Since good pollination increases fruit yield and quality, farmers have long been interested in this phenomenon. The civilizations of the ancient Middle East understood, at least in a practical sense, the importance of pollination. A bas relief from Assyria dating around 1500 BC shows mythological creatures manually cross-pollinating date palms. The prophet Amos in the 8th century BC was a ‘piercer of sycamores’, a practice still done today in which poorlypollinated figs are manually gashed to induce ripening. Today, 90% of worldwide national per capita food supplies are contributed by 82 commodities that can be assigned to plant species and by 28 general commodities (such as hydrogenated oils) that cannot be assigned to particular species. Bees are pollinators for 63 (77%) of the 82 species commodities, and they are the most important known pollinator for at least 39 (48%) (Prescott-Allen and PrescottAllen, 1990; Buchmann and Nabhan, 1996). The multiplicative value of bee pollination becomes apparent when one tallies bee-pollinated food plants and considers the large quantities that are converted to animal feeds and ultimately meat, egg, and dairy products. One wellworn, and probably accurate, estimate says that one-third of the human diet can be traced directly, or indirectly, to bee pollination (McGregor, 1976). This estimate is probably more accurate for human diets in developed countries.
For fruit- or nut-bearing crops, pollination can be thought of as a grower’s last chance to increase yield. It is the degree and extent of pollination that dictates the maximum possible number of fruits. All post-pollination inputs, whether growth regulators, herbicides, fungicides, or insecticides, are generally designed not to increase yield but to conserve losses. Because of its yield-optimizing benefits, bee pollination can play an important role in maintaining a sustainable and profitable agriculture with minimized disruptions to the environment. Alterations in agricultural practices that significantly reduce yield rates have the danger of encouraging more wild lands to be converted into farmland to make up for reduced yields (Knutson et al., 1990). Good bee pollination and optimized crop yields are thus part of a sound environmental management policy.
Although wind-pollinated cereals make up the bulk of human diets, insect-pollinated crops often mean the difference between eating for survival or eating for pleasure. Insect pollinated crops are the delicacies one can easily take for granted. They are the low-acreage, high-value crops that pump millions of dollars into local agricultural economies. They are the forage plants that fuel livestock production. To gain an appreciation of bee pollination, one need only imagine life without beef steak, blueberry muffins, ice cream, pickles, apple dumplings, or watermelon. For many people in the world, such deprivations are not imaginary. If the gross disparities that exist in the world between rich and desperately poor, well-fed and not, are ever to be absolved, bee pollination will play a part. The area of bee-pollinated crops is increasing in many developed countries (Torchio, 1990a; Corbet et al., 1991). In Canada, over 17% of cultivated land is used for crops that depend entirely or in part on insect pollination (Richards, 1993). If developing countries follow suit, we can expect unprecedented growing demand for bee pollination in the 21st century.
The degree to which a particular crop needs insect pollination depends on the flower morphology, level of self-fertility exhibited by the plant, and arrangement of flowers on the plant or on neighbouring plants. Those crops are most dependent on insect pollination that have separate male and female flowers (so-called imperfect flowers), whether occurring on separate plants or on the same plant. In these cases insects, especially bees, are important pollen vectors, moving pollen from male to female flowers. There is a higher rate of self-pollination in plants with flowers housing both male and female sexual components (perfect flowers); however, bees often optimize pollination even in perfect flowers. Pollination in other crops, particularly the cereals, is accomplished by wind and gravity, and bees play only a minor role.
Finally, the economic value of bee pollination goes beyond production agriculture because bees pollinate more than just crop plants. All told, bees pollinate over 16% of the flowering plant species in the world (Buchmann and Nabhan, 1996). Bee pollination sustains native and introduced plants that control erosion, beautify human environments, and increase property values. Bees pollinate native plants which provide food for wildlife and have inherent value as members of local natural ecosystems. Although some believe that this generalization does not apply to the cosmopolitan honey bee, A. mellifera, which is an exotic species throughout most of its modern range, the bulk of experimental evidence suggests that introduced honey bees are only rarely a detrimental feature of local ecologies (Butz Huryn, 1997). In the absence of large-scale demonstrable negative impacts of introduced honey bees and considering their widely acknowledged value as pollinators of crop plants and their catholic plant preferences, it seems reasonable to anticipate that honey bees, even introduced populations, play an important role in sustaining natural plants and the animal communities that depend on them.
