Life Without Bumblebees? It's Not Just Honeybees That Are Mysteriously Dying

Bombus franklini, a North American bumblebee, was last seen on August 9, 2006. Professor Emeritus Robbin Thorp, an entomologist at UC Davis, was doing survey work on Mt. Ashland in Oregon when he saw a single worker on a flower, Sulphur eriogonum, near the Pacific Crest Trail. He had last seen the bee in 2003, roughly in the same area, where it had once been very common. "August ninth," Thorp says. "I've got that indelibly emblazoned in my mind."

Thorp had been keeping tabs on the species since the late 1960s. In 1998, the US Forest Service, the Fish and Wildlife Service, and the Bureau of Land Management supported an intensive monitoring project to determine whether the bee should be listed as an endangered species, in part because of its narrow endemism. The total range of B. franklini is only 190 miles north to south, from southern Oregon to northern California, and 70 miles east to west between the Coast and Sierra-Cascade Ranges.

When Thorp began to monitor the bee, populations were robust, and he even estimated their range to be slightly further to the north and southwest than previously believed. The study was, in part, an attempt to find out why franklini's range is so restricted and other western bumblebees, such as its close relative Bombus occidentalis, are not. Thorp was investigating that question when something else occurred: Populations of both bees began to decline precipitously. "All of a sudden the bees disappeared out from under me," he says.

Bees, and particularly the European honeybee, Apis mellifera, have come to symbolize a deepening ecological crisis in North America. Colony Collapse Disorder, first reported in 2006, has been described as "an insect version of AIDS," ravaging honeybee colonies throughout North America. It has become a cause célèbre of sorts, embraced by Häagen-Dazs, which features the bee on some of its pints of ice cream and asks consumers to imagine a world without pears, raspberries, and strawberries. In fact, the US has become so dependent on honeybees for agricultural purposes that in 2005, for the first time in 85 years, the US allowed for the importation of honeybees to meet pollination demands. Although millions of dollars have been invested in an effort to pinpoint the cause, the honeybee lobby and some environmental organizations say it's not enough, and argue that if dairy cows were disappearing, the response would be slightly more engaged.

The decline of bumblebees has received far less attention, though in the public imagination their plight has often been conflated with that of the honeybee. Not only do bumblebees pollinate about 15 percent of our food crops (valued at $3 billion), they also occupy a critical role as native pollinators. Plant pollinator interactions can be so specific and thus the loss of even one species carries with it potentially severe ecological consequences. As E. O. Wilson writes, "If the last pollinator species adapted to a plant is erased … the plant will soon follow." There are close to 50 bumblebee species in the United States and Canada that have evolved with various plants and flowers over the course of millions of years; our knowledge of those species, however, is incredibly weak.

In recent years, there has been much loose talk about the overall decline of pollinators, and the causes are manifold: habitat loss, pesticides, the spread of disease, and, without fail, global warming. The tendency to make sweeping claims about the demise of all pollinators has led to a lack of specificity when it comes to why particular species have declined, or in the case of B. franklini, disappeared. One of the only news stories to highlight the plight of bumblebees, published in The Washington Post last August, noted that "the causes of bumblebee decline are not scientifically defined and might be a combination of factors."

A crucial factor, according to Thorp and other scientists, was the rise of the commercial bumblebee rearing industry in the early 1990s, largely for greenhouse tomato pollination. Captive bees, they say, played a key role in spreading disease, which has led to the decline of several North American species, all of which belong to the same subgenus. If their theory proves to be correct, the rapid growth of the greenhouse tomato industry over the last two decades may have inadvertently wiped out a number of important native pollinators.