Neonicotinoid pesticides are among the most common chemicals used in farming and home gardening. They are considered harmless to people and other mammals, but they attack the nervous systems of insects. Many seeds are sold pre-coated with these pesticides so that the plants have protection before they even sprout. This class of chemicals is successful both in the sense that they’re highly widely used and strong revenue generators for the companies who make them. However, they’ve long been suspected as one of the primary reasons for the decline in the number of honeybees.
But Mother Jones is reporting on new studies that show the danger of ‘neonics’ goes well beyond just insects.
Lots of bird species scavenge seeds for their meals. And these days, many of those seeds are coated in neonics. In a study published last fall, Canadian researchers dosed white-crowned sparrows—a seed-eating, migrating songbird—with the insecticides at various levels. They found that just four seeds coated with imidacloprid, consumed over three days, was enough to cause “significant declines in fat stores and body mass” in the bird and a reduced ability to navigate.
An article on Audubon reaches the same conclusions about the danger to birds. And they found that these pesticides linger in the environment for years.
A 2015 study by the U.S. Geological Survey found neonics in 63 percent of water samples taken from 48 streams. In Canada, researchers detected at least one neonic—there are seven types on the market—in 91 percent of wetlands. Unlike many liquid pesticides, neonics can persist and accumulate in ponds for months, if not years. In other words, says the Center for Food Safety, a nonprofit that promotes sustainable agriculture, neonics are “almost tailor-made to contaminate the environment.”
Their use as seed coatings is highly attractive, as farmers feel it reduces or in some cases even eliminates, the need for spraying. This drops the perceived use of pesticides and does help to eliminate the initial spillover of chemicals from farm fields to neighboring regions. But the persistence of neonics in soil and water shows that the pesticides are still spreading far beyond the locations where they’re used, and killing far more than just the insects that eat crops.
The threat to bees goes beyond theory.
A series of devastating papers published in Science magazine last year showed just how harmful neonics are to the pollinators that are essential to the fresh fruits and vegetables we grow. In one, a team of Swiss researchers found traces of the chemicals in 75 percent of honey samples drawn from around the world—and 86 percent of the samples from North America.
And even though they’re a threat to both birds and bees, they have another problem — though many farmers would swear they’re effective, and the companies that sell them tout their efficiency — neonicotinoids simply don’t work very well against their intended targets.
The chemicals don’t appear to boost crop yields for farmers who use them. That assessment is consistent with 2017 paper from Purdue University researchers, which found “no benefit of the insecticidal seed treatments in terms of crop yield” to US corn growers. Then there’s this 2014 paper by EPA scientists and economists, which revealed that for US soybean farmers, “most usage of neonicotinoid seed treatments does not protect soybean yield any better than doing no with pest control.”
So farmers will spend millions this spring for seeds coated in a chemical which doesn’t increase their yield, but which does spread through the ecosystem to impact beneficial insects and migrating birds.