and the Bees
Pollinator Populations Need to Be
Three-quarters of all flowering plants rely on another organism to perform a critical step in their life cycle: pollination. In fact, about one-third of the world's food supply comes from crops that depend on bees, birds, bats, or other creatures to carry pollen to complete the fertilization process. When there are not enough wild pollinators in the area, farmers often lease thousands of colonies of bees to do the job.
In recent years, however, there have been reported shortages in the number of pollinators available for agriculture, and studies showing a population decline in certain pollinator species have prompted concerns that ecosystems could be disrupted. To raise awareness of this issue, the North American Pollinator Protection Campaign, representing dozens of agencies and organizations in Canada, the United States, and Mexico, was formed. As part of its efforts, NAPPC requested that a National Research Council committee assess the status of pollinators on this continent.
The committee quickly discovered that data on North American pollinators paled in comparison to the information that has been gathered in Europe, where researchers have definitively documented declines and even extinctions. Nevertheless, enough data existed for the committee to find "demonstrably downward" population trends in some North American pollinators.
The evidence of a decline is most compelling for the honeybee, which is widely used for pollination; about 1.4 million colonies are needed to pollinate 550,000 acres of almond trees each year in California, for example. The number of honeybees in the U.S. is dropping, in part because of the toll taken by the non-indigenous varroa mite, a parasite first discovered in America in the 1980s and one that has proved stubbornly resistant to pesticides. To gain a better understanding of the extent of the honeybee decline, the U.S. Department of Agriculture's National Agricultural Statistics Service needs to collect more accurate data from the beekeeping industry, the committee said.
The shortage of honeybees is severe enough that last year it forced almond growers to import honeybees from outside North America for the first time since 1922, when the Honeybee Act banned such imports for fear they may introduce non-native pests and pathogens. Such fears should still be a concern, the committee warned, and USDA should support research to develop new pest-management and bee-breeding practices.
Among wild pollinators in North America, there is evidence of a drop in the abundance of several types of wild bees, especially bumblebees, as well as some butterflies, bats, and hummingbirds. But for most pollinator species, a lack of long-term population data makes assessments exceedingly difficult. A shortage of taxonomic resources and an incomplete biological characterization of most pollinator species further complicates efforts to catalog their numbers and diversity. The committee recommended that the United States, Canada, and Mexico establish a pollinator-monitoring network, beginning with a rapid, one-time assessment that can be used as a baseline for future comparisons.
The reasons for wild pollinator declines are not well-understood, although habitat degradation and loss have played a role, and climate change may be a factor as well. The bumblebee, like the honeybee, has suffered because of a recently introduced non-native parasite. The consequences of these declines in non-agricultural settings are not well-understood either. Few plants rely on a single pollinator, but rare and endangered plant species may be more vulnerable to extinction.
Too little is known about the basic taxonomy and ecology of most pollinators to design large-scale conservation and restoration programs at this point, the committee determined. But there are some simple steps that people can take on their own, such as planting native flowers to enhance pollinator habitat. -- Bill Kearney
Status of Pollinators in North America. Committee on the Status of Pollinators in North America, Board on Life Sciences and Board on Agriculture and Natural Resources, Division on Earth and Life Studies (2006, approx. 396 pp.; ISBN 0-309-10289-8; available from the National Academies Press, tel. 1-800-624-6242; $56.00 plus $4.50 shipping for single copies).
The committee was chaired by May Berenbaum, Swanlund Professor and head, department of entomology, University of Illinois, Urbana-Champaign. The study was funded by the U.S. Department of Agriculture, U.S. Geological Survey, and the National Academies.