Scores of studies have established that neonicotinoids, the most widely used pesticides in the world, are contributing to the steady decline of bees and other insects across North America and Europe. Now evidence is growing that these compounds, tailored to take out invertebrates, can also harm mammals, birds and fish, as Elizabeth Royte explains in FERN’s latest story, published with National Geographic.
“[S]cientists have found that only about 5 percent of neonic seed coatings are taken up by crop plants,” Royte writes. “The rest washes or wears off seeds. The chemicals accumulate in soils and waterways, where a wide range of wildlife is exposed to them.
“Exactly how neonic-coated seeds affect growth, development, and organ function of vertebrates remains an open question. But evidence of harm is accumulating. Researchers in Canada have shown that consuming as few as four imidacloprid-treated canola seeds over three days can interfere with a sparrow’s ability to migrate. A graduate student at South Dakota State last year demonstrated that ring-necked pheasants—the number-one game animal in the Dakotas—became more underweight, weak, and lethargic the more treated corn seeds they consumed. (According to the researcher, the birds were fed fewer treated seeds than they’ve been observed to eat in the wild.) Higher-dosed birds also laid fewer eggs, started their nests a week later, and suffered a 20 percent decline in chick survival.
“Lab studies have reported a slew of evidence that exposure to neonics is harmful to vertebrate animals. It reduces sperm production and increases abortions and skeletal abnormalities in rats; suppresses the immune response of mice and the sexual function of Italian male wall lizards; impairs mobility of tadpoles; increases miscarriage and premature birth in rabbits; and reduces survival of red-legged partridges, both adults and chicks.”