Controversial pesticides, which are used “prophylactically” on millions of hectares of Canadian farmland, have 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 plants’ 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 insect-eating 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 lead 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 effects” on ecosystems.
Mineau say the study “looks pretty convincing.” And he notes that the concentration of neonicotionuds associated with the bird declines in Holland are often exceeded in waters on farms in the U.S. and Canada where many insect-eating 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 up to 75 per cent since 1970.
In Canada almost 11 million hectares a year of canola, corn seed, soybeans and cereals are now planted each year with seeds treated with neonicotinoids, often referred to as neonics. And a recent report by Christy Morrissey at the University of Saskatchewan, and her colleagues at Environment Canada and Agriculture and Agri-Food Canada, revealed widespread neonicotinoid contamination in wetlands and ditches on prairie farms.
The study reported concentrations in Canadian wetlands that were often higher than the levels linked to bird declines in the Dutch study. The Saskatchewan work also showed the chemicals can persist for months, potentially killing off mosquito and midges many birds feed on.
The Canadian team’s research is ongoing and suggests “current agricultural practices and use of neonics in Prairie Canada can negatively affect aquatic insect emergence and birds,” Morrissey said by email.
She describes the Dutch study as a “great contribution” saying “the evidence is growing that neonics are exerting effects beyond the pest species in farm fields and there are real conservation concerns for more species beyond bees.”
In another study released this week scientists report neonicotinoids can impair bumblebees’ ability to learn how to gather pollen.
Professor Nigel Raine, at the University of Guelph, and a colleague in Britain tracked bumblebees using tiny tags and compared foraging skills of bees exposed to neonicotinoids with the skills of unexposed bees.
He says bumblebees normally improve and hone their foraging skills with experience.
“The untreated bees get better, they learn which flowers to visit and they learn how to extract the pollen from flowers,” Raine said in an interview. But he says the bees exposed to neonicotinoids grew worse over time.
“They don’t improve, they actually get less efficient,” said Raine, who is calling on regulators to consider the “knock-on” impacts of the pesticides on bumblebees which like honey bees are essential pollinators.
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.
Health Canada, which regulates the use of neonicotinoids, did not respond to a request for comment on the new studies before deadline. Erin O’Hara, communications officer with CropLife Canada that represents the companies that market neonicotinoids, said the industry has not yet had a chance to review the new research.
© COPYRIGHT – POSTMEDIA NEWS