Wild bee die-offs at center of new research

08/07/2019

The plight of honey bees has received nationwide attention for the past decade, as conventional agricultural practices, a changing climate and habitat loss have decimated their numbers. Yet the spotlight has largely passed over thousands of native bee species, whose populations have also declined. 

For Nina Sokolov, a Ph.D. candidate from the University of California, Berkeley, the survival of native bees, which contribute an estimated $3 million a year in pollination services for crop production in the United States, is equally important. Ms. Sokolov brought her preliminary research to Point Reyes Station last month for the Marin Conservation League’s quarterly agricultural land use committee meeting.

Ms. Sokolov’s research is among just a handful of studies exploring how common viruses might be transferred—including by parasites such as the varroa destructor—between honey bee and native bee populations. The issue is of particular concern in California, which is home to 1,600 of the 4,000 bee species nationwide and imports up to 70 percent of all the country’s honey bees to the Central Valley for agricultural production.

As part of her research, Ms. Sokolov is looking at honey bee—Apis mellifera, originally from Europe, is the most common species for honey production—and native bees at three test sites, including a cattle ranch in Novato that keeps 400 commercial hives, a commercial operation of the same size in the Sierra Nevada and a wildflower farm with eight backyard hives in Sonoma County. 

Her primary questions include: What are the patterns of virus infections in honey bees and native bees over time? How does the mass importation of honey bees into California impact the type of viruses affecting bees? Is there evidence of a spillover of viruses from honey bees to native bees, and are some native species more tolerant or resistant than others?

Ms. Sokolov’s working hypothesis is that viruses spike in honey bees first, and then spill over into native bee species. “I predict that the highest prevalence will be found in areas with the least forage, and that viruses will not be found at detectable levels in bees isolated from honey bees,” she said in her presentation to the agricultural committee.

Speaking at the Marin County Farm Bureau offices, Ms. Sokolov underscored the importance of her research: last winter, an estimated 37.7 percent of the managed honey bee colonies in the United States were lost, representing the highest level of losses reported since 2006, according to the Bee Informed Partnership, which is sponsored by the Department of Agriculture. To make matters worse, the department will no longer be collecting data on colony losses, following recent funding cuts.

Ms. Sokolov said there is much less research on wild bees, though their declines have been similarly drastic. The International Union for Conservation of Nature reports that a quarter of the 47 species of U.S. and Canadian bumble bees risk extinction.

As she completes her research, Ms. Sokolov told the agricultural committee that there are several ways for residents to help. She invited any managers of commercial hives to participate in her research, while everyone is welcome to participate in data collection through the online site inaturalist.org. Planting flowers for native California bees is another way to nurture those populations.

Bonnie Morse, who manages hundreds of commercial honey bee hives in the county through a business she co-owns with her husband, Gary, said she has moved most hives out of West Marin in recent years due to low local honey production.

In Tiburon, Ms. Morse gets about 120 pounds of honey off of one hive in a backyard. In Lucas Valley, where she manages 15 hives on 5,200 acres of ranchland for the landowners, she gets just 100 pounds a year.

“That gives you an idea: West Marin does not have the forage for honey bees,” she said. But, she added, “it’s not just the forage, it’s also about the flowers and the nectar. In West Marin versus the 101 corridor, where there is a lot more irrigation and less grazed land, we don’t see the bees being able to naturally produce a lot of wax and combs during the year.”

Nevertheless, Ms. Morse, who started the county’s annual bee survey in 2009 through her work for the Marin Beekeepers Association, said Marin’s bee populations continue to dwindle. Loss rates in Marin were 53 percent in 2009 and 2010 when she started the survey, but dropped down to 34 percent in 2015. 

The last few years, however, have been “brutal,” with loss rates back up to 70 percent, which she hypothesized might be due to the effects of the state’s large-scale wildfires.

In addition to managing hives for other businesses and individuals, a major goal of the Morses’ business, Bonnie Bee and Co., is to raise honey bees that show resistance and tolerance to pathogens such as the varroa mite. Before Ms. Morse established a local breeding program that allows her to select for various traits that contribute to resilience, beekeepers in Marin were importing bees from commercial operations that are not as selective.

Ms. Morse agreed with Ms. Sokolov that creating habitat, particularly by growing flowers, was probably the most effective measure to take, even more so than raising new colonies of bees.

Although she focuses on honey bees, Ms. Morse said, “Native bees are certainly being annihilated,” and that’s not something she takes lightly.

“In some ways, Nina’s research could actually hurt our business if it shows, for instance, that limiting our colonies will help to protect native pollinators,” she said. “But that information is something we really need to have in order to develop best management practices and to know how to responsibly maintain native bee populations.”