Pollinators such as bees are essential for the reproduction of many plants, including flowers and some food crops, notes Claire Kremen, a conservation biologist at the University of California, Berkeley.
Pollination is the transfer of pollenplant grains that contain male DNAfrom the male part of a flower to the female part of a flower. This allows plants to reproduce.
Insects such as bees facilitate pollination as they buzz from plant to plant while feeding on nectar or collecting pollen.
Stunned at the decline in bee diversity, Biesmeijer and his team also compared plant diversity in the U.K. (United Kingdom photos and facts) and the Netherlands (Netherlands photos and facts) before and after 1980.
In Britain, where bee diversity has fallen and hoverflies have held steady, wildflowers that require insects for pollination have declined by 70 percent. Wind-pollinated and self-pollinated plants, on the other hand, have held constant or increased.
In the Netherlands, where bee diversity has fallen but hoverfly diversity has increased, there has been a decline in plants that specifically require bees for pollination but not in plants that make use of other insect pollinators.
The findings, according to Biesmeijer, suggest that the decline in bee and plant diversity is linked.
"We don't know whether it's from the plants declining first and then the bees, or whether the bees [decline], then the plants, or whether it's all part of a vicious cycle of extinction," he said.
The scientists hope further studies will determine the ultimate cause of the declines.
Researchers suspect a combination of habitat loss, pesticide use, and over-enrichment of water bodies with nutrients, often from fertilizers and sewage.
"Whatever the cause, the study provides a worrying suggestion that declines in some species may trigger a cascade of local extinctions amongst other associated species," Biesmeijer said in a media statement.
The loss of wild bee diversity is especially troubling against the backdrop of a well-documented decline in managed honeybee populations.
Farmers, especially in the U.S., have long relied on managed honeybees to pollinate their crops, but two parasites, the varroa and tracheal mites, have been slowly wiping out honeybee populations since the 1950s. (Related story: "Bee Decline May Spell End of Some Fruits, Vegetables" [October 5, 2004].)
"Basically, there are not enough managed bees around anymore to perform all these pollination services," Biesmeijer said.
The decline in bee diversity also has broad implications for human health and quality of life, adds the University of California's Kremen.
"For health, a lot of the fruits we eat do require animal pollinators or benefit from animal pollinators to provide more or larger fruita source of a lot of vitamins," she said.
"So for health, they are important."
As for quality of life?
"What would life be like without almonds in an Almond Joy?" she said, referring to the popular candy bar made with bee-pollinated nuts.
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