How many bees fit in a city?

I get crucified every time I question the practice of urban beekeeping. Still, I think it’s important to examine the issues. Today I’m thinking about the carrying capacity of the urban landscape. And by urban, I mean big cities—places like Toronto, Sydney, Chicago, London, Los Angeles—not suburbs.

Biology Online defines carrying capacity as “the largest number of individuals of a particular species that can survive over long periods of time in a given environment.” That number will depend on limiting factors that may or may not be obvious.

There is no disputing the fact that urban beekeepers have kept healthy hives on rooftops and balconies for years. The bees thrived and salable crops of honey were produced. But what happens as beekeeping rises in popularity and urban beekeeping becomes legal? How many hives can you stack atop tall buildings before the bees begin to starve?

The most obvious limiting factor in the urban landscape is the number of nectar-producing flowers. So far, the urban bees have done well: they work tirelessly, fly many miles, and fill up their combs with city gold. But can these environments support twice as many colonies? Maybe. What about four times as many? We don’t know, but at some point we will reach a line that can’t be crossed.

Think about it this way: you can only put so many cows in a pasture or so many fish in a pond before they will starve. “But,” you say, “bees are free. Not fenced or caged or penned, they can go anywhere they want.” While this is true, there are only so many hours in a day, so many miles they can fly before they simply wear themselves out.

Consider this. In the 1960s certain jurisdictions in the northeastern U.S. severely limited deer hunting. At first the laws produced the desired effect and the deer population skyrocketed. But later there were so many deer that they began dying of starvation. Like bees they were free to go where they wanted, but the woodlands and meadows had exceeded the carrying capacity for deer . . . so each deer found a little less food than it needed to survive.

I wonder if an urban bee works harder for a living than a suburban bee. We know that in times of dearth, honey bees will forage unreasonable distances. By that I mean they will fly so far that the food energy they collect is about equal to the calories burned to collect it—a practice that hurts the colony.

And here’s another thought. Honey bees are known for floral fidelity. That is, they are programmed to spend an entire foraging trip or an entire day on one species of flower. So what does an urban bee do when she can’t find large patches of a single variety? Does she fly ever further looking for it? Does she settle for a mixture? Does she return to her hive with a partial load? How does this affect her efficiency?

In a natural situation the colonies would swarm into a less populous area. But a good urban beekeeper, out of consideration for others, must keep his bees from swarming. So perhaps he runs even bigger colonies or splits them into more hives. The result only makes the problem worse—more bees in the same geographical area.

Is it fair to put honey bees where patches of green and blue and yellow are so very far apart? I’ve been told the answer is to plant more flowers. I love the idea of flowers in the city, but how many flowers does it take to support even one more hive? How many millions and millions? It’s a great idea but the numbers don’t work—not when the hive count is exploding.

I am not condemning a particular beekeeper, city, or method. I am only hypothesizing that as urban beekeeping gets ever more popular, the number of colonies will reach an asymptote—a population where survivability levels off and only the most strategically placed hives prevail. After a number of frustrating years urban beekeeping will wane. When the number of colonies falls to pre-boom levels, the remaining colonies will once again be able to thrive.

Rusty
HoneyBeeSuite

Overlooking the city. Flickr photo by Your Secret Admiral.
Overlooking the city. Flickr photo by Your Secret Admiral.

Comments

Herb
Reply

Rusty… I wonder if our Urban Beekeepers in China have experienced this problem….I understand their government pays their BEEKEEPERS to produce and establish hives.

Roger
Reply

I agree with your concern, however, I see one weakness in your logic. There seemingly is not a problem now since urban bees seem to be thriving at least in many cities thus suggesting that they are experiencing none of the stresses which might indicate an approach toward their carrying capacity. However, twice, you mention possible future concerns as urban beekeeping becomes more popular. You seem to suggest that this change in popularity will happen in a vacuum with no accompanying changes in urban life. I personally think that any increase in urban beekeeping will likely occur together with overall movements toward might be called ‘urban farming’ with many more roof top gardens and increased greenery in the landscape as a whole. Thus, it is not simply a question of planting more flowers for the sake of flowers but a change in outlook which involves BOTH urban beekeeping AND increased numbers and abundance of nectar and pollen sources in the cities.

