Rusty Patched Bumble Bee Threatened with Extinction

The Xerces Society for Invertebrate Conservation filed a petition today with the U.S. Fish and Wildlife Service seeking Endangered Species Act protection for the rusty patched bumble bee. This animal was once very common from the Upper Midwest to the East Coast (including Vermont) and was an important pollinator of crops and wildflowers. Recently it has undergone a precipitous decline.

Historically known from more than twenty-five states, a recent study estimates that the rusty patched bumble bee (Bombus affinis) has disappeared from 87 percent of its historic range. Where it is still found, this bee is much less abundant than it was in the past.

“The charismatic and once common rusty patched bumble bee has suffered severe and widespread declines throughout its range in the eastern U.S. since 1997,” said Dr. Robbin Thorp, professor emeritus of the University of California – Davis. Dr. Thorp is a nationally recognized expert on bumble bees and coauthor of the petition. “The few scattered recent sightings thanks to intensive searches are encouraging, but the species is in critical need of federal protection.”

The cause of the rusty patched bumble bee’s decline has not yet been fully determined. However, in related bumble bees that also are declining, researchers at the University of Illinois have recently found higher levels of a fungal pathogen and lower levels of genetic diversity. Notably, the rusty patched bumble bee was too scarce in the landscape to be included in these analyses.

The leading hypothesis suggests that this fungal pathogen was introduced from Europe by the commercial bumble bee industry in the early 1990s, and then spread to wild pollinators. Although it has not been proven, the hypothesis is supported by the timing, speed and severity of the decline—a crash in laboratory populations of bumble bees occurred shortly before researchers noticed a number of species of formerly common bumble bees disappearing from the wild.

“The remaining populations of the rusty patched bumble bee are small and isolated, and continue to be threatened by diseases from a largely unregulated commercial bumble bee industry, as well as by disease from other sources, habitat degradation, pesticide use and climate change,” said Sarina Jepsen, endangered species program director at the Xerces Society.

With Endangered Species Act protection, remaining populations of this species could be protected from site specific threats and the bee’s habitat could be enhanced. Government agencies would also need to address issues such as the registration of new pesticides that may be harmful to this species and the movement of commercial bumble bees which may transfer disease to wild bumble bees.
Pollinators are critical components of our environment and essential to our food security—providing the indispensable service of pollination to more than 85 percent of flowering plants and contributing to one in three bites of the food that we eat. Bumble bees are among the most widely recognized and well understood group of native pollinators in North America and contribute to the pollination of food crops such as squash, melon, blueberry, cranberry, clover, greenhouse tomato and greenhouse pepper, as well as numerous wildflowers.

“Large areas of insect-pollinated crops, when combined with appropriate pesticide use practices, can contribute to a sustainable landscape for bumble bees,” said Jennifer Hopwood, Midwest pollinator conservation specialist with the Xerces Society. “If the rusty patched bumble bee is listed as an endangered species, private landowners who take actions to enhance habitat for this bee on their land may be eligible to enter into Safe Harbor agreements with the Fish and Wildlife Service or get funding through USDA conservation programs for habitat improvements.”

A Safe Harbor agreement provides assurances that private landowners will not have restrictions placed on their property if they create or improve habitat for an endangered species, and can serve as an incentive to encourage individuals to become involved in restoring habitat to benefit endangered species.