Insects play an important role in the world’s food production. Roughly 70 percent of all crop species, including apples, strawberries and cocoa, depend on them for pollination.
Insects rely on a flower’s odor to locate a plant, but atmospheric pollutants alter these smells, making foraging more difficult. A new study in Environmental Pollution tested how much of an impact pollution has on pollinators in the field.
Researchers built eight 26-foot-wide octagons in a wheat field and piped treatments of diesel exhaust, ozone, a combination of the two and ambient air into two octagons each. Pollution concentrations were well below what the United States Environmental Protection Agency considers safe under its air quality standards, the study states. The researchers planted 24 black mustard plants that were not yet flowering into each octagon and monitored their pollination.
They found a reduction in insect pollinators by up to 70 percent and a reduction in their flower visits by up to 90 percent. Ultimately, pollination was reduced between 14 to 31 percent, based on seed yield and other factors.
“We weren’t expecting nearly as severe a reduction as we found. It’s kind of crazy,” study author James Ryalls, an agricultural ecologist at the University of Reading in the United Kingdom, tells New Scientist’s Adam Vaughan. “If the results from this study extend to the landscape scale, air pollution is likely a pretty important but underlooked factor contributing to pollinator decline. It’s a bit worrying.”
Populations of bees and other pollinators are declining worldwide because of habitat loss, pesticides, climate change, parasites, and non-native species, per the National Park Service. But agriculture reliant on these insects continues to increase. In 2012, the economic value of insect pollination was estimated at $34 billion in the United States.
“The results [of the study] are important because they show that legislatively 'safe' levels of pollution can deter pollinators,” Shannon Olsson, a chemical ecologist at the Tata Institute of Fundamental Research in Bangalore, India, who wasn’t involved in the research, tells the Wall Street Journal’s Aylin Woodward.
Diesel engines are becoming more efficient, but they still contribute to air pollution. About a third of the United States’ transportation fleet still consists of diesel engines and vehicles, per the EPA.
“Globally, many of the newly approved diesel vehicles sold continue to exceed emission limits, ensuring diesel exhaust emissions will remain a problem for many decades,” the study states.
Diesel fuel is regulated, but it still contributes heavily to air pollution. In 2015, 385,000 people worldwide died prematurely from air pollution from vehicle emissions, with diesel vehicles responsible for 47 percent of those deaths.
“We have to transition away from fossil fuels anyway, and we are,” Ryalls tells New Scientist. “We should be doing it faster.”