Emily
Reply

Hi Roger,

Some beekeepers I know in London feel there is a problem of too many bees and not enough flowers right now.

Urban beekeeping has risen in popularity but planting flowers has not! Sadly the reverse seems to be happening and many people are turning their front gardens into car parks (road parking space is very tight here, no garages). Another pressure is that people work long hours and have long commutes here. Perhaps as a result of this, Londoners feel they don’t have time for gardening, which may explain the trend towards decking/gravel in back gardens.

Rusty
Reply

Based on past spikes in beekeeping popularity, they don’t seem to last very long. My prediction is that this one will peak and start to decline again before many changes are made in urban greenery. Even now, as some people put in gardens and trees, others are busy taking them out and paving them over. I don’t think the net difference well be great.

It would be nice if I am wrong . . . I hope so.

Gretchen
Reply

I would suggest that the solution is not to plant more flowers, but more trees. Most people think of those lovely “bee forage wildflower” mixes to feed bees, and while it may provide a small snack, most patches aren’t enough. But what about large flowering trees and large pollen producing trees? I am thinking along the lines of what Kim Flottum talks about in terms of the 3-D bee forage landscape (can’t remember his terminology). If you keep a bee hive, be committed to plant xx number of diverse bee forage trees.

Your question makes a lot of sense to me. Even with living in the midst of great bee forage habitat, I am thinking of ways to provide more in case my number of colonies increases, particularly in the shoulder seasons. When you are talking trees, you need to think at least a few years in advance.

Rusty
Reply

That’s an excellent point; one tree can feed a lot of bees.

Gretchen
Reply

And by planting more trees, I don’t necessarily mean on your own property. Neighbors, parks, guerrilla planting…

Rusty
Reply

And of course flowering trees have all those other qualities. They provide shade, dust filtering, noise reduction, privacy, wind protection, reduce the need for air conditioning, provide bird habitat, produce leaf mulch, reduce surface run-off, aerate soil. . . I’ve read they can even reduce crime rates. I can’t imagine a place in the world that wouldn’t benefit from another tree–with bees or not.

Emily
Reply

I agree with what you’re saying. The answer to helping bees in London isn’t getting everyone here to be beekeepers. Once you hit saturation point you just have more bees bringing home less nectar each, which must result in weaker colonies. And the wild bumbles and solitary bees need some flowers too.

Having said that some areas of London, even in the centre, are pretty green. We have quite a few parks with flowering trees which provide large patches of one flower species. Regents Park, which I work near, is too large to walk around in my hour long lunch break. And trees are often planted down the sides of roads in the outer boroughs. I suspect it’s these trees which the bees rely on rather than the little patches of flowers found in gardens.

Rusty
Reply

Another vote for trees . . . and yes, I agree. Central Park in New York City is also very large and very green.

Emily
Reply

Trees rock. I love all the pink cherry blossom out now.

Sergey
Reply

I just read somewhere that in 1887 Los Angeles had 100 thousand beehives, yes! I think, we have space to grow keeping in mind all bees problems… I agree that saturation point is very serious issue for urban beekeeping. I was very concern on food availability when established my bees, but reality is that my bees foraged on ivy, than on eucalyptus and now on citrus. Hopefully, they will continue finding the food. I agree with author above that flowering trees may help tremendously. I also observed fantastic plasticity in urban bees – it seems to me, they could adapt to many difficult conditions. There is a phenomena in fish aquarium: if you put just a few fishes into large aquarium, they will grow very big. If you put many fishes in the same aquarium and provide unlimited food – fishes will be much smaller than in the first case – mother nature has her own ways. Something like that may happens in the urban environment – may be bee colonies became smaller… Also, in urban conditions, bees may need less honey for overwintering (warming etc).

Dennis Law
Reply

New York City has an organization with plans to plant a million trees.
http://www.milliontreesnyc.org/html/home/home.shtml

I understand that they have recently agreed to STOP planting the useless-to-bees Callery or Bradford pear trees.

