NEBRASKAland Magazine is dedicated to outstanding photography and informative writing with an engaging mix of articles and photos highlighting Nebraska’s outdoor activities, parklands, wildlife, history and people.
Issue link: http://mag.outdoornebraska.gov/i/853309
28 NEBRASKAland • AUGUST-SEPTEMBER 2017 know how abundant they are. The only time they can be observed is during mating and when queens are searching for a colony to usurp. According to the Xerces Society and the IUCN North American Bumblebee Specialist Group, nearly a quarter of the 46 bumblebee species in North America are at risk of extinction. In Nebraska, seven of our 20 species are considered vulnerable and declining in population. A study conducted between 1999 and 2002 by the University of Nebraska and a variety of collaborators (the Bumble Boosters program) found 19 out of the 20 bumblebee species, with the only exception being the Morrison bumblebee (Bombus morrisoni), which was found historically only in the extreme western parts of the state. The study found several bumblebee species in parts of Nebraska from which they had not been previously reported. However, not all of the news was positive. Today, the American bumblebee (Bombus pensylvanicus) is found in much lower numbers than it used to be, especially in the eastern part of the state. The yellow bumblebee is less abundant today as well, though it has never been one of the more numerous bumblebees in Nebraska. Other bumblebee species are declining across much of their historic range in North America, but their status in Nebraska is not well known because few people are out looking for bumblebees, especially in western parts of the state. Habitat Loss, Pesticides and Disease Habitat loss is a major factor in the decline of bumblebee populations, as it is for other bee species and many other organisms. Though bumblebees are not habitat specialists the way some other organisms are, in order to support large colonies, they do need abundant wildflowers, including a wide diversity of flowering species through the growing season, often from several different habitat types. Conversion of land to row crop agriculture has left pollinator habitat restricted to field edges and corners in many parts of the country, making foraging more difficult. In recent years, many of those edges and corners have also been converted to row crops. This has not only made food more scarce, but has also removed nesting habitat from large swaths of the landscape. In areas where habitat is less fragmented, bumblebees and other pollinators can still struggle to find sufficient resources. Many grasslands and woodlands have lost a number of their wildflower species because of chronic overgrazing and/or broadcast herbicide application. Much of the remaining habitat is either hayed or grazed, which can reduce or eliminate the availability of flowers during some or all of the growing season. In addition to habitat loss and fragmentation, bumblebees also suffer from the same kinds of pesticide use as other bees and insects. Neonictinoid pesticides, in particular, have been shown to have adverse impacts on bees and other beneficial insects. Pesticide and herbicide application can affect bees indirectly by killing pollen and nectar producing plants, and by causing bees themselves to become sick or die. Diseases are also listed as a major factor in the decline of bumblebee populations. The fungal pathogen Nosema bombi, for example, affects both bumblebees and honeybees. Commercial greenhouse operations that use bumblebees can be hot spots for the fungus, and scientists are investigating what impact those operations might have on spreading the disease to wild bumblebees. Pollinator Conservation Bumblebee population declines are almost surely a result of multiple forces. Habitat loss and fragmentation likely makes populations more vulnerable to other stressors like pesticides and disease. Successful conservation of bumblebees and other pollinators will mean addressing all of those factors, but habitat is probably the most important. While it's not feasible or desirable to return the bulk of Nebraska's cropland to prairie, there are ways to make agricultural landscapes much more friendly to bees. Conserving habitat between fields and in less productive areas of cropland is very beneficial. Bumblebees primarily nest in small mammal burrows, and sometimes in rotten trees or old hay bales. Removing old shelterbelts and plowing up field edges removes many potential nesting sites for bumblebees. One of the most important aspects This brown-belted bumblebee is feeding on the appropriately-named Rocky Mountain Bee Plant in the Nebraska Sandhills.