Farm pesticide linked to bird declines
Controversial pesticides, which are used “prophylactically” on millions of hectares of Canadian farmland, have now been linked to not only the declines in bees, but also birds.
A Dutch study released Wednesday provides the strongest evidence yet that neonicotinoids are harming insect-eating birds like swallows, which are in sharp decline.
The study, and a second report showing how the chemicals “impair” bumblebees’ foraging skills, add fuel to the charged debate over the pesticides that have exploded in use across Canada in the last decade. While some environmental groups are calling for a national ban, other critics say the federal government should follow Ontario’s lead and restrict their use.
“It has to be reined back, there has to be some common sense here,” says toxicologist Pierre Mineau, a retired Environment Canada research scientist, now working as a consultant for groups such as the American Bird Conservancy.
“It’s a good insecticide,” Mineau says of the neonicotinoids that are used “prophylactically” on corn, soy and canola to prevent insect damage. “The problem is, it is too good. You don’t need to kill every insect in the field 24/7.”
Neonicotinoids are neurotoxins that are especially lethal to insects. They are used to “dress” or coat seeds and are absorbed by plants as they grow, spreading minuscule amounts throughout plant tissues, including in their flowers’ nectar and pollen. The pesticides can also blow off into the environment while farmers are seeding and research shows much of it ends up in soil and contaminating waterways and wetlands.
The Dutch study links use of imidacloprid, one of the most common neonicotinoids, to declines in insecteating birds on tulip farms.
On farms where imidacloprid concentrations in surface water were highest — more than 20 nanograms per litre — bird populations declined by 3.5 per cent on average annually, says the study led by Caspar Hallmann at Radboud University.
He and his colleagues say the problem does not appear to be that the pesticides are toxic to birds, but rather that they are depleting the birds’ food supply by killing off so many insects.
The study, in the journal Nature, concludes that neonicotinoids appear to pose an “even greater risk than has been anticipated” and warns of “potential cascading ef- fects” on ecosystems.
Mineau says the study “looks pretty convincing.” And he notes that the concentration of neonicotinoids associated with the bird declines in Holland are often exceeded in waters on farms in the U.S. and Canada where many insecteating birds are in serious trouble. It’s been estimated that Canadian populations of barn swallows and chimney swifts that swoop through skies devouring bugs are down by up to 75 per cent since 1970.
In Canada, almost 11 million hectares of canola, corn seed, soybeans and cereals are planted each year with seeds treated with neonicotinoids, often referred to as neonics. Ontario is now moving to limit the blanket use of the pesticide and is proposing a system that will require farmers to apply for permits to plant seed treated with neonicotinoids.