I’ve noticed there are many abandoned construction sites and foreclosed properties that could use a few seeds tossed over the fence.

I’ve recently acquired some seeds for the Korean Evodia (Tetradium daniellii) or Bee Tree
and I have lots of left over sunflower seeds from last year’s garden…

Rusty
Reply

Good work. We should all join in the tree planting effort.

M.S. Patterson
Reply

I’m not sure what you mean by “useless to bees” with these pears. They flower heavily, and are visited by various bees species (like most members of the Rose family).

The main reason these trees are no longer being planted is because there is now sufficient genetic diversity within easy pollinating distance that they are able to reproduce (they can’t self pollinate), and they are quite aggressive spreaders. Personally I think they are crap trees for anything but flowers (and even those stink). But Pyrus calleryana could not become invasive without assistance from pollinators like bees.

http://mipn.org/Callery%20pear.pdf

Rusty
Reply

I’m no expert on pear trees, but if I remember from ag school, pear trees in general are not preferred by honey bees because their nectar is low in sugars compared to other things that may be in bloom at the same time. Honey bees prefer nectar that is very high in sugar because it is easier to make honey. Many native bees are just fine with pear nectar as they use it for food, not for honey.

So to say that pear nectar is useless to bees is not exactly accurate. Truthfully, I have pear trees that I’ve never seen a honey bee go near, but they buzz with the activity of other bees. That said, if there is a dearth of other nectars, honey bees will forage from the pear trees and, in that case, they are certainly not useless to honey bees but may prevent them from starving.

Sarah
Reply

I wondered why my bees were not on the pear trees in the neighbor’s yard, good to know. I recently identified these three trees in my yard as choke cherry trees. They are in full bloom but smell awful (like bitter almond) and all parts of the tree except the fleshy part around the seed contain cyanide. The butterflies love them, though.

Summer
Reply

Howdy! I’m an Urban Beekeeper in L.A. and while I get your argument, I’d like to point out a few things. First off, let me start by saying these points are specific to Los Angeles, as I am not as familiar with the landscape of other cities, and I’m a Backwards Beekeeper, so I’ll be speaking from experience in the organic/sans treatment camp that gets all their bees from rescues of feral bees in the area via swarm pickups or cut-outs:

1. Los Angeles is SUPER green. There are tons of hidden gems of gardens, hillsides, parks, and other flora that flourish. Ours may be a sprawling concrete jungle, but it has more than a few oases of green.
2. The popularity is not growing spectacularly. Are there a lot more beekeepers here than there were? YES! However, as part of our outreach team for education, I find the majority of people are interested in supporting beekeeping and a much smaller population actually wants to have a hive of their own.
3. Our wild hives are flourishing to such an extent, we can’t keep up with swarm rescue calls and cut-out requests that we currently receive! According to the County of L.A., there are up to 9 feral hives within every square mile of the county – these are unmanaged, wild hives. I can attest to at least 4 wild hives being present within a 5 minute walk of each other along the bank of the L.A. river alone. This means that the wild hives are not having problems with finding forage even as the number of managed hives goes up every week.
4. It’s still not legal here. I’m working very hard to legalize beekeeping for residents zoned R1 within the City of Los Angeles. However, currently only Agriculturally zoned properties may have bees. Part of the legalization efforts include “reasonable restrictions” for urban beekeeping which includes limiting hives to 2 per beekeeper. With beekeepers spread out through different neighborhoods in the sprawling entity that is L.A., I do not see over-saturation of hives becoming an issue for a very long time.

I think, in L.A. at least, that the city is spread out enough into areas that are still wild and wooly that bees competing for limited forage will not be a problem for the foreseeable future. This may not be the case, however, in other areas that are not as amenable to year-round gardening and do not have the mild, warm climate that Southern California prides itself on.

Phillip
Reply

I respect what the Backwards Beekeepers are trying to do, but L.A. beekeepers have it so easy compared to most cold-climate beekeepers, it’s kind of ridiculous.

I was going to chime in earlier that much of the carrying capacity of a city is climate dependent. A warm climate like southern California is a whole other world compared to where I live.

