Flowers Are Losing Their Smell

April 16, 2008 — -- Air pollution is killing the smell of flowers, possibly eliminating the "scent trail" that helps guide those terribly important pollinators, like bees, to the plants that depend upon them for survival, scientists believe.

The discovery could be one of several factors in the "colony collapse disorder" that is wiping out honey bees around the world.

While it is still too soon to determine the full impact of air pollution on the symbiotic relationship between insects and the flowers they pollinate, researchers at the University of Virginia are confident they have shown that pollutants are killing the scent trail, and that could turn out to be extremely significant.

Before the industrial revolution, the trail extended at least half a mile from the flower, but today at that distance "it's almost completely destroyed," said Quinn McFrederick, a doctoral candidate in biology at the university and lead author of a study that in the current issue of the journal Atmospheric Environment.

Scientists have known for some time that airborne chemicals like ozone, hydroxyl and nitrate radicals -- major components of smog -- alter the chemicals produced by flowers that give them a specific smell. But it had not been known how that affected the trail that helps lead insects to the flowers.

Scents that could travel for more than half a mile in the 1800s now probably travel less than about 600 feet, according to Jose D. Fuentes, professor of environmental sciences at the university and a co-author of the study.

"This makes it increasingly difficult for pollinators to locate the flowers," Fuentes said.

In a telephone interview, McFrederick said that the scent trail deteriorates even very close to the flowers, and that could discourage insects, especially bees and moths, from even sampling the flower to see if it contains the nectar they need for survival. And if they pass up the flower, it will not receive the pollination it needs. So both the pollinator and the pollinated suffer.