Bees fill a vital niche in the natural world, but are also essential to humans for the pollination of crops. Plants produce nectar to entice bees and other pollinators. Bees pursue the nectar of multiple plants and multiple species as food for themselves, while also gathering large quantities of pollen to feed their larvae. Bees carry the pollen from one plant to many others and thus cross-pollinate them.
Up to one third of crops grown for human consumption, including fruits, vegetables, nuts and spices, are dependent upon pollinators such as bees. Nearly 70% of all flowering plants are dependent on pollinators for reproduction. Pollinators are responsible for increasing the output of 87 of the most important food crops worldwide, a service valued at nearly $20 billion annually in North America alone. Under normal conditions, beekeepers expect up to a 20% loss of bees over the winter season, but losses are now between 30% and 60% on the west coast, and nearly 70% in Texas. While there has been a worldwide increase of 45% in managed honey bee hives, there has simultaneously been a 300% increase in the production of crops that rely on bee pollination.
Colony collapse disorder involves the disappearance of entire hives of honey bees. Thousands, even tens of thousands, of individual bees fly in pursuit of nectar and pollen, never to return to their hives. The factors most likely contributing to colony collapse disorder are habitat loss, pesticides, and diseases and parasites.
Following World War II, new farming methods resulted in a change from small family farms interspersed within a natural landscape that included woodlands, meadows and wetlands, to large-scale monocultures of wind-pollinated cereal crops. Crop rotations that included alfalfa and clover, which had both been reliable sources of pollen and nectar for pollinators, were replaced with inexpensive petroleum-based fertilizers. Monocultures are much more susceptible to disease and pests, so newly-developed pesticides and herbicides began to see wide-spread application. Not only do pesticides and herbicides eliminate pest insect species and competitive agricultural weeds, but also other insect species, including bees, and flowering sources of nectar and pollen on the edges of fields, road sides, and other rural lands. Where bee-pollinated crops remain, they provide a source of pollen and nectar for only a few short weeks, while the flowering plants that bees once relied on throughout the growing season have been eliminated.
Several Asian mites have been introduced to the United States. One species, Varroa destructor, can destroy a honey bee colony with 6 months to 2 years. Varroa destructor also transmits several deadly viruses among bees. As if that were not enough, a fungal parasite, also from Asia, known as Nosema ceranae, is also contributing to the decimation of bee colonies.
Colony collapse disorder is a combination of all these factors. Bees already weakened by disease or parasites are less able to survive poor nutrition from inadequate food sources and exposure to pesticides, and vice versa. Even sub-lethal doses of pesticides can decimate a colony. Common pesticides effect learning, foraging and the ability to navigate. The flowers, nesting sites and nesting materials within most rural as well as urban landscapes are contaminated with toxic pesticides. Changes in agricultural practices and an increasingly urbanized landscape have resulted in a severe reduction in the diversity of flowering plants, with not enough flowers blooming over the entire course of the growing season to sustain bee colonies.
Honey bees and native bee species populations have declined drastically. Read Bees…Part Two to learn what individuals can do to help.
Sources:
http://www.treehugger.com/clean-technology/where-did-the-bees-go.html
Stacy Arland
