Trouble for Wild Bumblebee
Bumblebees, those ace field hands that pollinate apple orchards, berry crops, tomato fields, wildflowers and flowering yard plants, are facing hard times in the United States. Nearly 10 percent of wild bumblebee species have suffered serious declines in numbers and geographic range, according to the first attempt at gauging the health of such populations nationwide.
Research surveying 78,000 specimens across eight species—and correlating reductions in numbers with potential causes—found that four of the species are in decline. Each had significantly lower genetic diversity than the four more robust species. This factor may make them more vulnerable to environmental stresses, including fragmented habitat and the intracellular parasite, Nosema bombi, sometimes present in high numbers in the troubled species.
The bees’ ranges have dropped by as much as 87 percent below their historically greatest extent, much of the decline occurring within the past 20 years. At the same time, the relative abundance of bees as compared with estimates of their known numerical peaks has plunged by as much as 96 percent.
Sydney Cameron, Ph.D., an entomologist at the University of Illinois at Urbana-Champaign, characterizes bumblebees as “incredibly resilient.” Yet, he remarks, “There’s a threshold, and above that threshold? Bang, that’s it. We just don’t know what the thresholds are for these species.” The study is considered an environmental warning and wake-up call.