Exposure to a cocktail of agrochemicals significantly increases bee mortality, but regulators may be underestimating the dangers of pesticides in combination.
Bees pollinate 71 types of plants that provide 90 percent of the world's food, according to the United Nations. The steep drops in insect populations worldwide in the recent years have prompted fears of dire consequences for food security and natural ecosystems.
A research reviewed dozens of published studies over the last 20 years that looked at the interaction between agrochemicals, parasites and malnutrition on bee behaviors -- such as foraging, memory, colony reproduction -- and health. It found that pesticide interaction with other chemicals was likely to be synergistic, meaning that their combined impact was greater than the sum of their individual effects.
These "interactions between multiple agrochemicals significantly increase bee mortality," said co-author Harry Siviter, of the University of Texas at Austin.
"Regulators should consider the interactions between agrochemicals and other environmental stressors before approving their usage," he told AFP.
"The results demonstrate that the regulatory process in its current form does not protect bees from the unwanted consequences of complex agrochemical exposure," he added.
"A failure to address this will result in the continued decline in bees and their pollination services, to the detriment of human and ecosystem health," the researchers concluded.
In a commentary also published in Nature, Adam Vanbergen of France's National Research Institute for Agriculture, Food and Environment said that pollinating insects face threats from intensive agriculture, including chemicals like fungicides and pesticides, as well as a reduction of pollen and nectar from wild flowers.
"This study confirms that the cocktail of agrochemicals that bees encounter in an intensively farmed environment can create a risk to bee populations," Vanbergen wrote.
He said there had been a general focus on impacts on honey bees, but added there is a need for more research on other pollinators, which might react differently to these stressors.
