Northumberland: A look at the science on neonics

In the ECO’s latest Annual Report, we examined the environmental effects of neonicotinoids – a class of pesticides used throughout Ontario. New research on neonicotinoids is being published at an astounding rate, demonstrating an overwhelming level of concern within the scientific community. While much of this research initially focused on the effects of neonicotinoids on pollinators, serious issues are being raised surrounding the broader ecological implications of neonicotinoid use.

The use of neonicotinoids has increased significantly since their introduction in the 1990s. They are now the most widely used insecticides in the world. Neonicotinoids act systemically, meaning that they diffuse throughout the tissues and sap of treated plants, and are found in pollen, nectar and guttation droplets (i.e., small drops of liquid exuded by some plants). They are most commonly used as seed treatments, but they can be applied in other ways, such as foliar sprays and soil additions. Pollinators are primarily exposed to neonicotinoids through nectar and pollen and, notably, through contaminated dust generated during the planting of treated seeds.

Exposure to neonicotinoids has been linked to both lethal and sublethal effects on pollinators. There is now clear evidence that acute exposure to neonicotinoid-contaminated dust is linked to mass bee deaths observed during the planting of seed treated crops. In fact, Canada’s Pest Management Regulatory Agency (PMRA)’s investigation into the 2012 and 2013 bee kills in Canada concluded that neonicotinoids were a contributing factor in many cases. Accordingly, in 2013, the PMRA declared that “current agricultural practices related to the use of neonicotinoid treated corn and soybean seed are not sustainable.” (.pdf)

Furthermore, a number of studies have concluded that neonicotinoids can also cause adverse sublethal effects on bees, such as:

Even with lower concentrations, cumulative and/or synergistic effects may cause impaired colony function or even failure. For example, one recent study concluded that chronic sublethal stress can be a cause of honey bee colony failure, noting that if many bees in a colony become impaired, it may lead to a cumulative effect on normal colony function.

In recent years, substantial declines in honey bee populations have been observed, notably in North America and Europe. This decline includes colony losses in Ontario: over the last eight years, the average overwintering loss of bee colonies in Ontario has been approximately 34 per cent – more than double the 15 per cent winter loss rate that is considered to be acceptable by apiculturists. In fact, last winter, Ontario lost 58 per cent of its honey bee colonies. In addition to these overwintering losses, a number of other large-scale bee deaths have been reported in Canada. In the spring and summer of 2012 and 2013, the PMRA received numerous reports of honey bee mortalities (.pdf) from beekeepers in Ontario, Quebec and Manitoba. The resulting Health Canada report concluded that the planting of corn seeds treated with neonicotinoids contributed to the majority of the bee mortalities that occurred in the corn growing regions of Ontario and Quebec.

Signs are emerging that many wild pollinators, particularly bumble bees, are in decline as well. For example, the Committee on the Status of Pollinators in North America has stated that long-term population trends are demonstrably downward for several wild bee species, as well as for some butterflies, bats and hummingbirds.

Although the impact of neonicotinoids on bees has received a great deal of attention, honey bee declines may be a visible warning sign of a larger ecological problem.  Troubling questions are being raised about the broader environmental effects. Only a small portion of the active substance is taken up (.pdf) by plants in seed-treated crops, while the rest enters the environment. This is of great concern because neonicotinoids are not only persistent in soil and water, but are also water soluble and highly mobile within ecosystems.

As a result, neonicotinoids can accumulate in soil, potentially having adverse effects on soil ecosystems (.pdf) and creating a likelihood of uptake by subsequently planted crops and wild plants. They also have the potential to migrate into ground and surface water. Runoff and spray drift can impact aquatic invertebrates in streams and ponds. For example, in one study conducted in California, imidacloprid was detected in 89 per cent  of surface water samples – with 19 per cent of samples exceeding toxicity guidelines. Another recent study in the Netherlands demonstrated that aquatic macro-invertebrates are less abundant in surface water with higher imidacloprid concentrations, suggesting potential consequences for the food chain and ecosystem functions.

Neonicotinoids may also be posing serious risks to birds and mammals. For example, a July 2014 study found that declines in insectivorous birds are associated with high neonicotinoid concentrations. The researchers state that their “results suggest that the impact of neonicotinoids on the natural environment is even more substantial than has recently been reported and is reminiscent of the effects of persistent insecticides in the past.” Questions are also being raised regarding the potential human health effects of neonicotinoids.

In June 2014, the Task Force on Systemic Pesticides released the most comprehensive review of the effects of neonicotinoids to date. The Worldwide Integrated Assessment of the Impact of Systemic Pesticides on Biodiversity and Ecosystems examined over 800 scientific studies spanning the last five years, including studies sponsored by industry. Among the study’s main conclusions is that “The combination of prophylactic use, persistence, mobility, systemic properties and chronic toxicity is predicted to result in substantial impacts on biodiversity and ecosystem functioning.”

As a result of this rapidly evolving body of research, the ECO recommended that the Ministry of Agriculture and Food and the Ministry of the Environment undertake monitoring to determine the prevalence and effects of neonicotinoids in soil, waterways and wild plants. The Ontario government needs to develop an effective action plan on neonicotinoids. We cannot ignore the problem and accept the risk of an ecological catastrophe.

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