What is a pollinator and why do we need them?

What is a pollinator?
Pollinators are animals (mostly insects, but including some birds and mammals) that facilitate the development of seeds and the fruit surrounding seeds. Humans and other animals need pollinators to produce nuts and fruits that are essential components of a healthy diet. Nearly 90% of flowering plant species found worldwide benefit from animal-mediated pollination to make the seeds that will grow into the next generation of plants [1]. Honey bees often come to mind first when people think of pollinators. However, many other insects (i.e., other bee species, butterflies, beetles, flies), some birds, and some bats are also pollinators.

Pollination occurs when pollen from male structures (anthers) of flowers is moved to the female structure (stigma) of the same plant species. Movement of pollen (analogous to sperm) to a flower's stigma results in fertilization of the flower's eggs. An adequately fertilized flower will produce seeds and the fruit surrounding seeds, ensuring that a new generation of plants can be grown.

Why do we need them?
Pollination is mutually beneficial to plants and to pollinators. While the plants receive pollination ecosystem services, pollinators receive nectar and/or pollen rewards from the flowers that they visit. Sugary nectar provides pollinators with carbohydrates while pollen offers proteins, fats, vitamins, minerals, and necessary phytochemicals. See [2] for a recent review of bee nutritional needs.

Not every species of plant requires animal-mediated pollination services. For example, wheat is wind-pollinated. However, the majority of crops that we like most to eat and provide most of our nutrition (fruits, vegetables, and nuts) use animal-mediated pollination [3, 4]. Without pollinators, our diets would be severely limited, and it would be more difficult to acquire the variety of vitamins and minerals that we need to stay healthy.

The approximately 90% of non-agricultural plants that rely on animal-mediated pollination are the foundation of terrestrial food chains [1]. The leaves and/or fruits and nuts that plants make are eaten by herbivores which in turn are hunted by predators. Furthermore, these plants provide shelter and nesting habitat for many different animal species. Thus, to maintain the diversity of our natural ecosystems, we need healthy pollinator populations to ensure that the next generation of plants will be produced.

  1. Ollerton J, Winfree R, Tarrant S: How many flowering plants are pollinated by animals? Oikos 2011, 120(3):321-326.

  2. Vaudo, A. D, Tooker, J.F., Grozinger, C.M. and H.M. Patch. "Bee nutrition and floral resource restoration." Current Opinion in Insect Science 10:133-141 (2015).

  3. Klein, A-M, et al. "The importance of pollinators in changing landscapes for world crops". Proceedings of the Royal Society B 274 (1608): 303-313.

  4. Eilers, E.J. et al. "Contribution of Pollinator-Mediated Crops to Nutrients in the Human Food Supply" PLoS One 6(6): e21363. doi:10.1371/journal.pone.0021363