February 28, 2013 _ The tricoloured bumble bee used to flit around blueberry fields in the Maritimes pollinating flowers and helping deliver bumper berry crops.
“In the 1990s it started to really decline,” says Steven Javorek, a landscape ecologist with Agriculture Canada. He says the once-common bee with its distinct orange belt is now rarely seen, joining the growing list of wild pollinators in trouble.
While they may be lowly insects, Javorek and his colleagues have amassed evidence that their demise is not just an environmental concern but a threat to global food production.
In an international study released Thursday they say wild pollinators are critical, if often overlooked and abused, players in agriculture.
They pollinate crops more effectively than honeybees leading to twice as many flowers developing into fruit and seed, the researchers report in their study in the journal Science.
Without steps to conserve wild pollinators and protect their habitats “the ongoing loss of wild insects is destined to compromise agricultural yields worldwide,” the scientists warn.
“When you look at the role of wild bees in the global sense, it’s quite profound,” says Javorek, at the federal Atlantic Food and Horticulture Research Centre, in Kentville, N.S. “The loss of their services cannot be replaced by just bringing in more honeybees. That is what is so striking about this research.”
It’s estimated three quarters of global food crops depend at least in part on pollination by bees, butterflies, flies, and sometimes bats and birds.
The study of 41 crops – everything from South American coffee to Canadian blueberries – was undertaken to try and find out if “managed pollinators,” such as commercial honeybees, could compensate for the decline in wild pollinators seen in many parts of the world, including Canada.
The scientists combed through data from 600 fields around the world growing 41 different crops. They report that wild pollinators “enhanced fruit set by twice as much as” honeybees.
The study concludes that honeybees add to the pollinating power of the wild insects, but can’t replace their “pollination services.”
Javorek likens it to the stock market. Investing in a single stock is unwise, he says, and so is relying on one type of pollinator.
He says the importance of the wild bees is evident on low-bush blueberry farms in the Maritimes, which were included in the study. The berries, which are native to the Eastern Canada, are a now lucrative crop grown commercially from Quebec to Maine.
Wild insects share an evolutionary history with the blueberries and Javorek says they will pollinate the plants’ flowers regardless of the weather.
“They fly on those kind of wet, cool spring days when the crop is blooming, whereas honey bees are still tucked in their hives,” he says.
In years with marginal weather, “you really see a big bump in production on the fields that still have a healthy wild bee communities,” says Javorek. “That’s where you really see it.”
Study co-author Lawrence Harder, a flower and bee specialist at the University of Calgary, says honeybees often visit many flowers on the same plant, resulting in inbreeding. Wild pollinators tend to visit fewer flowers per plant, instead moving from plant to plant spreading pollen as they go. This results in more genetic “out-crossing” and higher quality fruits and seeds.
Harder says much could and should be done to protect the 800 wild bee species in Canada, and 20,000 species worldwide.
Many wild bees live in nests in the ground that are “eradicated by machinery chewing up the soil,” Harder says. And planting huge fields of the same crop means there is often little pollen and nectar for bees to eat.
“These wild bees, they need food during their entire active lives,” says Harder, noting how crops like canola produce bright yellow flowers for a few weeks.
“When the field is bright and yellow it’s just a cornucopia,” says Harder. But when the flowers die the fields are a “wasteland for bees” which must find food elsewhere.
He says planting native plants along ditches and roadways would help. So would reducing use of pesticides that can harm and kill wild bees along with the pests that farmers are trying to eliminate.
A second study, also in Science on Thursday, points to huge declines in wild pollinators. A U.S. team revisited sites in Illinois that had been studied in the late 1800s. They found half of the bee species present historically are now gone.
The study is “particularly intriguing because of its historical aspect,” Harder says. But he notes that pollinator declines are not restricted to Illinois.
Several once common bees are in decline in Canada including the tricoloured bumble bee in the Maritimes and the western bumble bee in B.C. and Alberta. And the rusty-patched bumble bee, last see in Southern Ontario in 2009, has the dubious distinction of being the first bee to be officially declared an endangered species in North America.
Pesticides, habitat loss, climate change and disease spread by commercial honeybee operations are believed to be contributing to the wild bee losses.
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