by Sally Colby
Elias Bloom, PhD candidate in entomology at Washington State University, is in the middle of a five-year study of wild bees on diversified farms in western Washington State. The project began in 2014 with a study of urbanization and how it impacts bee diversity and bee pollination services. Bloom says while the global value of pollination services of bees is relatively unknown for organic farming systems, the value of the work of pollinators is billions of dollars annually for farming systems worldwide.
“Not only are honeybees responsible for pollination, but wild insects, including wild bees, contribute significantly to pollination of many crops,” said Bloom, adding that humans rely on pollinated crops for proper nutrition.
In general, organic farmers rely on bee communities rather than populations of a single species to achieve effective pollination services. “In conventional farming, we typically see low diversity of these species in farming systems,” said Bloom. “As we move to organic farming, we see very high diversity of bee species. With increased biodiversity (the number of species) and the equal abundance of species, there is an increase in ecosystem services, i.e., pollination.”
Bloom says there has been significant research on honeybees, but there’s no good, specific data on honeybees or wild bees on organic farms. “We do know that providing extra floral resources and reducing the use of pesticides in general improves bee community health,” he said. “We’ve been measuring bee biodiversity on farms in urban areas, on certified organic farms and on farms that are transitioning to organic. Now we have a baseline and can manipulate habitat and forage for bees and see how it influences biodiversity and pollination services.”
Organic acreage and small-holder farms are abundant and growing in Washington State. However, many are surrounded by rapidly expanding urban areas. In King County alone, urbanization has increased by more than 200 percent since 2007. However, although the landscape has become more developed and fragmented by urbanization, there is good evidence that urban areas can serve as a source of biodiverse bee communities.
Providing habitat for bees on small organic farms will become more challenging as landscapes change. “Wild bees are becoming increasingly rare or even extinct due to the landscape level change not only due to urbanization but also due to the increase in large scale farming systems. One way we can provide habitat for bees is the use of roadsides. In Washington State, there are approximately 150.48 miles of roads that border organic farms that require pollinators. These roadsides haven’t been restored, but restoration, if suitable, would serve as a source of bee habitat and increased ecosystems on the farm.” Bloom encourages organic farmers to look at this option as a means of encouraging pollinator populations.
Another option for habitat development is power line easements, which could connect organic farms with strong bee communities. Bloom says such projects would require interested citizens working on policy at local state, and national levels.
While a farmer may want to encourage a bee group to settle on his farm, Bloom says it can be difficult to restore bee populations to the farm property itself. However, bees may live on natural land adjacent to farms. “The conservation of natural areas is going to be important because these natural lands can provide bees that will spill over into farming systems and provide pollination services,” said Bloom. “This is likely going to be species-dependent.”
Bloom’s research showed organic farmers who create and maintain nest substrate for certain bee species will see more cavity-nesting bees. Planting a dedicated floral buffer strip is one effort that proves to be worthwhile. “Research shows that putting in a floral buffer strip will increase the number of native bees visiting,” said Bloom. “A farm that put a habitat strip on the margin of the farm started to see significantly more native bees visiting the blueberry plants.”
Another research finding was that broad scale diversification of crops brings more bee groups. Bloom cited California research that showed providing native plants increases the number of bees more dramatically than using exotic plants. “Consider introducing floral diversity either on the margin of your farm or intentionally in the field by growing a lot of different crops,” he said. “Select plants that are native and helpful to getting more bees onto the farm.”
An important finding was that certified organic farms tend to host more native bees compared to farms that use organic practices. Switching from a conventional farming system to organic practices can increase bee biodiversity by up to 75 percent.
Bridget McNassar, manager of the native plant nursery and conservation manager at Oxbow Farm and Conservation Center in Carnation, WA, defines and explains the use of native plants.
“Native plants are desirable because they are adapted to the local soils and climates, and thrive once planted and established, they require minimal care,” said McNassar. “Native plants are more effective for wild bees because they’ve co-evolved with them. Both the bees and the plants have lived in the area together for thousands of years.” McNassar added when plants are bred to be more showy or colorful, some of the traits that made them attractive to bees are lost.
When selecting native plants to attract and feed bees, determine which plants are suitable for your region. McNassar recommends the Pollinator Conservation Resource Center, available from the Xerces Society. “They’ve broken down the U.S. and Canada into 10 eco-regions,” said McNassar. “You can click on your eco-region for a list of pollinator plants.” Another resource is the Pollinator Partnership, which has planting guides for 32 regions. Native plant societies, conservation districts and cooperative extension can also provide information.
Choose a wide variety of species that bloom over the widest range of seasons possible; from early spring to late fall. This will provide nectar and pollen so bees will stick around all season. Ask and make sure a plant is native, not wildflower — they aren’t the same. “Early bloom plants can be especially important,” said McNassar. “There are several species of bees that have multiple generations throughout the season, so once they emerge in spring, if they have plenty of food, they’ll be more successful.”
Select flowers with a variety of appearance — shape, size color — to attract different bee families. Plants such as native bunch grasses don’t produce flowers that are useful to bees, but provide overwintering habitat and nesting sites for bumblebees. Purchase seeds or plants from sources that are as local as possible. McNassar says the Xerces Society has a list of nurseries and seed sources, along with a list of 17 conservation seed mixes for various regions.
Source seeds and plants as early as possible in the season. Farms in most areas will plant or seed in fall, and many native species require a cold period. This spring, when seeds are selected and sown, is the time to talk about what to order for fall to ensure the supplier will have what you want.
Most native plants and seeds are not certified organic, so the grower will have to fill out a commercial availability record.
For more information on suitable native plants for bees, visit the Xerces Society at www.xerces.org/
Encouraging wild bees on organic farms
by Sally Colby