Pollution Impedes Bees' Crop Pollination

"Bees and butterflies play a vital role in agriculture, with farmers around the world depending on these and other insects to help pollinate crops ranging from coffee and cocoa to berries. But new research from the U.K. shows that common air pollutants can interfere with pollination and thus the cultivation of crops by making it hard for some insects to sniff out the aromatic flowers where they sip nectar and nosh on pollen.

"Diesel exhaust and ozone pollution can react with the chemicals that make up the floral odors that insects use to find flowers," said James Ryalls, a University of Reading research fellow and the lead author of a paper describing the research published Wednesday in the journal Environmental Pollution. "It can just make them not smell anything at all."

The insects' ability to find flowers was impaired even at pollutant concentrations below the range deemed dangerous by U.S. law, the research showed.

"The results are important because they show that legislatively 'safe' levels of pollution can deter pollinators," said Shannon Olsson, a National Center for Biological Sciences professor at the Tata Institute of Fundamental Research in Bangalore, India. She wasn't involved in the research.

Pollinators play a role in up to $577 billion worth of global crops cultivated each year, according to a report issued in 2016 by the United Nations' Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. At least 70% of crop species rely on insect pollination, Dr. Ryalls said.

Previous research on the effects of air pollution on pollinators often relied on laboratory findings. But Dr. Ryalls and his colleagues looked at the effects of pollutants in a real-world setting. At the university's farm in Sonning, west of London, they planted black mustard plants within eight 26-foot-wide zones bordered by perforated pipes set up to spew nitrogen oxides -- gaseous compounds found in diesel exhaust -- and ozone, a principal ingredient of smog.

Then they flooded two of the zones with diesel exhaust, two with ozone and two with both pollutants -- leaving two areas untreated. In the zones treated with a single pollutant, the pollution levels were about half the maximum safe level as specified under current U.S. Environmental Protection Agency outdoor air quality standards.

During the summers of 2018 and 2019, the researchers observed the numbers and type of pollinators that visited the flowering plants in polluted and unpolluted zones. They found that plants within zones with polluted air received up to 70% fewer visits from insects than those in untreated areas. The reductions in visits brought a 31% decline in pollination along with reductions in the plants' health, as indicated by reduced growth and underdeveloped seed pods.

Reduced pollination also yields lower-quality fruit, according to Robbie Girling, an associate professor of agroecology at the University of Reading and a co-author of the study. "If fruits like apples and strawberries don't get enough pollination, you end up with deformed fruit," Dr. Girling said." [1]

1. U.S. News: Pollution Impedes Bees' Crop Pollination
Woodward, Aylin. Wall Street Journal, Eastern edition; New York, N.Y. [New York, N.Y]. 20 Jan 2022: A.3.