WASHINGTON – Long-term population trends for some North American pollinators – bees, birds, bats, and other animals and insects that spread pollen so plant fertilization can occur – are “demonstrably downward,” says a new report from the National Research Council.
However, there is little or no population data for many pollinators, which prompted the committee that wrote the report to call for stepped-up efforts to monitor these creatures and improve understanding of their basic ecology.
Critical critters. In order to bear fruit, three-quarters of all flowering plants – including most food crops and some that provide fiber, drugs, and fuel – rely on pollinators for fertilization, and farmers often lease thousands of colonies of bees to ensure pollination.
Research indicates that shortages of pollinators for agriculture already exist and that decreases in wild pollinator populations could disrupt ecosystems in the future.
Big impact. “Despite its apparent lack of marquee appeal, a decline in pollinator populations is one form of global change that actually has credible potential to alter the shape and structure of terrestrial ecosystems,” said committee chair May R. Berenbaum, with the entomology department at the University of Illinois.
The report notes that much more data have been gathered on pollinators in Europe, where researchers have definitively documented declines and even extinction. Nevertheless, there was sufficient evidence for the committee to conclude that some North American species are in decline, especially the honeybee.
Bless the bees. Honeybees are crucial to agriculture, pollinating more than 90 commercially grown crops.
For example, it takes about 1.4 million colonies of honeybees to pollinate 550,000 acres of almond trees in California.
Studies show that U.S. honeybee populations have dropped since the 1980s, when a non-native parasitic mite was introduced, although the full extent of the decline is unclear because of problems with the way the federal government collects statistics on the beekeeping industry.
Step up survey. The report calls on the USDA to improve its methods for surveying honeybee populations, and do so on a yearly basis.
The shortage is significant enough, however, that honeybees had to be imported from outside North America last year for the first time since 1922, when the Honeybee Act banned such imports for fear they would introduce non-native pests.
Such fears are still justified, the committee warned, recommending that USDA and relevant agencies in Canada and Mexico take steps to prevent the introduction of new pests, parasites, and pathogens if bees are imported.
Antibiotic-resistant pathogens and encroachment by Africanized honeybees also are hurting North American honeybee levels, the committee noted.
Other species. Long-term trends for several wild bee species – especially bumblebees – as well as some butterflies, bats, and hummingbirds also show population drops, the committee found.
The causes of decline in wild pollinators vary by species and are difficult to determine.
Like the honeybee, the bumblebee has been hurt by the introduction of a non-native parasite. Many pollinator declines are associated with habitat loss, although U.S. data often are inadequate to link the two definitively; one exception is the drop in the bat population, which can be attributed to destruction of cave roosts.
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