/science/article/pii/S1439179115001504. Accessed August 16, 2023.