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.