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Are neonicotinoid pesticides contaminating wetlands?

Researchers suspect a class of pesticides is responsible for insect and bird declines

  • Mar 31, 2014
  • 390 words
  • 2 minutes
Wetlands in Saskatchewan Expand Image

University of Saskatchewan researchers are worried pesticides used in the province are connected to the decrease in bird and bug populations.

The pesticides, called neonicotinoids or neonics for short, are commonly applied to seed before they’re planted. Neonics paralyze invertebrate bugs by binding to receptors in their central nervous system.

University of Saskatchewan assistant professor and biologist Christy Morrissey believes these pesticides have seeped from farm fields to surrounding wetlands and are affecting the biodiversity of insects and birds in those areas.

“Last spring, we were detecting neonics in over 90 per cent of wetlands, and that was before seeding,” Morrisey says. “This means these chemicals are in the water for a long time.”

Morrissey’s team estimates that 225,000 kilograms of the pesticides were applied to seeds planted in over 11 million hectares. “It’s a huge area that’s being blanketed,” she says. “These chemicals are being applied to every square inch of landscape.”

Unlike other popular pesticides of the past, neonics are extremely water soluble. Wetlands have lots of sediment and algae, making chemical breakdown more difficult than in soil, which is exposed to light. As well, a long, cold winter and lack of precipitation are perfect conditions for retaining the pesticides.

From there, insects like mosquitoes and midges are potentially exposed to these chemicals throughout their life cycle. Though neonics exposure levels are fairly low, Morrissey says they are constant.

“These organisms are continually exposed to pesticides and concentrations go up after seeding,” she says.

While these particular pesticides may be harmful, Christopher Cutler, an associate professor in the Department of Environmental Sciences at Dalhousie University, says this class of pesticides is less harmful than older organophosphate pesticides, which were fatal to people. Humans have receptors that aren’t sensitive to compounds in neonics, whereas insects, especially bees, are the opposite.

“We’ve known about bee declines for decades and people think this is a new problem,” Cutler says. “I fear this prophylactic approach of automatically planting seeds with pesticides is something that needs to be addressed.”

Cutler says neonics could be used more carefully.

“To suggest neonics are the cause is not looking at what else is happening. I’m not saying neonics are used in the best possible way. I’m not a fan of pesticides, but I understand their role and, compared to the alternative, neonics are much better.”


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