The 30 percent drop was significant, but was at least less steep than the previous winter.
Honeybee colonies nationwide have reduced in number by 30 percent, based on a recent survey.
The decline is higher than normal but is less than losses of 34 percent sustained for the previous winter.
Experts encourage individuals to plant pollinator gardens and otherwise join in the fight to save honeybees.
Honeybee colonies in the United States reduced in number by 30 percent over the 2010-2011 winter, according to a recently released annual survey conducted by the U.S. Department of Agriculture and the Apiary Inspectors of America (AIA).
The loss was actually lower than for the previous winter, 2009-10, which saw a 34 percent drop in honeybee populations. A 29 percent drop in 2008-9, a 36 percent loss in 2007-8, and a 32 percent decline in 2006-7 preceded the new data.
Jeff Pettis, an entomologist with the USDA who helped to lead the project, told Discovery News that the loss rates are "putting beekeepers out of business." But, he added, "At least it is not getting worse, so in that sense it is decent but not good news."
For the survey, Pettis, along with AIA past presidents Dennis vanEngelsdorp and Jerry Hayes, contacted beekeepers across the U.S. Over 15 percent of the nation's commercial beekeepers, which collectively manage 2.68 million colonies, responded.
"Average loss," per the survey, represents the percentage of bee colony deaths in each business added together and divided by the number of beekeeping operations that responded to the survey. This number is affected more by small beekeeping operations, which may only have 10 or fewer colonies, so a loss of just five colonies in a 10-colony setup would represent a 50 percent loss.
"Total losses," on the other hand, were calculated as all colonies reported lost in the survey divided by the total number of bee colonies mentioned. This number is affected more by larger operations, which might have 10,000 or more colonies. In this case, a loss of five colonies in such a 10,000-colony operation would equal only a 0.05 percent loss.
Of particular interest to the entomologists was the data on colonies that were likely lost due to Colony Collapse Disorder (CCD), a phenomenon where worker bees from a colony abruptly disappear. The beekeepers therefore experience a significant loss, but see no dead bee bodies. For this latest winter, such probable CCD losses came to 31 percent.
CCD is still poorly understood, but Pettis said, "A variety of factors can cause bee losses. We averaged 10 percent winter losses before parasitic mites, around 20 percent winter loss when two parasitic mites (Varroa and tracheal mites) arrived in the 1980's, and now with CCD we are over 30 percent losses in the fall and winter."
"This does not include losses of bee colonies in the summer and spring," he added. "Some beekeepers have 50 percent of their colonies that need to be replaced each year."
North Carolina-based beekeeping activist N'ann Harp, who is the founder of Friends of Honeybees, told Discovery News that "mites and viruses and CCD remain rampant everywhere in the U.S."
The problems seemed to come on suddenly and with a vengeance in recent years.
"When our local beekeepers began hearing about CCD in 2003-2005, we hadn't seen any of it here, and figured, 'Oh, that's a commercial-pollination problem. It'll never happen here. Then it arrived here, where there are few to no commercial pollinator beekeeping businesses."
Harp suggested that unhealthy breeding practices, weakened immune system strength in honeybees, mites, pollution, pesticides, viruses and more have created a "perfect storm" of combined impacts.
She said some beekeepers are staving off losses by employing a "tough love approach of stopping all chemical treatments and allowing the surviving colonies and successive generations of honeybees to slowly develop resistance and strength."
Pettis suggested that concerned individuals could also help to turn the population tide for honeybees.
"Plant a pollinator garden," he advised. "Become a beekeeper or let a beekeeper place bees on your property and in larger areas support programs that look to increase plant diversity that allows bees and other pollinators to have food throughout the year. Habitat loss is a major issue, and pollinator friendly plantings can help in urban and rural areas."
He reminds that all pollinating insects and animals face threats now, so habitat improvements can help many such species, and not just honeybees.