Can a bee learn to fly over, instead of across, a busy highway? Washington State University entomologist Douglas Walsh is working with the Washington State Department of Transportation (WSDOT) to find out.
He will study alkali bees and their flight around a stretch of U.S. Highway 12 in central Washington to help WSDOT minimize the impact of a proposed highway improvement project on the native insect.
WSDOT is sponsoring a four-year, $232,000 study by Walsh and his research team to survey alkali bee population density in nesting beds that potentially would be affected by the project. The team will determine flight paths between beds and nearby alfalfa fields in relation to the project’s proposed route and assess whether effective barriers can be installed along the roadway to alter vertical and horizontal flight.
The segment of WSDOT’s larger U.S. Highway 12 project, referred to as Phase 7A and 7B, proposes rebuilding the roadway as a four-lane, divided highway from the east side of Nine Mile Hill to just west of Woodward Canyon Road.
According to the department website, more than 10 million tons of cargo are transported over this section each year, and slow-moving trucks and recreational vehicles congest the two-lane highway. The bottleneck is dangerous: Since 1991, the corridor has seen roughly 1,080 collisions causing 414 injuries and 30 deaths.
Second-largest alfalfa seed producing area
The proposed new highway would cut through the Touchet-Lowden agricultural district in Walla Walla County. The 84-square-mile area supports 16 growers producing 12,000 acres of proprietary alfalfa seed varieties for six different seed companies, according to one of those growers, Mike Buckley. That acreage makes Walla Walla County the second largest alfalfa seed-producing area in the United States, he said, with retail sales exceeding $50 million in 2009.
The same area also has the world’s largest community of non-honey bee pollinators in the alkali bee, Walsh said. A 1999-2006 study published in Apidologie by U.S. Department of Agriculture entomologist James Cane showed that nearly 17 million alkali bees called the Touchet Valley home.
Slightly smaller than the honey bee, with black and green-yellow bands on its thorax, the alkali bee is considered the most effective alfalfa pollinator. Some local alfalfa growers have relied on the bees for more than 50 years to pollinate their crops.
Unlike honey bees, female alkali bees are solitary nest builders, but many will build nest beds close to one another. Females will forage for miles to find nectar to establish their nests. They also spend six weeks of each year actively foraging - and flying - which puts them at risk in road traffic.
Walsh said alkali bees need established bee beds, between 2-10 acres, where a surface crust of salt or alkali helps preserve moisture in the below-ground nests. The bees are vulnerable to habitat loss since cultivation, grazing and disturbance by off-road vehicles can damage bee beds.
In 2009, WSDOT completed an environmental assessment regarding effects of the proposed project. One finding of the report was that the project may adversely affect alkali bee populations within one mile of the new roadway.
"WSDOT understands the impacts the new roadway may have on this important resource, and we are working with WSU and alfalfa seed farmers to identify and consider design ideas that can minimize the effect of the new alignment on alkali bees,” said Jason Smith, environmental manager for WSDOT’s south central region.
"There’s a reason why they grow alfalfa seed here. Growers are only permitted to draw water from the Touchet River in winter and spring, but not summer because of salmon,” Walsh said. "Fortunately, water stress causes alfalfa to bloom, so this area is the ideal place to grow alfalfa seed.”
WSDOT approached Walsh to determine alkali bee populations, where and how far they travel and how high above the roadbed they can fly. Every fall, Walsh will survey bee beds by taking a core soil sample to see how many pupae are in each.
To learn how high the bees can fly, Walsh and graduate student Amber Vinchesi attached a bee sweeper rack to a car. The rack has 13 nets at varying heights, 1-13 feet above the ground, to capture bees in flight. Thirteen feet matches the height of a typical semitrailer on the highway.
Walsh and his team constructed a 14-foot-high bee mesh barrier along a quarter mile highway stretch in the Touchet-Lowden corridor. They observed foraging alkali bees climbing over the mesh and flying another 75 feet at the same height – clearing the roadway - before dropping back down to ground level.
"It’s been working pretty well,” Walsh said of the barrier. "The Department of Transportation really liked it because it looks like an inexpensive way to protect the bees.”
Preservation a priority
WSDOT and other state governmental agencies are required to consider native bee populations in their projects since the U.S. Congress made native bee preservation a priority in the 2008 Farm Bill, Walsh said. With the U.S. Highway 12 project still in preliminary design, and WSDOT preparing right-of-way plans, the department and Walsh will work to determine a solution that meets everyone’s needs.
"This project will decrease the impacts of WSDOT highway construction on both farmers and their important bee resource,” Walsh said.