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Plight of the bumble bee: MN's threatened and endangered bumble bees

Elaine Evans, Extension Educator, Entomology/Pollinators/Bee Lab

Bumble bees are a common site in most Minnesota gardens, but some species have become increasingly uncommon, particularly over the last 20 years. Historically, Minnesota is home to 23 of North America’s 48 bumble bee species. Five species out of these 23 are in serious decline with severe loss of range as well as declines in numbers of bees. Another 3 species are in decline, though the losses are not as dramatic. This means that over one in three bumble bee species in Minnesota are vulnerable to decline. Although bumble bees may still be a common site in gardens, prairies, meadows, and fields, the bumble bee community you are seeing today is most likely a less diverse
group of bumble bees.
The rusty-patched bumble bee is now on
the endangered species list.  Photo:
Heather Holm

On December 11th, 2016, one of Minnesota’s declining bumble bee species, Bombus affinis, the rusty-patched bumble bee, was listed as an endangered species by the U.S. Fish and Wildlife Service. This is the first bumble bee to be given this status and the first bee in the continental U.S. In the United States, endangered species are protected by the Endangered Species Act of 1973, which as amended, is one of the most far-reaching wildlife conservation laws ever enacted by any nation. The listing focuses conservation planning and funding, raises awareness, and by regulation protects listed species from intentional and unintentional harm.

Historically, the rusty-patched bumble bee was commonly seen throughout its range which spread from Minnesota to the east coast, north into southern parts of Canada and south through the Appalachian mountains. Declines were first noticed in the late 1990s. Through the efforts of both professional and citizen scientists, evidence shows that rusty-patched bumble bee populations have declined by about 87%. In addition, their geographic distribution has decreased. They are only found in about 13% of their former range. While evidence of the decline is clear, the cause or causes of the decline are not fully understood. The probable causes include disease (possibly transmitted by managed bumble bees), habitat loss, climate change, and pesticides.

The greater Twin Cities area is one of a handful of areas where the rusty-patched bumble bee is found with regularity. As Minnesotans, we have an opportunity before us to prevent the extinction of a species! Bee-friendly gardening could be a key step in preserving this species. Plant flowers, including flowering trees and shrubs preferred by bees. Aim to have something blooming at all times between mid-April and September. Native plants are a great choice for supporting bumble bees, as well as other native wildlife. Avoid pesticides. If you can’t avoid pesticide use, apply them only where needed and avoid drift into non-target areas. Join efforts to document the rusty-patched and other declining bumble bees. Get out your camera this summer and join Bumble Bee Watch. Strap on your boots and volunteer for bumble bee surveys in the Twin Cities with the Minnesota Bumble Bee Survey or state-wide with the Minnesota Bee Atlas. Together, we can help the recovery of the rusty-patched bumble bee.
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