Virginia
April 14, 2008
Air pollution from power plants
and automobiles is destroying the fragrance of flowers and
thereby inhibiting the ability of pollinating insects to follow
scent trails to their source, a new University of
Virginia study indicates. This could partially explain why
wild populations of some pollinators, particularly bees – which
need nectar for food – are declining in several areas of the
world, including California and the Netherlands.
The study appears online in the journal
Atmospheric
Environment.
"The scent molecules produced by flowers in a less polluted
environment, such as in the 1800s, could travel for roughly
1,000 to 1,200 meters; but in today's polluted environment
downwind of major cites, they may travel only 200 to 300
meters," said Jose D. Fuentes, a professor of environmental
sciences at the University of Virginia and a co-author of the
study. "This makes it increasingly difficult for pollinators to
locate the flowers."
The result, potentially, is a vicious cycle where pollinators
struggle to find enough food to sustain their populations, and
populations of flowering plants, in turn, do not get pollinated
sufficiently to proliferate and diversify.
Other studies, as well as the actual experience of farmers, have
shown that populations of bees, particularly bumblebees, and
butterflies have declined greatly in recent years. Fuentes and
his team of U.Va. researchers, including Quinn McFrederick and
James Kathilankal, believe that air pollution, especially during
the peak period of summer, may be a factor.
To investigate this, they created a mathematical model of how
the scents of flowers travel with the wind. The scent molecules
produced by flowers are very volatile and they quickly bond with
pollutants such as ozone, hydroxyl and nitrate radicals, which
destroy the aromas they produce. This means that instead of
traveling intact for long distances with the wind, the scents
are chemically altered and the flowers, in a sense, no longer
smell like flowers. This forces pollinators to search farther
and longer and possibly to rely more on sight and less on smell.
The scientists calculated scent levels and distances that scents
can travel under different conditions, from relatively
unpolluted pre-industrial revolution levels, to the conditions
now existing in rural areas downwind from large cities.
"It quickly became apparent that air pollution destroys the
aroma of flowers, by as much as 90 percent from periods before
automobiles and heavy industry," Fuentes said. "And the more air
pollution there is in a region, the greater the destruction of
the flower scents."
The National Science Foundation funded the investigation. |
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