The Same Pesticides Linked to Bee Declines Might Also Threaten Birds

Neonicotinoids are washing off of their host seeds and into water bodies—threatening not just aquatic insects but the birds that rely on them.

On a late spring morning, Christy Morrissey, a wildlife ecotoxicologist at the University of Saskatchewan, drove her mud-splattered pickup past an undulating sea of cultivated fields two hours north of Saskatoon. Now and then, the land rose to form low green hills, and the sound of aspen leaves rattling in tall-grass sloughs floated in the open windows. All the way to the horizon, shallow ponds, called potholes, punctured the landscape, each dotted with ducks and ringed with bulrushes and cattails.

After inspecting a map drawn by a student, Morrissey pulled to the side of the gravel road, grabbed a small cotton bag, and crept stealthily toward a wooden box nailed to a fence post. Like a pouncing cat, she clapped her bag over its round entrance hole, and then cautiously opened the box’s side door. Staring into the middle distance, she felt around inside. “Got her,” she said, extracting a glossy Tree Swallow and gently tipping her head-first into the bag. “Fifty percent of the time I can catch the female on her eggs.”

Back in her truck, Morrissey read the tiny silver band on the swallow’s leg, then carefully weighed and measured it. The data, together with that of nearly 500 birds, would help her compare the health of swallows that live near industrial-scale farms with those that live in grassland areas. Over the next couple of weeks, she’d also collect blood and feather samples from 12-day-old chicks to assess their stress levels and the quality and composition of their diet.

A century ago, the fields over which these birds swoop and dive were part of the largest grassland on Earth, stretching 276,000 square miles from Iowa to Alberta. Now oil seed and cereals cover much of southern Saskatchewan. The prairie potholes still host nearly 200 species of ducks, songbirds, and shorebirds, but more than half of these species are in steep decline, and only 30 percent of the region’s original wetlands remain.

“All of this is canola,” Morrissey said, gesturing in three directions as she drove to the next nest box. “And all of it is treated with neonicotinoids.” Neonics, as they’re known, are pesticides chemically related to nicotine that act as powerful insect neurotoxins. Although aimed at pests, neonics have been shown to affect pollinators, too; they’ve been linked to colony collapse disorder, which devastated 44 percent of American beekeepers’ hives between 2015 and 2016. Now, after five years of intense investigation, Morrissey suspects that neonics may affect a far broader and more complicated food web—one that starts at the bottom of ponds, entangles aquatic insects, and ensnares their ultimate consumers: grassland birds.

Typically deployed as brightly colored seed coatings, neonics may seem more innocuous than the pesticides they were designed to replace two decades ago. They are certainly easier to work with: Farmers simply sow the seeds, then sit back as the pesticide is incorporated over time into the plant’s roots, stems, leaves, and pollen. Pests munch on any of these parts, their nervous system goes haywire, and they keel over, dead. Because plants express neonics through all growth stages, farmers can eliminate one or more trips over their fields with a pesticide-filled sprayer, saving fuel and reducing the volume of chemicals applied.

Even as the amount of all pesticides applied to North American farmland has dropped in recent years, from 955 million pounds in 1997 to 789 million pounds in 2012 (the latest available data), the use of neonics has continued to grow. Considered cheap insurance for expensive seeds, they are now the most widely adopted pesticide in the world, with an expected 2018 market value of $4.2 billion. Neonic-treated corn, soy, and cotton cover 150 million acres of the United States, about a twelfth of the area of the lower 48. In Canada, neonics are used on 44 percent of cropland, including some 21 million acres of canola, the nation’s second-most-cultivated crop.

But their delivery system has a major flaw. “Only about 5 percent of the compound is taken up by the plant,” Morrissey says. The rest leaches off the seed, accumulates in soil, and sluices via snowmelt, rain, and groundwater seepage into ponds and wetlands, where insects like midges and caddis flies—a staple for billions of grassland birds—start their lives.

A 2015 study by the U.S. Geological Survey found neonics in 63 percent of water samples taken from 48 streams. In Canada, researchers detected at least one neonic—there are seven types on the market—in 91 percent of wetlands. Unlike many liquid pesticides, neonics can persist and accumulate in ponds for months, if not years. In other words, says the Center for Food Safety, a nonprofit that promotes sustainable agriculture, neonics are “almost tailor-made to contaminate the environment.”

