2011-05-20 / Columns
Native bees to the rescue
The chain was easy to follow. No bees, no pollination. No pollination, no food. And though we hear almost nothing of the topic today in the media, bee populations continue to decline.
Since the Western honeybee (Apis mellifera) arrived in North America from Europe in 1622, it has been one of the most reliedupon pollinators for farmers and gardeners alike. But its population has decreased 50 percent since 1950. A massive die-off of the Western honeybees in the U.S. in 2007, called colony collapse disorder, reported a honeybee population decline between 30 and 70 percent. Since then an additional 30 percent decline has been recorded each year.
Reasons given for this loss include pesticides, parasitic mites, disease, migratory beekeeping practices, monocropping and genetically modified crops containing pest control characteristics. In addition, commercially modified plants lacking sufficient nectar and pollen create an even more unfriendly environment for bees to thrive. Honeybee pollination is no longer a sustainable practice.
Alarmed by this decline, horticulturalists began turning their attention to native bees for pollination. As the survival of 70 percent of all flowering plants depends on animal pollinators and 30 percent of human food begins with insect pollination, California’s native bees are essential. Sometimes they are more effective than honeybees.
The efficiency of native bees is due to several characteristics. Some bees, such as squash bees (genus Peponapis), specialize in a single type of plant and therefore concentrate all of their energy on pollinating that plant. Native bees are also adapted to their specific habitat, making them more hardy and tolerant to climatic fluctuations than honeybees.
And third, because native bees gather both nectar and pollen, they must visit the stamen of plants. Nectar foraging honeybees often never contact the stamen and therefore do not induce fertilization.
In addition to providing agricultural benefits, native pollinators are often keystone species in their habitat, providing essential forage for many animals, from hummingbirds to black bears.
But like the honeybee, native bees are also at risk.
Habitat loss, land fragmentation, pesticides and disease take their toll. Commercially modified plants lack the nutrients native pollinators need for survival. While many commercial plants are bred for long bloom time, bright colors and easy growing, they lack the natural components that are essential to native bees.
In order to counteract the factors working against native pollinators, backyard gardeners and farmers are welcoming native bees by planting native plants. Research shows that native plants are four times more attractive than commercial plants to native bees. In addition, the more native bees in backyard gardens, the more native pollinators in agricultural areas.
California hosts at least 1,000 native bee species. Twenty-six are large bumblebees and the rest are small, often overlooked, solitary bees, all searching for homes filled with nectar- and pollen-generating plants ; clean, accessible water; and safe nesting sites.
But before you put spade to soil to grow your native bee garden, ask yourself these questions:
How much sunshine and shade does your yard receive?
What is the wind exposure?
What kind of soil do you have? Does it drain easily or does it hold water?
Also follow these tips:
Choose plants that bloom in several colors. Bees have excellent color vision, and different colors will invite a diverse group of pollinators. Native bees seem to prefer blues, purples, violets, white, and yellows.
Plant the same species in clumps rather than scattered throughout the yard. Large clusters of blossoms serve as an attractor and bring more bees in at one time.
Plant species with different flower shapes. For example the disc flowers of the aster will attract different bees than the tubular flowers of the honeysuckle. Differently shaped flowers encourage bee diversity.
Plant species that bloom at different times of year. Many places in California have the advantage of year-round blossoms, so it’s ideal to find at least one species that blooms each month.
Do not use pesticides. Many pesticides are not specific to the “pest” they eradicate, and many native species die under the guise of killing pests.
Many native bees nest in the ground. As native bees forage close to their nests, it is beneficial to have a few bare patches in your yard for bees to excavate holes to lay their eggs.
A native plant garden that welcomes native bees becomes a highway of life. Imagine if neighbors and farmers had patches of native plants growing near one another. Bees could easily travel from cluster to cluster, transferring pollen and increasing genetic diversity. Native forage grows robust, insects come to pollinate, songbirds come to feed, and life flows up the food chain.
With the single intention of encouraging native bees, a garden with native plants creates an enormous impact on all life—from insect to hummingbird to black bear to humans to squash and tomatoes.
Meghan Walla-Murphy can be reached at the following e-mail: firstname.lastname@example.org.