Research Reviews
Can our high colony losses be blamed on intensive agricultural practices?
Answer: When compared to Latin American countries, quite possibly.
Honey bees are ecological generalists. This means that they are not tied to a specific food resource, nesting place, or geographic area. Nature is full of ecological specialists, those that are constrained by such factors: diseases that only infect particular populations, cicadas that only emerge once every 17 years to avoid major predators, microscopic mites that live on your eyelashes, the list goes on. Generalists, on the other hand, are able to adapt to changes in their environment, to different circumstances, and to many other challenges that they might face.
It is in fact this ecological plasticity that makes honey bees so remarkably adept. Being able to forage on almost any flower within a 3 mile radius—a total area of almost 50 square miles—certainly has its advantages! They can also nest in a variety of places, from hollowed trees to grandma's attic. Indeed, it is precisely because they are generalists in their foraging and nesting habits that makes them ideally suited for agriculture. Moving hives from one crop to another doesn't really phase them, since they can pick up in their new location where they left off. Try that with other bees!
But because honey bees are so amenable to commercial production agriculture and the pollination requirements of so many crops, it does expose the greater honey bee population to many special conditions that are unique to agroecosystems. First, and perhaps most obviously, are the multitude of chemical pesticides that are routinely used in most agricultural systems. Some are highly toxic to bees, others are less so, but clearly their repeated and prolonged exposure can be quite negative for bees. Second, with increasing acreages in our agricultural practices, honey bee colonies are often placed into areas that contain nothing else besides the target crop. While this helps to fulfill the purpose of using bees in the first place (pollination), it does bring with it a potentially significant downside in the lack of diverse food sources. Just as if we were to eat the same thing day-in day-out for a protracted period of time, the honey bee diet requires diversity in its nectar and pollen for long-term health. Third, because our bees are managed by beekeepers, they are less at risk to natural selection. This means that they are less likely to adapt over time to changes in the environment, agricultural or otherwise.
With the widespread and ongoing die-offs of honey bees worldwide, there has been a clamor of discussion about what is to blame and why. As yet, no single factor has emerged as the leading culprit, although speculation abounds. One way to perhaps clarify the situation is to take a step back and take a larger view of the honey bee population in different parts of the world. This is precisely what a group of researchers from Mexico and Argentina have done in a recent paper in Apidologie as part of a special issue on bee health.
The authors main premise is that there are relatively fewer honey bee colonies dying off in Latin America than in Europe and North America. The authors admit that data is scant and record keeping is inconsistent across the region, and they also cite many examples of unusual colony mortality. However, these instances are almost always associated with intensive agricultural practices. They then go on to posit several other factors that are special to—if not unique of—Latin American apiculture. First, the overwhelmingly predominant type of honey bee is the Africanized honey bee (AHB). This has two important consequences: (1) the AHB is not artificially selected but is rather subject to natural selection to overcome diseases and other maladies, and (2) they have maintained a greater population-wide genetic diversity because they are not actively bred. Second, the authors cite how the preserved natural vegetation and pollen diversity in South America is much higher compared to the US and Europe. This means that bees are able to acquire a greater diversity of food sources. Finally, the authors argue that Latin America still holds to small-scale agriculture that uses lower levels of synthetic pesticides, which may also help explain why those bees are more healthy.
In all, there are many different aspects acting in concert that are responsible for colony ill-health, and many of them are associated with large-scale and intensive agricultural practices. Whether or not these issues significantly impact our bees on a finer scale is subject to intense debate and will require hard empirical evidence to support. But it is clear that taking such a top-down approach to addressing these heavy issues can be helpful to inform the entire debate.
Reference
Vandame, R. and M. A. Palacio. (2010). Preserved honey bee health in Latin America: a fragile equilibrium due to low-intensity agriculture and beekeeping? Apidologie, 41: 243-255.