Christy Morrissey grew up in Vancouver, dreaming of becoming a vet: She loved animals, and she felt at peace in nature. At the University of British Columbia, she took classes in zoology and ecology, but she also entertained thoughts of becoming an English teacher. “There was no culture of science among my family or friends,” she says, “and I had no female scientist role model at the university.” Then one day the renowned ornithologist Jamie Smith invited her on a field trip in the Okanagan Valley. Soon, she was spending lunches and weekends birding and evenings learning bird calls. “My mom thought I was nuts,” she says.

After graduating with a degree in zoology, Morrissey volunteered for the Canadian Wildlife Service to study raptors and carbamates, a class of pesticide now banned in Canada and the European Union. A pattern of sleuthing formed: For her doctorate at Simon Fraser University, Morrissey investigated how atmospheric pollutants got into mountain-stream food webs, then rippled up to American Dippers; as a postdoc, she tracked how arsenic—a treatment for pine-beetle infestations—affects woodpeckers and Osprey and how acid rain affects European Dippers.

In 2010, Morrissey accepted an assistant professor position at the University of Saskatchewan. Among the first people she called for advice on developing a research program was Pierre Mineau, then a senior research scientist with Environment Canada and an expert on the ecotoxicology of pesticides. “Study neonicotinoids,” he told her, without hesitation. Morrissey hadn’t ever heard the word. But she quickly learned that neonics are ubiquitous; that many dealers don’t sell seeds without them; and that crops, in many cases, don’t even suffer from the specific pests the chemicals target. “I knew that treating every seed in the ground, whether you need that crop protection or not, was a bad idea,” she says.

So with a small army of students, Morrissey designed a Hydra-like research program that is exploring, piece by piece, how neonics move from farm fields to waterways, how they affect the invertebrates that live there, and how these aquatic insects—their abundance, diversity, and health—in turn affect birds.

Late spring is a busy time for Canadian field biologists, and the morning after Morrissey’s survey of nest boxes, she joined one of her graduate students, Erin Maloney, in the grassy meadows of the St. Denis National Wildlife Area. As the pair topped a gentle rise, they gazed down upon the centerpiece of Maloney’s investigations: a small village of yellow-and-white teepees emerging from a cattail-ringed pond. The 21 limnocorrals, as they’re called, are helping Maloney figure out what effect neonicotinoids have on aquatic bugs.

The women climbed into an aluminum canoe and paddled out to the middle of the pothole, where a wide plastic sleeve stretched from the pond’s mucky bottom to a meter-square frame floating on its surface. Above the frame, netting rose to form a narrow funnel that dead-ended with a jar of ethanol. Different mixtures of neonics swirled inside each corral, along with pond-dwelling insects such as midges, damselflies, and mosquitoes. If they survived their aquatic phase, the insects would fly up and die in the jar. Maloney planned to compare how many adults emerged from corrals dosed with neonics to those in controls; she would also determine whether pesticide exposure shifted the population’s composition.

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In dozens of other studies that Morrissey analyzed for a journal article in 2014, scientists have found that neonics can affect abundance and survival of aquatic insects—even at levels below current U.S. water-quality guidelines. Still, those in the industry aren’t convinced. “I don’t think Morrissey has demonstrated that residues actually in the water from field applications are resulting in significant loss of aquatic invertebrates,” says Ray McAllister, senior director of regulatory policy at CropLife America, which represents pesticide manufacturers. “The levels are well below those of concern established by EPA.”

Morrissey and other researchers believe EPA guidelines—which are 30 times higher than those established throughout Europe and Canada—are out of date and too high. One reason: Neonic makers tested the compounds on Daphnia, a tiny freshwater crustacean commonly used as a model for ecotoxicological studies. But Morrissey has found that Daphnia is uniquely insensitive to neonics, while midges—the most common insect in prairie potholes—are especially vulnerable. Moreover, industry usually tests only for acute exposures to single substances, but aquatic invertebrates are continuously exposed to sub-acute levels of multiple compounds over long periods of time. Researchers have also discovered that while some insects survive neonics, their offspring may not pupate—an epic reproductive fail.