I live in a very small city in a cold, wet climate. I’m not sure how many honey bee colonies could be supported here, but if urban beekeeping became popular, carrying capacity would be a valid concern.

As usual, all beekeeping is local beekeeping.

Summer
Reply

Yes, we do have it much easier. We always say to new beekeepers – Don’t worry. You might make a mistake that kills your hive, they might swarm, they might abscond – but there are always more free bees to be had. We say this not to be cavalier, but because it’s true. There are so many bees down here that I have at least 10 emails in my box right now for calls just from this morning – people have swarms and hives they want out of their yards and houses.

I always wonder when people say the feral population has dwindled significantly – because here it def. hasn’t. I guess we’re a little spoiled!

Rusty
Reply

How do you know that all those swarms and hives that people “want out of their yards and houses” are not escapees from California’s vast agricultural areas? Or if not from there, from all those LA beekeepers that “don’t worry” when their hives are swarming and absconding? Certainly they’re going somewhere.

I do not believe for one minute that you are seeing truly feral bees. You are seeing bees that have escaped from managed hives in the past one to two years. With millions of hives being moved in and out of California every February, there are going to scads of swarms. Much research into the decline of feral hives has come from UC Davis and those people are telling us that the truly feral colonies–ones that have lived many years in the wild–are nearly non-existent.

Feral does not simply mean “on the loose” or “running from the neighbor’s farm.” It means having returned to the wild state.

Summer
Reply

Hi Rusty,

The bees I’ve been collecting are small-cell bees. The bees themselves are very tiny. The millions of hives being moved in and out of California are moved into the Central Valley, between Los Angeles and San Francisco, way north of where I am. I have removed hives that have been there anywhere from a few months to several years to 20+ years. There are tons of old stucco buildings falling apart all over L.A., allowing incredible habitats for bees to hang out for decades without being interrupted.

I’m not seeing much varroa in these feral bees. It’s just not there. I don’t think it’s a problem for them. I also don’t have it in my hives, and I don’t treat at all for it. How long do bees have to be loose for them to be considered “returned to the wild state”? I think having them be loose long enough to regress to small-size should count!

The LA Beekeepers that “don’t worry” are far and few. I said we tell newbees not to worry when they make mistakes because it makes them calmer and more confident. Truth is, we practice open brood nest management and do our best to keep bees from swarming, as it is considered better beekeeping in urban environments.

Sergey
Reply

Rusty
Los Angeles Metropolitan area is approximately 100 miles in diameter (very rough approximation). Closest to us agricultural area – “central valley” is more than n 200 miles away trough mountains. So, it is very unlikely that we have bees originated from “pollination” bees delivered to the Central Valley every February from other states. In this sense, LA is special,I guess… My bees spent at least two years in very “feral” condition – they lived in semi-disintegrated boxes without frames etc. As a matter of fact, they made a roof out of leafs cemented by wax and propolis… Now, they are for 7-8 months with me in much nicer environment (I am not sure if they really liked the change). Roughly, they do exist for 3 years and they were quite “feral”. They made 30 kg honey so far for me and 6 (sic!) mediums tall at the moment… I think, such colony is very precious because they are survivors. I do not think that European immigrant bees may be truly “feral” in America. Nevertheless, there is evidence that they are doing pretty well without human interference – I saw beautiful honey bees in the Red Canyon last fall – in desert.
I have tremendous respect to Backwards Beekeepers. I am planning to join this organization.

M.S. Patterson
Reply

My main concern on this front is not for the honey bees, which after all are a domesticated species and foreign invaders here in North America, but for the remaining native bee populations that make use of urban areas. Various studies have shown that a quite large number of native bee species dwell, forage and reproduce in urban environments. Every hive of honey bees added to the urban environment increases the competition for pollen and nectar resources with those native species, and increases the possibility of spreading pathogens to natives.

I know that native bees do not produce the honey and wax like A. mellifera, but I would encourage people to create habitat for native bees in their gardens, yards, and rooftops. I’ve been quite pleased to see that you’ve had a number of posts on the subject.

