Scientists try to stem the tide of bee losses
Bees pollinate about one-third of the world’s food supply, according to Sustain, a nonprofit agriculture policy organization. Bees pollinate all manner of fruits, vegetables, crops, and even some of the wild grasses used to feed cattle and other livestock.
Their impact to the U.S. economy are valued at about $15 billion per year, according to Scientific American. During the winter of 2018-19 bee keepers across the country lost an estimated 38% of their honeybee colonies mostly due to an Asian parasitic mite that is resistant to some pesticides that kill mites.
The bee population in Arkansas is in decline and it could have a devastating impact on the state’s agriculture industry. Neelendra Joshi, assistant professor of entomology for the University of Arkansas System Division of Agriculture, uses the research tools of his discipline to understand the greatest threats to the state’s hundreds of bee species and learn how to protect them.
“There are an estimated 25,000 species of bees that provide pollination services to the world,” Joshi said. “Our research has identified more than 100 species in Arkansas, and we estimate that there may be as many as 300 to 400 native bee species in the state.”
Using various sampling techniques, Joshi has determined that different species of bees are distributed to different areas of the state, mainly based on local resources like habitat and food sources.
Bee populations, both managed and wild, are in decline everywhere, Joshi said. Extensive research is underway nationwide to fully understand the causes, but the known threats are many.
Interactions among many stressors have created colossal maladies hitting bees at one time, Joshi said, and in many cases, the combinations have caused additive impacts. Also, he said, the factors causing distress in wild bee populations tend to be different from those harming domesticated honeybees.
Managed bee populations often suffer from restricted diets when they are moved from location to location to pollinate specific monoculture crops, where they forage on only one kind of flowering plant. Joshi said these bees are not getting the balanced nutrition necessary to maintain good health.
Also, the breeding and handling practices for managed beehives tend to make the bees vulnerable to rapid spread of disease pathogens or parasites and other pests.
“The biggest threats to wild bee populations are loss of nesting habitat and loss of native flora that are primary food sources,” Joshi said.
Most people think of bees living in hives, either in managed, human made hives or wild hives in trees or, on occasion, attics. But wild bees live in many different kinds of nesting sites, most of which are vulnerable to loss because of human development.
“Seventy percent of bees are ground-nesting,” Joshi said. “Many others live in tunnels and cavities.”
Bees can be quite industrious, rivaling human developers in creating living space. Joshi said they may occupy or even build cavities in the ground, tunnels in trees — either moving into abandoned beetle galleries or, as in the case of carpenter bees, creating their own — or live on the ground. Mason bees use mud, sand, leaf particles and other materials to build nests.
Bees lose habitat to human development like urban expansion, road building, logging, land clearing and tilling for agriculture, forest fires, and other natural or human-made reduction in wild land and forests.
Urban spread and monoculture agriculture contribute to loss of wildflower food sources for wild bees, Joshi said.
“Bees require nectar and pollen from diverse floral resources to meet their nutritional needs,” he said. “Popular garden plants and the ‘sameness’ of monoculture farming systems do not provide dietary balance.”
Many other things also contribute to population decline, Joshi said, including pesticide use.
Joshi and his lab have conducted studies to measure the effects of common pesticides and biological alternatives on bee species. The studies included determining what levels of exposure are fatal, and those from which bees of different species can recover.
While it’s easy to point the finger at agriculture for pesticide use, Joshi said homeowners and gardeners use precisely the same pesticide chemicals, and often with less restraint.
Global climate change also is likely contributing to bee decline, though scientists are still collecting data. While Joshi said he had not seen evidence of it in Arkansas, there is much concern that rising temperatures may cause flowering cycles and the beginning of seasonal bee activity to get out of sync.
“Solitary wild bees could emerge early and not find any food,” he said.
Managed bees and wild bee populations have to compete for ever-shrinking resources, compounding the problem.
Beekeepers who maintain managed populations for breeding, honey or pollination services are already looking to researchers for the answers they need to restore health and stability for their hives.
Joshi said everyone can make changes to help wild bee populations recover. Homeowners and gardeners should be careful about pesticide use, he said. Farmers use the least amount necessary to protect their crops for economic reasons. Homeowners use pesticides for comfort — to keep insects out of their homes — and gardeners use them for aesthetic purposes, to keep their gardens pretty. Joshi recommends using pesticides that are less toxic to bees or natural alternatives, if possible, and to time their use for when bees are not active or present.
Maintaining non-compacted, well-drained soils offers suitable nesting substrates for ground-nesting bees, Joshi said. He suggested drilling holes in scrap pieces of wood and hanging them in trees at least 5 to 6 feet off the ground for tunnel-dwellers.
To provide food sources, Joshi recommended planting a variety of native wildflowers.
“Many exotic garden plants will not be suitable,” Joshi said. “It’s best to use a mix of colors and plant heights, as well as a sequence of plants that bloom at different times of the year while bees are active,” usually from April through about mid-October, he said.
Joshi is conducting a study now to correlate specific pairings of bee species to plant species in Arkansas. “We’re looking at different flowers to identify which bee species are using them,” he said.
“Different species have different preferences,” Joshi said. “We want to learn what those are.”