U.S. bumble bees experiencing significant declines
Many U.S. bumble bee populations have declined significantly over the past few decades, with certain species dropping off by as much as 96 percent. While the decline is linked to low genetic diversity and disease, an underlying cause remains uncertain.
Scientists from multiple U.S. universities studied eight bumble bee species from across the country for three years, paying special attention to changes in their distributions, genetic diversity, and infection rates. Their report, published in the Proceedings of the National Academy of Sciences, is the first to comprehensively survey bumble bee populations in the U.S.
Bumble bees are important pollinators worldwide. Many wild ecosystems rely on bumble bees to ferry pollen from one flower to another. Their robust size, long tongues, and buzz-pollination method (high-frequency buzzing which encourages flowers to release their pollen), also make them highly efficient pollinators of crops.
Reports in Europe preceded those in the U.S. Of 19 species of true European bumble bees, three are locally extinct and eight are in serious decline, leaving only four widespread species in the entire region. Habitat loss, climate change, and pathogenic infection are thought to contribute to European declines.
The U.S. team, led by University of Illinois entomologist Sydney Cameron, compiled a database of more than 73,000 museum records and compared them to current population assessments determined through intensive surveys of more than 16,000 specimens at 400 sites. The study was the first national large-scale survey of bumble bee population health and found that four of the eight species studied had declined by as much as 96 percent, and that their ranges had shrunk by 23-87 percent.
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