Nearly one-third of the U.S. food supply requires the common honeybee, Apis mellifera, for pollination. These agricultural services add approximately $15 billion to the cost of food production within this country (Van Engelsdrop et al., 2008) and make a significant contribution to crop production. While there are other sources of animal pollination, also called biotic pollination, the honeybee pollinates about 130 different crops, including fruit, vegetables, and tree nuts within the United States. In fact, California almond production depends on about 1.3 million bee colonies, or nearly 50% of all honeybees in the United States (Southeast Farm Press, 2011).
Critical to our food supply is that 70% of tropical crops require at least one form of animal pollination. Nondependent crops are pollinated abiotically (e.g., wind) or autogamously (self-fertilization), and often reflect non-fruit components, such as leaves (e.g., tea, asparagus, Brussels sprouts, lettuce), stems (e.g., broccoli, cauliflower), and tubers (e.g., parsnips, potatoes, onions). Common pollinator-dependent crops include coffee, grapefruit, sunflowers, tomatoes, blueberries, and macadamia nuts; some important seed oil production depends upon the landscape and pollination variables. Thus, many animal pollinators, especially honeybees, represent a significant component in the ecosystem that benefits humans.
Estimates suggest there would be at least a 65% reduction in crop yield without these pollinators (Garibaldi et al., 2009), while others project a 3–8% decrease in total agricultural production (Aizen et al., 2009). Within the European community, some calculate that about 84% of the 264 crops depend on at least one form of animal pollination (Klein et al., 2007). Therefore, a pollinator shortage would have a significant impact on pollinator-dependent crops. For some crops, like almonds, pumpkins, watermelons, and some other melons, the reduction would be nearly 100%. Complete pollinator loss contributes to a reduced production of fruit such as strawberries, apples, and grapes (-12%) and vegetables such as melons (-6%) (Gallai et al., 2009). In the absence of the honeybee, ingredients like vanilla spice would require hand pollination management techniques.
The geographical distribution of this decline could have a significant impact in Africa, Asia, Europe, South and Central America, and North America. The global economic impact on nuts, fruit, edible oils, vegetables, pulses, spices, cereals, sugar crops, and roots and tubers could exceed 10% of the total production value of these foods or approximately $2.3 trillion.
One of the emerging threats to the global food supply is honeybee colony collapse disorder (CCD). There are many honeybee pathogens that affect colonies in different regions of the world (Genersch, 2010). Those pathogens include an array of viruses, bacteria, fungi, and parasites. With the advent of RNAi or RNA interference technology (Hunter, 2010), the growing evidence indicates CCD may depend on the ectoparasitic mite, Varroa destructor. Like the mosquito that can transfer the Plasmodium parasite responsible for malaria and the West Nile virus that leads to serious illness among avian species and humans, V. destructor may transmit virus(es) that lead to colony paralysis and ultimately colony death (Ratnieks and Carreck, 2010). In some regions of the world, this mite has been controlled through integrated pest management techniques. However, within the United States, the mite appears to be resistant to the introduction of acaricides and other miticides. Another pathogen that may be equally destructive to bee colonies is the parasite Nosema ceranae, which reduces food consumption by bees. This parasite has its origin in Spain and is now thriving in colonies of A. mellifera in many countries. However, the U.S. Colony Collapse Disorder Steering Committee (CCDSC, 2009) contends that CCD within the United States may not be associated with any known honeybee pathogen.
As we scan global agricultural practices and the apparent growing shortage of pollinators, the rate of pollinator-dependent crop planting exceeds the rate of nondependent crops both in the developed and developing worlds by at least 300% (Aizen et al., 2008; Aizen and Harder, 2009). This shortage not only stresses the environment, it represents another disruptor in the global food supply chain that has significant economic implications. This shortage may lead to alterations in some of our favorite nutritious foods recommended for consumption increase.
Can you imagine a world without fruit and vegetables? This may become a reality if scientists are unable to determine where all the bees have gone.
References cited in this column are available from the authors.
Roger Clemens, Dr.P.H.,
Contributing Editor
Chief Scientific Officer, ETHorn, La Mirada, Calif.
[email protected]
Peter Pressman, M.D.,
Contributing Editor
CDR, Medical Corps, U.S. Navy, Director Expeditionary Medicine, Task Force for Business & Stability Operations
[email protected]