Over the years, butterfly population declines have been cited due to habitat loss, climate change and pesticides. A new study co-authored by MSU professors finds that insecticides have had a significant impact on populations.
Published last month, it included authors Braeden Van Deynze and MSU professors Scott Swinton and Nick Haddad, and analyzed 17 years of survey data across 81 counties and five states in the Midwest to come to this conclusion, according to the survey.
“I was able to get access to extremely detailed survey data from 1998 to 2014,” Swinton, a professor of Agriculture, Food and Resources at MSU, said. “We had detailed information on the chemicals that they were using, farming practices, the kinds of seeds they were using and I recognized this was a terrific opportunity to look at long term effects on other aspects of the ecosystem affected by agriculture.”
Haddad, a professor in the department of Integrative Biology, said in the Midwest, butterfly populations are declining by 2% every year, with over a quarter of all species in significant decline.
Haddad said most studies will state that the population of butterflies is declining and state that it is likely related to climate change, habitat loss or pesticides, but never go further.
“This is, in my view, one of the greatest scientific mysteries of our time, because butterflies and other insects being lost so fast has to have consequences for ecological systems,” Haddad said.
With the data collected over this 17-year period, Haddad said that they were able to make comparisons far easier due to this accessibility.
“Now we’re able to compare apples to apples to apples: climate, land use, pesticides; and ask which rises to the top as the cause of butterfly decline,” he said.
Over this time period, Haddad said that insecticides were responsible for an 8% loss in the number of butterflies as well as butterfly species.
“When dealing with insecticides, there are many classes and the one that rose to the top is a new, especially toxic class called neonicotinoids,” he said.
Neonicotinoids are a class of synthetic, neurotoxic insecticides used on crops and are the most popular class of insecticide in the United States, according to the Natural Resource Defense Council. They can be applied directly to the soil, or on a plant’s seed, which makes the entire plant toxic as it grows to any insects.
“They get into the environment, in part, in the planting stage,” he said. “Dust is created as the seeds are tumbling down into the soil and that dust gets into the air and then settles on nearby habitats.”
Word is getting out there, however, Haddad said. Many countries in Europe have restricted the use of them and areas in Canada like Quebec have adopted a prescription system for these insecticides. Here, farmers can use them whether or not they are needed. With this system in Quebec, farmers can only use the treatment if they have demonstrated a genuine pest problem.
Avoiding the use of these insecticides can be tricky, however.
“Farmers now hardly have a choice to use them,” Haddad said. “They’re almost on every seed, and they’re just sold with pesticides on them. From the farmers I talked to, if they were given another choice they might go a different direction and not use coated seeds.”
Butterflies are great indicators for what is happening, he said, as well as pollinators in general and other species that have such great impact on a sustainable environment.
Additionally, Swinton said the comprehensive 17-year pool of data they used for the study does not have any easily accessible counterparts for the present. Collecting new data would be incredibly expensive.
Newer data with the same level of comprehensiveness is very attractive, as farmers continue to develop new technologies, not included in the data used previously.
“Unfortunately, the U.S. government, through the U.S. Geological Survey, stopped collecting data on certain pesticides, including neonicotinoid seed treatments, in 2015, the year after our study,” Swinton said.
When addressing these insecticides, Swinton said care must be taken.
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“We have to be careful in making these choices because pesticides are important tools,” he said. “They are like medicines, you don’t want to overuse them, but if used right, they play very important roles.”
Swinton summarized the conclusion of their research as a story of "unintended consequences."
"Neonicotinoid seed treatments were developed by agricultural companies as an answer to the problem of soybean aphid (insect pest of soybean plants) losses, and it was successful," Swinton said. "It sharply eliminated losses to soybean aphid in the Midwest, but we’ve had unexpected effects on non-target species, and in particular butterflies. The message here is that it's important to manage these chemicals carefully, like medicines."
