“A bee just flew down my top!” shrieked a volunteer at a north Atlanta community garden as she leapt to her feet from a bed of crook-necked squash she’d been harvesting.
“Don’t kill it!” shouted the garden’s volunteer director as she rushed to the rescue of the bee. The insect, she quickly concluded, was in far more danger than the frightened worker, who had begun a frantic arms-flailing, high-stepping and highly vocal dance in hopes of freeing the bee before it stung her.
Saving honeybees, native bees and other pollinators is important because of their economic value to crop production and because their populations are at risk in many places across the United States. Insects pollinate $18 billion to $27 billion worth of U.S. crops annually, according to Nancy Adamson, a pollinator conservation specialist with the Xerces Society and the USDA-NRCS East National Technology Support Center in Greensboro, N.C. Put another way, one in three mouthfuls of food and drink Americans consume is the result of insect pollination, according to Adamson’s program.
Bees critical to pollination
“Bees, in general, are the most important crop pollinators,” said Adamson. “That’s because of all of our insects bees are the only ones that collect nectar and pollen and depend on it all of their lives.
“Bees also play a critical role in pollination because they exhibit flower constancy,” Adamson added. “That means,” she explained, “that once they find a good source of nectar or pollen, they will keep visiting that kind of flower until the nectar or pollen is depleted. This is good for pollination. They save energy by visiting flowers they know have good resources.” (Watch a short a video of wild bees pollinating crops.)
But bees are in trouble.
The number of honeybee colonies reached a high of about 6 million in 1945 but dropped to about 2 million in 2005, according to the U.S. Department of Agriculture. Since 2006, the decline has not only continued but has accelerated, according to the Xerces Society, a nonprofit group based in Portland, Ore., that protects wildlife through the conservation of invertebrates and their habitat. Reasons for the decline include honeybee colony collapse disorder and a variety of human activities, including habitat loss through urban development, the amount of land devoted to agriculture, the introduction of non-native plant species and insects for biological control, diseases and pesticide use. Though we know less about the status of other bees, we know that several bumble bee species have declined dramatically as well, likely due to the introduction of diseases.
Bee declines are detrimental to farmers because they are occurring at the same time that the amount of land devoted to agriculture is increasing. From 1961 to 2006, the percent of global cropland requiring bee pollination rose 300 percent, according to Adamson’s program and research by Marcelo Aizen and Lawrence Harden. “We still don’t have enough honeybees for almond pollination in the United States,” Adamson pointed out, adding that “new research is looking at ways to support wild bees and blue orchard bees (a native managed bee) that pollinate almond.”
Honeybees, which interestingly were imported from Europe by colonists in the early 1600s and are not native to North America, are not the only bees at risk. The 4,000 species of bees native to North America — 700 species in 66 genera in the eastern United States alone — are facing the same threats from human activity as honeybees.
Wild bees are also efficient pollinators. A recent international study of 41 crops found that wild pollinators enhanced setting of fruit twice as effectively as honeybees. In the U.S., more than 100 species of wild bees visit apples in Georgia, New York and Pennsylvania, blueberries in Michigan and cranberries in Wisconsin. More than 80 species of native bees visit berry crops in New England and more than 60 species visit tomatoes, sunflowers and watermelons in California. The workhorse of the native bees, said Adamson, is the familiar bumble bee. Some other crops that rely on native bees for pollination include squash, alfalfa, peaches, cucumbers, cantaloupes, pumpkins, canola, strawberries and coffee.
Bees not the only native pollinators
Bees are not the only native insect pollinators. Other insect pollinators include butterflies, moths, flies, beetles and wasps. Insect pollinators are considered ecological keystones because they not only ensure pollination of plants that we depend on for food, shelter, and oxygen, but they are at the base of food chains.
More than 85 percent of flowering plants rely on insects as well as animals such as birds and bats to transfer pollen so the flowers can set fruit. Pollinator-produced fruits and seeds feed more than human populations. They comprise 25 percent of the global bird and mammal diets around the globe. Insects themselves are vital food for other wildlife.
A home test for pollination
Consumers can see the effect of pollination right in their own kitchens. Cut an apple in half through its middle and look at the seeds. They should be in five compartments in the shape of a five-pointed star.
If the apple has two seeds in each compartment, it was completely pollinated by bees. If there are less than 10 seeds, not enough pollen reached the flower’s stigmas to develop all of the seeds.
A poorly pollinated flower may be aborted or develop into misshapen fruit.
Homeowners can help
Fortunately, there is plenty that home gardeners can do to help save pollinators. Some of the ways backyard gardeners can help is to:
- Create diverse habitats.
- Select plants for the landscape that will bloom throughout the growing season (spring, summer and fall). Flowering trees are an important source of pollen in most of the country because many of them flower in the spring before the perennials have had a chance to bloom, said Adamson. She also encourages gardeners to plant flowers that will bloom in summer when there are often gaps in blooms because of the stress of summer heat. Asters and golden rod are good sources of pollen in the fall, she added.
- Include at least three species that will bloom in each season
- Plant locally native plants (if you use introduced species, avoid invasive plants).
- Provide shelter for nesting sites such as stacking hollow bamboo tubes for cavity nesters, leaving stumps, creating brush piles, planting species with pithy stems such as elderberry, blackberry or sumac, or even leaving some areas as bare earth for ground-nesting insects.
- Avoid deep tillage to control weeds in your backyard vegetable garden (pollinator-friendly alternatives to tilling include planting cover crops such as buckwheat or crimson clover, or mulching).
- Conserve undisturbed or un-mowed areas because they are possible nesting sites for bumble bees and overwintering sites for bumble bee queens.
- Avoid using pesticides, especially when bees are active.
- Be aware that not all-organic-approved pesticides are safe for bees (ones that are safe when applied to non-blooming crops or at night -- i.e. not directly to bees -- are insecticidal soaps, horticultural oils and Neem).
The Xerces Society has a user-friendly resource guide called Pollinator Conservation Resource Center to help home gardeners across the country find out how they can create and maintain a pollinator friendly habitat.
The main page of the guide features a map of the country divided into regions marked by various colors. To use the guide, simply scroll over the map and click on your region of the country. This will bring up a page with links to lists of plants to attract pollinators, conservation guides, pesticide guides, native bee nest management guides, native pollinator plant nurseries and bee identification and monitoring resources.
For questions or comments about the Resource Center, or to suggest additional content, contact Eric Mader, Xerces assistant pollinator program director, at email@example.com.
And when you are in the garden, don’t be overly concerned about being stung by a bee. Unless you disturb a nest or stray too close to one, bees don’t want to sting you, said Adamson. Most native bees are solitary, so they don’t have a colony to defend, like honeybees. They are focused on collecting nectar and pollen. “If a honeybee stings you, she will lose her stinger and, basically, her whole rear end will come off and she will die,” Adamson said.
Related stories on MNN: