Agricultural Pesticides Threaten Surface Waters Globally, Study Finds

Pesticides have led to a 30 percent reduction of aquatic biodiversity, say researchers
April 16, 2015 Updated: April 15, 2015

A first-of-its-kind German study that examined the global use and impact of pesticides has found that in over half of 2,500 sites tracked in 73 countries including Canada, chemical concentrations exceed recommended levels.

The researchers describe the results as alarming and warn that aquatic life is being hurt, with the problem in the future possibly rivaling climate change as a global environmental issue.

“What they found was just over half of the sites that they considered had exceeded these regulatory thresholds. That means there is reason to think that the aquatic life has been affected in half of these cases,” said Jules Blais, director of Laboratory for the Analysis of Natural and Synthetic Environmental Toxicants at the University of Ottawa.

Blais edited the study, titled “Agriculture Insecticides Threaten Surface Waters at the Global Scale,” which appeared in the US Proceedings of the National Academy of Sciences earlier this week.

I think this is a real eye-opener in light of the global impacts that agriculture is having on aquatic life and the natural world.
— Jules Blais, University of Ottawa

Authors Sebastian Stehle and Ralf Schulz from the Institute for Environmental Science in Germany reviewed 838 studies using a meta-analysis to gauge insecticide levels in surface water. Their analysis found that 11,300 insecticide concentrations present in half of the 2,500 water sample sites spread across the globe exceeded regulatory limits in the European Union and the United States.

“I think this is a real eye-opener in light of the global impacts that agriculture is having on aquatic life and the natural world,” said Blais. “It illustrates the human footprint I think a little more clearly than what we were aware of before.”

The researchers warn that aquatic organisms such as insects and crustaceans are being impacted by the pesticides, estimating that a 30 percent reduction in aquatic life has occurred as a result of the pesticide levels. The category does not include fish, although fish populations that rely on these organisms would be impacted.

“Surface water pollution resulting from current agricultural insecticide use constitutes an excessive threat to aquatic biodiversity,” the authors write.

“Our analysis suggests that fundamental revisions of current regulatory procedures and pesticide application practices are needed to reverse the global environmental impacts of agrochemical-based high-intensity agriculture.”

Potential reasons insecticides are finding their way into surface waters include the failure of risk-assessment procedures currently in place or farmers’ non-adherence to pesticide application directions, the authors said.

“This gives us a sense of the global state of things regarding the global distribution of pesticides and their impact on aquatic life,” said Blais. “It is a wakeup call and it shows the levels at which these pesticides are being used.”

The researchers note that although insecticides can dissipate quickly in water, they may kill aquatic organisms during an initial high-concentration period due to their high toxicity.

“Taken together, our results seriously challenge the protectiveness of the current regulatory insecticide risk assessments and management procedures at the global scale,” the authors conclude.

“To date, agriculture occupies 40 percent of the world’s land surface and agricultural production is forecast to undergo substantial intensification. This situation leads to the projection that future agricultural activities may rival climate change in their environmental impacts.”

The researchers acknowledged that they could only retrieve data for 10 percent of global agricultural surface water, with data missing for Russia, large parts of Africa, and northwestern South America.

Kaven Baker-Voakes is a freelance reporter based in Ottawa.