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Bee-keeping in North America has also declined as bee-keepers suf- fered setbacks in recent years that threaten the long-term sustainabili- ty of a honey-bee-based pollination industry. Profitability declined as the US government pared away subsidies for honey producers.
Tracheal mites and varroa mites kill untold thousands of colonies annually and are expensive to control. Highly defensive Africanized bees may infiltrate bee stocks in parts of the continent and motivate bee-keepers to leave the business. It is perhaps no surprise that the number of bee-keepers in the US dropped by about 20% between 1990 and 1994 (Watanabe, 1994). It may become increasingly difficult to get enough honey bees to satisfy commercial pollination needs. This already seems to be the case in California almonds (Burnham, 1994), avocados (Mussen, 1994), in Florida citrus (Sanford, 1994), and in Washington orchard fruits (D.F. Mayer, personal observation).
In Europe, declines of bumble bees and other non-honey bees are documented in Britain (Williams, 1982, 1986), Lithuania (Monsevičius, 1995), Turkey (Özbek, 1995), Belgium and northern France (Rasmont, 1995), and parts of Poland (Ruszkowski and Biliński, 1995), although in western Poland the number of bee species remains virtually unchanged since the 1940s (Banaszak, 1992).
Populations of non-honey bees, whether natural or managed, are vulnerable to loss from many causes. Numbers and species diversity of bees are generally higher in natural vegetation than in disturbed agricultural areas, as shown in British Columbia (MacKenzie and Winston, 1984) and in Massachusetts (MacKenzie and Averill, 1995). Man’s activities destroy bee habitat and forage.
Vast monocultures of exotic crops, especially non-nectar-bearing cereals, can displace native bee forage. Pesticides applied to flower- ing plants, forest foliage, or bee nesting sites can reduce local popu- lations. For example, native bee populations in New Brunswick took three years to rebound after fenitrothion was applied on near- by woodland to control spruce budworm (Wood, 1979). Similarly, managed alkali bee (Nomia melanderi) populations in Washington took 3 years to rebound after an application of diazinon (D.F.
Mayer, personal observation).
Managed alfalfa leafcutting bees (M.rotundata) in the western US and Canada are attacked by fungi, predators, and insect parasites. A similar bee species, Megachite apicalis, does not prefer lucerne and sometimes takes over nests of the economically important M. rotunda- ta (Peterson et al., 1992). Fortunately, fumigation, sanitation, and insecticide-application procedures to control some of these diseases and pests are available (Goerzen and Watts, 1991; Mayer et al., 1991, 1992; Goerzen and Murrell, 1992; Goettel et al., 1993).
It is suggested that the exotic honey bee also may contribute to a decline of native non-honey bees (Buchmann and Nabhan, 1996).
Bee Conservation 25
Indeed, in the three centuries since its introduction to North America, honey bees have competed successfully with native pollinators for food resources. Honey bees excel at finding the richest nectar sources in a habitat which they then preemptively deplete, leaving behind less for non-honey bees (Ginsberg, 1983; Schaffer et al., 1983). It has been estimated that one honey bee colony can, in this manner, competitive- ly reduce the number of bumble bee queens and males produced within its foraging area by as much as 38,400 (Heinrich, 1979).
Nevertheless, it has proven difficult to empirically demonstrate a neg- ative environmental impact of introduced honey bees (see page 22).
Bumble bees occasionally are attracted to honey bee nests, and if they enter them they are often killed (Thoenes, 1993). A large number of these killed invaders are reproductive queens and males (Morse and Gary, 1961).
The perception of a bee shortage also may stem from a sharp worldwide increase in the area of bee-pollinated crops at the expense of cereals (Osborne et al., 1991). Even undisturbed healthy bee popu- lations may not be large enough for the enormous task an expanding human population now asks of them.
Clearly, it is in society’s best interest to maximize the number and diversity of our crop pollinators. This includes all bee pollinators, honey bee and non-honey bee alike. For honey bees, more research is needed to improve parasitic mite control, improve profitability, and contain costs of production. Honey bees are manageable, adaptable, prolific, and effective for many crops, benefits that cannot be dis- missed or marginalized. For non-honey bees, research is needed to understand basic life histories, develop or perfect culturing methods, and identify suitable food plants and nesting sites for conservation programmes. Finally, private and public granting agencies must recog- nize the importance of abundant pollinators and appropriately fund research and education programmes to that end.
Bee habitat conservation and improvement have received consid- erable attention in Europe, but relatively little in North America.
Conservation, however, is conceivably one of the most cost-effective ways to increase pollinators. The changes brought about by conserva- tion programmes, such as habitat sanctuaries and perennial bee pas- tures, tend to be long-lasting, spreading the cost of their installation over many years. Moreover, the benefits are long-lasting since perma- nent nesting sites and pastures encourage large, locally-recurring bee populations. In this chapter we highlight some of the principles and practices of bee conservation. Information given here was constructed largely in the context of conserving wild non-honey bees, but the practices recommended can indiscriminately benefit non-honey bees and honey bees alike.
26 Chapter 4