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Pollen Nation

One-third of the world's food supply consists of fruits, nuts, seeds, and vegetables. In the United States, this translates to an estimated worth of around $8 billion annually. This does not even take into account the wood, natural fibers, spices, and medicines that come from plants. Most people have not considered the fact that without pollination, these important resources would cease to exist.

There are 821 species of gymnosperms (such as pines, firs, and ginkgos) and around 250,000 species of angiosperms (flowering plants) worldwide. They all depend on pollination in order to produce seeds and fruit, and thereby to reproduce. The pollen must somehow be transferred (by some vector) from the male parts of the plant to the female parts. This is accomplished in a variety of ways.

Evergreens and most grasses rely on wind for their pollination. This is especially effective in habitats with large stands of the same plant, and where there is a consistently windy climate, such as grasslands and savannahs. There are plants that rely on gravity, some on rain, and some, in aquatic habitats, on the movement of water.

Other plants have evolved to take advantage of more sophisticated means of transport. In habitats where there is a great diversity of plant species the problem of getting the correct pollen to the correct plant becomes more difficult. An extreme example of this is the tropical rainforest. There may be hundreds of species in a given acre and the next individual of a particular species may be quite some distance away. This is where animal vectors come in.

Scientists estimate that there are somewhere between 100,000 and 200,000 species of animals that plants rely on for pollination. For most people, bees and butterflies come to mind first but there are many other types of insect pollinators. The list is long, but includes lacewings and many species of beetles, flies, and wasps. There are also birds, mammals, and even reptiles that pollinate flowers. Each flowering plant has evolved to attract a particular vector. Which animal is attracted depends on the color, smell, and shape of the flower.

Bright reds and yellows attract butterflies and hummingbirds, especially the contrast between the two colors. Even a red baseball cap can attract a hummingbird for a closer look. Moths and bats, which feed at night, are drawn in by white or very light colors. An example is the lesser long-nosed bat, found in the deserts of northern Mexico. It is the only pollinator of the cardon, the world's largest cactus at up to 60 feet tall. The bat feeds on the cactus' nectar with a tongue as long as the bat's entire body. Besides the nectar-eating bats, fruit bats such as flying foxes are also pollinators.

Flowers that attract mammals often have a strong odor and are usually brown or white. The plants also tend to be sturdy, so they can bear the weight of their visitors. In Madagascar the black lemur, a small mammal with a long tongue, drinks the nectar of the trail palm. The lemur then spreads pollen by jumping from palm to palm.

There are an estimated 40,000 species of bees in existence. These pollinators are attracted by colors at the blue end of the spectrum, towards ultraviolet. They will also visit flowers in the red color range, but this is probably because they are seeing near-ultraviolet patterns that humans cannot. Some bees are attracted by scent, such as that of certain orchids that look and smell like a female bee. The male bee will try to mate with these flowers, transferring pollen in the process.

Honeybees are very useful to humans-they evaporate nectar to produce honey, and make beeswax, which is used for candles, polishes, inks, and cosmetics. Most importantly, honeybees are the primary pollinators of commercial food crops. Apple farmers have found a direct correlation between the size and shape of their fruit and the number of bees and other pollinating insects. The more seeds an apple holds, the bigger the size and more symmetrical the shape. In the southeastern U.S., highbush blueberry farmers depend on wild southeastern blueberry bees for pollination. Each female blueberry bee can pollinate four to five gallons of rabbit-eye blueberries during her lifetime. Based on the commercial value of blueberries, some farmers see these bees as flying $50 bills. These examples barely scratch the surface of the importance of honeybees.

Honeybees, however, are declining both in the wild, where they are almost extinct in some places, and in domestic stocks, where up to one third of all hives have been lost. This decline in population is caused by the destruction of nesting and feeding sites for development and the use of pesticides, which kill other beneficial insects as well. Domestic bees, kept together in masses, are vulnerable to diseases and pests accidentally introduced by humans. Scientists around the world have observed this negative trend and are working on ways to protect all flower pollinators. Unchecked, this trend will affect us all because we are a "pollen nation."