Rusty
Reply

I agree that native bees are the ones most hurt by a large population of a foreign species in an area with limited resources. Most natives do not have a forage range that even comes close to that of a honey bee, so any urban native bees in close proximity to honey bees will be in a fight for their lives.

Politically I am a strong believer in individual rights, so I believe urban dwellers should be allowed to keep bees. But as with any other right, it can only extend to the point where it doesn’t infringe on the rights of others. With beekeeping this is true not only of human health and safety but also to the health and safety of non-human populations–in this case native bees. If we want a healthy environment, we need to wake up to what we are doing to other species, both plant and animal.

Nancy
Reply

>> useless-to-bees Callery or Bradford pear tree.

I did not know those were no good for bees. In Cincinnati, 50 miles north of here, they are invading expressway embankments!

Luckily we have lots of black locust around here, so my 4 “guest” hives have plenty to do. Their suburban keepers decided to limit their yard to two hives, and place the other 7 (some are nucs) here, after they saw all my locust, clover & goldenrod.

We are also plagued with Amur honeysuckle, but at least the bees (and goats!) like it. I will spread the word about Bradford pear.

geordy Mark
Reply

I’m an urban beekeeper in London and professional ecologist/nature conservationist. I agree there is a problem with too many bees in our city. Whilst London has many green and leafy tree-lined streets and parks, most are planted with London planes which offer zero forage for bees. In fact they are absolutely useless for biodiversity altogether. Most of our urban parks are a mixture of plane trees and amenity grass which is mowed so short that clover, dandelions and daisies don’t get a look in.

Where there are swaths of color in our parks they are more often than not highly bred, showy hybrids and bedding plants grown for their colorful displays and not for their nectar and pollen producing abilities. Most bedding plants such as bizzy lizzy, geranium, and begonias are useless to bees … and any other pollinators for that matter.

In some parts of London we have up to 150 honey bee hives per km2. This is more than 140 times the natural colony density for wild bees, and still hugely more than the average density per km2 of hives kept in the wider countryside where at times of the year bees have access to huge fields of forage.

I think we have reached a ceiling with the number of hives we now have in London. In short we have too many hives, not enough quality forage, far too many poorly or untrained altogether beekeepers and you will be hard pushed to meet a beekeeper right now who won’t tell you that their honey crops are going down in recent years. I know one beekeeper with several hives in a very green and leafy part of town who is an accomplished keeper of bees but who struggles to harvest any honey from their hives and strongly believes it’s because there is just too much competition from neighboring beekeepers.

*We need more people planting open-pollinated flowers in their gardens, window boxes and hanging baskets instead of crap annual bedding types
*We need more existing beekeepers brushing up on what they think they know about bee husbandry and attending training courses
*We need parks managers to leave more areas to grow longer and allow wild flowers back in rather than endless oceans of amenity grass mown within an inch of its life
* We need more native trees in our city’s streets, parks and gardens instead of worthless plane tree and non-native limes which are toxic to bees
*More green roofs to create forage opportunities

Rusty
Reply

Mark,

Thank you. This is more or less what I suspect is the case in many urban beekeeping areas.

Emily
Reply

Hi Mark,

Now that you mention it, I have seen London plane trees everywhere here – just looked up what they look like! Sad that they’re useless for bees.

I live in Ealing and think I might know the accomplished beekeeper you’re referring to. I’m trying to do my best to improve my beekeeping skills by attending the bee inspector training days at Roots & Shoots and also taking BBKA exams.

Wonder if the BBKA could have a role to play in lobbying local councils to improve bee-friendly planting. We need to start treating this as a national priority. It doesn’t cost anything to let the grass grow a little bit! Beekeepers will always look after honey bees but I’m especially worried about the solitary and bumbles, who must be struggling in all this endless rain.

Liz
Reply

Everyone loves it when individuals come together and share thoughts. Great blog, stick with it!

LondonPlanters.co.uk
Reply

London is filled with concrete, not with trees and flowers. Even if there is demand for planting and flowering in the city, still hard to find more flowers and plants for better eye-treat. But, if you check out certain places, specially Zone 1 – the city of London, you might have noticed the buildings are still decorated with beautiful flowers within Window box – how about the office buildings around Liverpool street?

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