The indiscriminate use of DDT in the mid-20th century helped nearly exterminate America’s national symbol, the bald eagle, and the pesticide itself became a symbol of an industrial society at war with nature.
Now, more than 40 years after the United States Environmental Protection Agency banned DDT, thanks in large part to the publication of Rachel Carson’s Silent Spring, a class of agricultural pesticides called neonicotinoids (neonics) poses an even more serious threat to bees, other wildlife, and entire ecosystems, according to a preview of a report to be published next week by an international group of scientists.
“In the case of acute effects alone, some neonics are at least 5,000 to 10,000 times more toxic to bees than DDT,” wrote the scientists affiliated with the Task Force on Systemic Pesticides. “The evidence is also clear that neonics pose a serious risk of harm to honey bees and other pollinators.”
Studies have implicated neonics in the mass die-off of bees that pollinate a third of the global food supply. Many scientists believe the pesticide is one of several interrelated factors—including disease, parasites, and poor nutrition—responsible for the apian catastrophe that has unfolded over the past decade.
The task force analyzed more than 800 peer-reviewed studies that investigated the impact of neonics and an insecticide called fipronil on insects like bees, mammals, birds, and reptiles. Neonics and fipronil have become pervasive in the environment over the past two decades and now account for 40 percent of the global pesticide market, according to the report.
Neonics and fipronil belong to a class of so-called systemic pesticides that are absorbed into a plant’s roots, stems, leaves, flowers, pollen, and nectar. Farmers can spray plants with neonics, but seeds are now routinely treated with the chemical, meaning that as the plant grows the pesticide remains part of the flora.
And increasingly the fauna.
“The combination of persistence (over months or years) and solubility in water has led to large scale contamination of, and the potential for accumulation in, soils and sediments, ground and surface water and treated and non-treated vegetation,” the scientists wrote. “The effects of exposure to neonics range from instant and lethal to chronic. Even long term exposure at low (non-lethal) levels can be harmful.”
Neonics are nerve poisons, but the effects extend beyond the pests the pesticide is intended to kill, according to the report, damaging bees’ ability to forage and fly and increasing their susceptibility to disease. They are less harmful to birds and mammals but can have indirect consequences, such as killing off insects those animals eat.
Still, the scientists acknowledged that what they don’t know about neonics far exceeds what they do know. For instance, tests to determine neonics’ toxicity have only been done on four of 25,000 bee species, and few toxicological studies have been carried out on other pollinators, such as butterflies.
And 96 percent of those studies have been performed in the laboratory under controlled conditions. How neonics affect the behavior of bees and other wildlife remains largely unknown.
The full report will be published next week in the journal Environment Science and Pollution Research. But the scientists left no doubt about their conclusions.
“The current extensive use of this group of persistent highly toxic chemicals is affecting global biodiversity,” the report’s authors wrote, urging governments to regulate neonics more strictly and to begin a worldwide phaseout. “Their continued use can only accelerate the global decline of important invertebrates and, as a result, risk reductions in the level, diversity, security and stability of ecosystem services.”