Bees and butterflies are baffled by air pollutants, posing a threat to crops

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 UK shows that common air pollutants can interfere with pollination and therefore the growing of crops by making it difficult for some insects to sniff out aromatic flowers where they sip nectar and feed on pollen.

“Diesel exhaust and ozone pollution can react with the chemicals that make up floral scents that insects use to find flowers,” said University of Reading researcher and lead author James Ryalls. of an article describing the research published Wednesday in the journal. Environmental pollution. “It may just prevent them from feeling anything.”

Bees and butterflies primarily rely on their sense of smell to locate flower patches before heading to individual plants by sight. When insects fly between flowers to collect pollen, they can transfer some of that pollen from a flower anther, or male part, to a stigma, or female part. This process helps plants produce seeds and reproduce.

“Insects sense the world as we see it,” said Shannon Olsson, a professor at the National Center for Biological Sciences at the Tata Institute for Basic Research in Bangalore, India, who was not involved in the research. “Their antennae are, for some species, more than a million times more sensitive than the human nose.”

The insects’ ability to find flowers was impaired even at pollutant concentrations below the range deemed dangerous by US law, according to the new research.

“The results are important because they show that legislatively ‘safe’ levels of pollution can deter pollinators,” Dr Olsson said.

Pollinators play a role in up to $577 billion of global crops grown each year, according to a 2016 report by the United Nations Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.

At least 70% of all crop species depend on insect pollination, Dr Ryalls said.

Pollutants were emitted from visible rings to study their effect on pollination at the University of Reading Farm.



Previous research on the effects of air pollution on pollinators has often relied on laboratory results. But Dr. Ryalls and his colleagues looked at the effects of pollutants in a real environment. At the university farm in Sonning, west London, they planted black mustard seedlings in eight 26ft-wide areas lined with perforated pipes installed to spit diesel exhaust and ozone , a main ingredient of smog.

Then they flooded two of the areas with diesel exhaust, two with ozone, and two with both, leaving two areas untreated. In areas treated with diesel exhaust or ozone, pollution levels were about half the maximum safe level specified by current U.S. Environmental Protection Agency outdoor air quality standards. the environment.

During the summers of 2018 and 2019, researchers observed the number and type of pollinators visiting flowering plants in polluted and unpolluted areas. They found that plants located in areas with air pollution received up to 70% fewer insect visits than those located in untreated areas. The reduction in visitation resulted in a 31% drop in pollination as well as reductions in plant health, as indicated by reduced growth and underdeveloped pods.

The research highlights another threat to bee species, which have seen precipitous population declines in the United States and Europe in recent years, in part due to heavy pesticide use, as well as the loss of habitat. Research published in the journal Nature Communications in 2019 found that a third of the 353 species of wild bees and bee-like species known as hoverflies in Britain experienced declines between 1980 and 2013.

The effects of pesticides and habitat loss also extend to other pollinators. Between 2000 and 2009, England lost 58% of butterfly species on cropland, according to a 2019 paper published in the journal Biological Conservation.

“Our results suggest that air pollution is another potential stressor to add to growing pressures on pollinators,” Dr Ryalls said. Bees and other pollinators depend on scents not only to find food, but also to find mates, communicate, and find places to lay their eggs.

If all pollinating insects were to disappear, Dr Ryalls said, grains including wheat, rice, maize and barley, as well as bananas, pineapples and some other fruits, would not be affected. These plants do not depend on insect pollination.

Without pollinators, pumpkins would need artificial pollination methods to grow.


mads claus rasmussen / Shutterstock

Coffee, soybeans, okra, and some other crops that depend in part on pollinators would see lower yields that would likely make them more expensive to grow. And the cultivation of cocoa beans, Brazil nuts and fruits, including melons, kiwis and pumpkins, would only be possible with the use of artificial pollination methods, including people who carefully transfer the pollen instead of insects.

Reduced pollination also results in lower quality fruit, according to Robbie Girling, associate professor of agroecology at the University of Reading and co-author of the study.

“If fruits like apples and strawberries don’t get enough pollination, you end up with misshapen fruit,” Dr. Girling said. “You can’t sell it because nobody wants to buy it, and the fruit doesn’t stay fresh that long.”

Write to Aylin Woodward at [email protected]

Copyright ©2022 Dow Jones & Company, Inc. All rights reserved. 87990cbe856818d5eddac44c7b1cdeb8

About Sherri Flowers

Check Also

Management of small hive beetles in honey bee colonies

Small hive beetles (Aethina tumida) can cause significant damage in commercial honey bee colonies in …