Study Showing 75 Percent Insect Decline Suggests Pesticides as a Possible Cause | WYPR

Study Showing 75 Percent Insect Decline Suggests Pesticides as a Possible Cause

Nov 1, 2017

Credit San Antonio Express News

Biologists have long known that Monarch butterflies have been in sharp decline since the late 1990s. A  likely culprit is the increased spraying on farms fields of a weed killer, called RoundUp, which kills the milkweed plants that monarch caterpillars depend on as their sole food source.

At the same time, scientists have documented a decline in bees and other pollinators.  The causes of the bee collapse are likely complex. But again, one factor frequently discussed is modern industrial-style agriculture, which relies on large volumes of pesticides.

These conclusions, however, raiseda logical question:  Of course we take note of what’s happening with large, colorful butterflies and bees. Everyone, even children, notices them – and lots of scientists monitor their populations as their full time jobs.

But what about all the millions of species that are so obscure that nobody studies them or even thinks about them?  An answer to that question was recently published in a scientific journal called the Public Library of Science (PLOS Online).  Ecologist Caspar Hallman and colleagues documented a 75 percent decline in all flying insects over three decades across Germany. They counted bugs trapped in wildlife preserves surrounded by farm fields – and concluded that the pesticides sprayed on the farms is a possible cause.


Scott Hoffman Black is a director of the Xerces Society, a nonprofit dedicated to protecting invertebrates.

 “We should really care about this study and all the studies that show a decline in insects, because insects and the plants that they pollinate are really the fabric of the planet,” said Black.  “You know, if you like to eat salmon, you can thank a small fly that lives in the small stream where that salmon was born.   If you like to listen to songbirds or look at them in your back yard, these song birds are eating insects.  And without these insects, we are going to see – and maybe already are – a decline in our song birds.”

Michael Raupp is a professor of entomology at the University of Maryland.  He said the German study has profound importance for life here in the Chesapeake Bay region and elsewhere around the globe.

“It’s a little bit like Yertle the Turtle,” said Raupp. “Once Yertle moves out from the bottom of the stack, the entire pyramid collapses.  So the loss of plants translates into the loss of critical insects that are then food for all of the members higher up in a food web or food chain.”

Lincoln Brower, a research biologist at Sweet Briar College in Virginia, said that there is a likely solution to this problem.  For generations, farmers and gardeners grew food without chemicals like RoundUP and neonicitinoids.  He said it’s time we recognized that modern monoculture agriculture – although productive -- is sterilizing farm land by eliminating all species that do not serve people. This will eventually have unintended consequences that people may not like, Brower predicts.

“This spraying business needs to be much more carefully controlled than it is,” Brower said. “And there needs to be rules and regulations that are really followed by the farmers.  So that some of the insecticides don’t get into the environment, which is supposed to be free of them.”

Two years ago, Maryland lawmakers made it the first state to impose restrictions on homeowners’ spraying of neonicitinoid pesticides.  The question now is whether such restrictions should now be expanded over more land – including farmland -- and more chemicals now that more information is available.