Pollination is a delivery system, in essence, and like its counterparts in the business world relies on various transportation options. Sometimes, though rarely, pollen is carried by water. Ground delivery by beetles and other land creatures is used to a limited extent, while air travel—via wind, insects, birds, and bats—is by far the preferred mode of transit.
A billion or so years ago, pollen normally reached its destinations by water, but less than 0.1 percent of all plants rely on this method today. Algae and mosses are among the most familiar water-pollinated species. Wind pollination is much more prevalent, employed by more than eight percent of flowering plants such as grasses, conifers, and other trees. Most wind-pollinated species produce more pollen than animal-pollinated plants and have devised mechanisms to prevent the release of pollen under perfectly still conditions. To boost the chances of successful pollination, these plants often have large stigmas (the sticky part on top of pistils) for trapping pollen. In addition, many plants, including pine trees and jojoba shrubs, are aerodynamically designed to siphon pollen from the wind.
But wind pollination is a hit or miss affair, especially as distances increase, and its effectiveness is mainly confined to plants growing in thick stands. Animals, on the other hand, can deliver pollen to isolated plants with great reliability, even after making sizable journeys. More than 80 percent of flowering species depend on animals for "door-to-door" pollen delivery—a customized approach that allows a variety of flowering species to live side by side.
Although bees are the best known, and most important, pollinators, they are by no means the only ones. An exhaustive list would fill a large volume, representing a broad swath of the animal kingdom from ants and flies at the miniature end to bulkier creatures like flying foxes, lemurs, and possums. As in any workable delivery system, these couriers have to be paid. While feasting on a nectar treat, the animals inadvertently pick up pollen and carry it from plant to plant. They're rewarded for their efforts, while advancing nature's grand scheme.
More than 80 percent of the world's 250,000 flowering plants depend on animal pollinators, and roughly 15 to 30 percent of the food eaten throughout the world comes from plants pollinated by these creatures.