Imagine a world without fruits, vegetables or flowers. That's what our world would be like without pollinators-animals that pollinate our plants. Three-quarters of our flowering plants rely on insects, birds or bats to move pollen from the male to female parts of flowers for reproduction.
Most plants need to make seeds to reproduce. But many can't do it by themselves. To make seeds, the female part of the plant, called a pistil, needs pollen from the male part of the flower, called a stamen.
Cross-pollination is the rule of thumb in the plant world. This means that not only does pollen have to be transported from stamen to pistil but it also must come from separate flowers. Some plants rely on the wind to do this. Many others depend on insects and other animals. Pollinators use the nectar from flowers for food. Many, like bees, get sticky pollen grains on their bodies and transfer it to the pistils when they move from one flower to another.
More than 100,000 animal species-and perhaps as many as 200,000-pollinate 250,000 kinds of flowering plants. Insects-bees, wasps, moths, butterflies, flies, beetles-are the most common pollinators, and as many as 1,500 species of other animals including hummingbirds, perching birds, flying foxes, fruit bats, opossums, lemurs and even a gecko help to move pollen from plant to plant.
Pollinators are critical to both our ecosystem and our economy. Honeybees alone are responsible for an estimated $15 billion worth of pollinator services to agriculture in the United States. Most fruit, vegetable and seed crops, as well as crops that provide fiber, drugs and fuel, are pollinated by animals. We are not the only animal whose diets include animal-pollinated food. Many birds and mammals depend on fruits and berries for food.
Plants often help their specific pollinators find their way. This co-dependence is exhibited in many ways.
Many night-pollinated flowers close during the day to prevent thieves from getting at their nectar and pollen. Many daytime-pollinated flowers close at night for the same reason. Flowers pollinated at night are usually white or pale yellow and very fragrant. This helps to announce the flowers' presence. Darker flowers, not as visible at night, are usually pollinated by day-flying insects.
Bees prefer blue or yellow flowers and those that are sweet-smelling. Butterflies rely more on vision and less on scent to find nectar. They are attracted to red, yellow or orange flowers. Moths are attracted to sweet-scented flowers that are typically large and white or pale in color, Hummingbirds go for red, orange or yellow flowers.
Flowers assist the pollinator in finding where the pollen or nectar is stored. Flowers often have bee lines-dots or color variations that direct the pollinator. Flowers have many shapes: bowl, cup, star or tube. Shapes are specific to pollinators and, in some cases, also keep out unwanted pollen collectors.
Despite their importance to our economy and our lives, many pollinators are in trouble. Honeybees (Apis mellifera), raised specifically to pollinate crops, are in decline. Causes include parasitic mites, disease, pesticide poisoning, the encroachment of Africanized honeybees and a phenomenon, Colony Collapse Disorder, where the bees leave the hive in search of nectar and do not return. Many farmers depend on honeybees, leasing them during specific seasons to pollinate targeted crops. Declines in these managed pollinators can affect the availability, price and quality of the fruits, vegetables, and other products that depend on animal pollination.
The causes of decline in wild pollinators vary by species. Like the honeybee, the bumblebee has been hurt by the introduction of a non-native parasite carried by bumblebees imported from Europe for greenhouse pollination. Other pollinators are affected by habitat loss or fragmentation such as the destruction of cave roosts for some bats. The disturbance of migratory routes also disturbs populations of hummingbirds, nectar-feeding bats and some butterflies.
A healthy ecosystem provides pollinators with habitat for foraging, nesting, roosting and mating. Meanwhile, homes, businesses and roads are replacing the native fields, wetlands and forests that are home to many pollinators. In addition, many of the wildflowers used by pollinators for food, nesting or egg-laying are rapidly disappearing.
Pesticides are also a threat. Many pesticides used on farms and backyard gardens are broad-spectrum types, meaning they can harm non-target species. Often, insecticides that get rid of plant pests are toxic to bees and other beneficial insects.
Migrating pollinators such as bats, butterflies and hummingbirds face even more problems. They need nectar-producing flowers all along their journeys. But wildflowers and natural habitats are being replaced by development, decreasing the amount of food and habitat that is available.
Pollinator Week is June 21-June 27, 2010. Go to www.pollinator.org for information on events, activities and resources.
To learn more about pollinators:
- Visit www.fws.gov/pollinators/
- Read the National Academy of Sciences report, Status of Pollinators in North America, at http://dels.nas.edu/pollinators/
- To help pollinators:
- Reduce the use of pesticides or, if possible, stop using them altogether. If one must use an insecticide, apply it in the evening, when many pollinators are inactive.
- Plant native, nectar-producing flowers. Go to http://pollinator.org/guides.htm and type in your zip code to receive information about pollinators in the area, plus a list of pollinator plants.
- Leave tree stumps, dead branches and rotting trees on your property, if possible. They provide nests for some species of bees.
- When a bee nest is too close to one's home, don't destroy it. Contact a local beekeeper or state cooperative extension service to learn how to remove it without harming the bees.