The insect world’s most successful hunters show how the toxic metal moves through our environment—and how we can reduce our exposure.
Dragonflies, those colorful bugs zooming around like mini-helicopters, are more than just a spectacular sight. These iridescent predators may also be the best way to detect where and how mercury—a toxic metal for both people and wildlife—is accumulating in our environment, a new study says.
Scientists have often used fish or birds as harbingers of mercury contamination. But dragonflies are an even better indicator. For one, their larvae develop in almost any type of water body, including tiny desert potholes or muddy marshes that can’t support larger animals. Plus, it’s cheaper, easier, and more accurate to analyze mercury in insect larvae than it is in fish or birds.
The World Health Organization lists mercury as one of the top 10 chemicals of major public health concern, and the metal exists in our atmosphere at a concentration of about 450 percent higher than natural levels due to humans’ industrial activities, including coal burning and cement production.
Since 2009, more than 7,000 citizens and researchers have collected dragonfly larvae from 150 U.S. national parks as part of the Dragonfly Mercury Project, which is run by the U.S. Geological Survey and the National Park Service. This community science effort, now the nation’s largest assessment of mercury contamination, has analyzed tens of thousands of dragonfly larvae.
In doing so, scientists have discovered surprising patterns in how mercury moves through the landscape, including where concentrations of this harmful metal are the highest.
This successful research effort shows dragonfly larvae should be the gold standard for detecting mercury, says Collin Eagles-Smith, a USGS research ecologist and science lead for the Dragonfly Mercury Project who co-authored a study on the topic recently in the journal Environmental Science and Technology.
“There are no safe levels of mercury,” says Alexandra Scranton, director of science and research at Women’s Voices for the Earth, a nonprofit working to reduce and eliminate toxic chemicals. “Yet we all have it in our bodies. We have unfortunately contaminated our entire world.”
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