How To Protect Our Imperiled PollinatorsA decline in bees and other pollinators is trouble for the entire country. Here's what you can do about it.
One sunny morning last summer, Hachiro Shimanuki strolled into the backyard garden of his home in Maryland. With camel-hair brush in hand, he stood poised above the drooping yellow blossoms of a tomato plant. Flicking the brush across the inside of a flower, he gently spread pollen, or male reproductive cells, to the stigma, or female part of the plant. This process, known as pollination, is essential for vegetable, fruit and nut production, and is often performed by bees.
"I couldn't find enough pollinators in my small yard so I used the camel-hair brush to pollinate my tomatoes and peppers," says Shimanuki. As head researcher at the U.S. Department of Agriculture's Bee Research Laboratory in Beltsville, Maryland, Shimanuki has charted a 25 percent decline in the United States' population of managed honeybees during the past decade. This decline is being felt far beyond Shimanuki's backyard. Growers of some commercial crops--such as almonds, blueberries, apples, pears, broccoli, squash, pumpkins and cucumbers--are increasingly relying on migrant beekeepers to pollinate their plants. The stakes are high: bee-dependent crops are worth $10 billion a year in the United States.
Domesticated honeybees are not the only pollinators in trouble these days. Many species of butterflies, moths, birds, bats and other mammals are also in retreat, threatening not only commercial crops but a wide range of flowering plants. "Action must be taken to reverse these trends," says Stephen Buchmann, an entomologist at the U.S. Department of Agriculture's Carl Hayden Bee Research Center in Tucson, Arizona. According to Buchmann, only a few of these pollinators (mainly Hawaiian bird species) are protected by the federal Endangered Species Act. "This is simply because the world is focused on the charismatic megafauna--the lions and tigers and bears," he says. "The little things that run the world, including bees, butterflies, bats and hummingbirds, go unnoticed and unprotected until it is sometimes too late."
Not all plants require animal pollination--grasses, for example, have light, dry pollen that is carried by the wind. The pollen of about 80 percent of other flowering plants, however, is too heavy to travel on air currents and needs to be moved from anther to stigma by an external agent. This usually happens by accident, when a bee, butterfly or bird visits a flower in search of a meal of nectar or pollen. Pollen grains from the anthers of the male stamens stick to the pollinator's tongue, head, wings or legs. When the pollinator visits another flower of the same species, it unwittingly deposits the fertilizing pollen on the stigma of the female pistil.
If not for bees, which are responsible for pollinating more flowers than any other creatures on Earth, many plants would be unable to set and produce fruits or seeds. "Every third bite of food we eat, our clothing--cotton and flax--plus many beverages and some medicines come directly from the pollinating activities of these animals," says Buchmann, coauthor of the recently published book The Forgotten Pollinators.
Honeybees--imported from Europe in the 1600s and managed by beekeepers--are the most important pollinators, according to Shimanuki. "They pollinate over 90 cultivated crops," he says. But there are an estimated 4,000 to 5,000 species of native bees in the continental United States--including bumblebees, carpenter bees, sweat bees, leafcutter bees, alkali bees and mason bees such as the blue orchard bee--that also play an important role. Many of them are specialists that pollinate a single plant species within short distances of their nests. This makes their work focused and fast: Four blue orchard bees can pollinate one apple tree in the same time as hundreds of honeybees. Besides being fast and efficient, many specialists perform their magic early in spring when the honeybees are not as active.
But the native bees and other pollinators are suffering from the effects of human disruption of their habitats, according to Buchmann and Gary Paul Nabhan, his collaborator on The Forgotten Pollinators. One of the major reasons for their decline is loss of native plant habitat to shopping malls, business corridors, parking lots and housing developments. Another factor is the extensive use of pesticides (which often kill pollinators as well as pests) on farmlands, in suburbia and in woodlands. In addition, native vegetation and prairies filled with wildflowers (which many native pollinators depend on to feed themselves and their young) have been replaced with pasture grasses for cattle ranching and vast plantings of single-species crops.
All of these actions have resulted in broken "nectar corridors" and habitat fragmentation. Nectar corridors are used by migrating pollinators such as bats, butterflies and hummingbirds. When the pollinators come to an unnatural break in the corridor they move on quickly, arriving at the next group of plants before the flowers have opened and produced nectar. "Now, pollinators have to island hop' across patchy habitats that contain little or no food and dangers [of] highway traffic and pesticide applications," says Buchmann. These fragmented habitats may also be too small to support additional food sources and too far apart to allow for the interchange of pollen. The result of this disrupted interaction is that the plants can't survive without the pollinators and the pollinators (especially specialists dependent on one plant species) can't survive without the plants.
Where native pollinators are suffering from excessive use of pesticides and habitat loss, feral honeybee populations in many states have experienced more than 50 percent losses due to parasites and diseases. Chief among the parasite culprits are two blood-sucking mites--the tracheal mite and the varroa mite--introduced into the United States in the 1980s. Feral European honeybees are also being displaced by aggressive Africanized honeybees, which can take over hives. "They replace the queen with one of their own and in six weeks all the progeny are of African bee stock," says Raymond Williams, an orchard owner in Binghamton, New York, who has been raising honeybees for nearly 50 years.
To help stem the decline of pollinators, Buchmann and Nabhan, director of science at the Arizona-Sonora Desert Museum, recommend that gardeners cut back on pesticide use, create nectar-filled gardens and provide and protect nesting sites. "Home gardeners should, if possible, plant native wildflowers adapted to local/regional soil and climatic conditions," says Buchmann. These and other small steps you can take in your yard can make a big difference for bees, butterflies, hummingbirds and other pollinators. For more details, see "What You Can Do About the Pollination Crisis" and "Create a Pollinator Garden"
Olwen Woodier grows a wide range of native and nonnative plants for bees, butterflies and hummingbirds in her backyard garden in northern Virginia.