Pollination Services: No Food Without Them
If you tended or visited a flower garden or you visited one this summer, you know it' s a favorite spot for bees, butterflies, and other insects. If you're lucky, you saw hummingbirds dipping elegant bills into tubular flowers. All of these pollinators are attracted to the flower's nectar, the sweet, energy-rich food produced by many flowering plants. The insects, birds, and even bats do plants a favor, too, when they stick their heads and bodies into the flower for that nectar -- they get pollen all over themselves. As these animals move from flower to flower, they transfer pollen, fertilizing future seeds and fruits, helping to produce future generations of plants.
Pollination is one of nature's services often taken for granted. Think about that last fast-food meal you picked up for lunch: hamburger, French fries, and a strawberry milkshake. The cattle that contributed to the hamburger and produced the milk in your shake probably ate alfalfa hay. Alfalfa flowers are pollinated by several species of bees. Although animals don't need flowering alfalfa hay, pollinated flowers are needed to produce alfalfa seed. The wheat in the bun was pollinated by the wind, but everything else on that bun required an animal pollinator. Bees pollinated the mustard plant, tomatoes in the ketchup, the cucumbers that were made into pickles, and the black pepper. In addition to bees, flies and other small insects pollinated the onions and lettuce layered on your burger. Bees, flies and wasps helped pollinate the plants from which many of the oils used for frying potatoes come. Bees also pollinated the sugar cane that sweetened your milkshake and the strawberries used for flavoring. If you had coffee or tea with that meal or for breakfast, bees and flies tended to those flowers too.
Obviously, we depend on pollinators for much of our food. Researchers with the Forgotten Pollinators Campaign, based in Tucson, Arizona, estimate that one in every three bites of food is made possible by a pollinator. Approximately two-thirds of the crops grown around the world require animal assistance for pollinating their flowers. Pollinators also are essential for maintaining plant populations throughout the world. Of the approximately 240,000 species of flowering plants with known pollinators; nearly 220,000 of those are pollinated by animals. The rest rely on water or wind.
Until recently, we accepted pollination as one of nature's free services. Native and locally managed European honeybee colonies, which are an introduced species, provided this service for many of North America's crops. Since 1947, however, the European honeybee colonies that commonly pollinate US agricultural crops have declined by 50 percent, due to diseases, pesticides and habitat loss. Although it is difficult to estimate the monetary loss to consumers due to declining pollinator populations that result in inefficient crop production or outright crop failure, annual losses may run as high as $5.7 billion-$8.3 billion. Those losses could be reduced to $1.6 billion per year, if native and introduced populations of pollinators can be substituted for declining native and European honeybee populations. To avert such losses, almond growers in California are investing in "replacement pollinators." In 1999, growers trucked in over 900,000 bee colonies to pollinate their almond crops.
A native bee of the San Rafael Desert, Osmia sanrafaelae, shows potential as a pollinator of commercial alfalfa and may help fill the gap left by the declining honeybee population. More research is needed, however, before this desert-dweller is available to growers. In the meantime, alfalfa leafcutting bees, Megachile rotundata, brought from Europe to North America in the early 1900's, are pollinating alfalfa seed crops in western North America. Leafcutting bees prefer alfalfa to other plants and are used extensively in Washington, Oregon, Idaho, Montana and Nevada, where they help produce alfalfa seed on over 61,500 acres. The estimated value of the region's population is just under $11 million.
Insecticides used to kill agricultural pests also kill beneficial pollinators. In Eastern Canada, nearly 70 species of native insects, including many species of bumblebees, pollinate commercial lowbush blueberry plants. Between 1969 and 1978, fields beside blueberry fields were sprayed with an insecticide used to control spruce budworm. During that decade, local bumblebee populations declined and lower blueberry crop yields resulted. After the original insecticide was replaced with a narrower spectrum insecticide that didn't kill bees, native bee populations steadily recovered.
Many pollinators, such as birds, bats, and butterflies, migrate long distances. These pollinators depend on nectar-producing flowers as they travel. Four migratory pollinator species that fly the "nectar corridors" throughout western Mexico and the southwestern United States are under study by the Forgotten Pollinators Campaign. Researchers suspect habitat fragmentation due to human development, herbicide destruction of roadside and fieldside plants, and the introduction of exotic plant species may affect the ability of the white- winged dove, lesser long-nosed bat, rufous hummingbird, and monarch butterfly to survive migration and pollinate plants along their route. At the same time, native plants along those migration routes require the assistance of pollinators to increase genetic mixing, seed set and reproduction.
Although it is difficult to put a monetary value on the services provided by all pollinators, it is fairly easy to imagine a world without these beneficial creatures. No flowering plants and food shortages would make it almost impossible for humans to survive. To date, no technological fix exists that would replace all natural pollination. Since pollinators depend on native plants and habitats to live and feed, only with these natural supports can they tend to the agricultural crops on which we depend.
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