As humans have known for millennia, and as many authors have reminded us, city life is hard–but it has some advantages. The same turns out to be true for bees, who suffer from a higher rate of parasites in urban environments, but pollinate more plants than they do in agricultural areas.
First off, the parasites in question are common; normal parasites that are part of bee’s lives, and not something unexpected. The rates of parasites in urban bees are higher compared to rural bees, but they may not be higher per se. Modern agriculture isn’t all that great a place for bees, since flowering plants are far less common on farms, leaving them with less to do. Subsequently, they might have fewer parasites there because agriculture changes frequently, and has done so very rapidly in the last century, perhaps faster than the parasite-pollinator-plant ecosystem can adapt.
Meanwhile, when people plant in urban areas, they often focus on flowers, or flowering trees, in an effort to beautify otherwise drab cities. With more flowers come more bees, who are likely living in something more accurately approximating the environments they evolved to inhabit. This is not to say that bees only thrive in cities. Flowery meadows, orchards full of flowering trees, or other “wilder” areas can still support bees pretty well–it’s just that plants like corn don’t offer them a lot of pollination options.
Because bees can’t quite keep up with the rate of change in agricultural areas, they aren’t as able to support hives and nests, which may be one factor in the decline of bees around the world. In our search to understand and combat colony collapse disorder and save the bees, we’ve looked for a lot of different culprits, from cell phones to pesticides, but we may need to pay more attention to something more fundamental: food supply.