The killing fields

The_killing_fields

Ground-breaking research reveals that a class of agricultural pesticides is the likely culprit in the deaths of hundreds of millions of birds. Worse still: Canada continues to market neurotoxic chemicals with the full knowledge of their impact

by Paul Webster

 

The cormorant’s brilliant green eye is flecked with yellow pinpoints, and just above the pupil, a shimmer of cerulean blue reflects the early summer sky over Hamilton Harbour. Braced in the crook of Shane de Solla’s arm, the large black waterbird seems calm. But de Solla, a wildlife biologist with Environment Canada, has studied big birds long enough to know better than to relax his hold, especially not when taking a blood sample. To do so, de Solla has to push back the downy black feathers under the cormorant’s wing to reveal a tiny patch of pink skin. Once a few millimetres of blood have been extracted using a syringe, Jim Quinn, a McMaster University molecular ecologist collaborating with de Solla’s research team, says the bird looks thirsty. “Some Gatorade might be in order,” he suggests.

Bad chemistry

When the U.S. Environmental Protection Agency (EPA) banned the pesticide Carbofuran in May, lovers of migratory birds cheered. Carbofuran is in a class of pesticides that act as neurotoxins, inhibiting brain activity. The chemical has been widely used in North America since the 1970s on crops such as corn, barley, onions, peppers, raspberries and strawberries.

Studies have long suggested Carbofuran is linked with the devastation of bird populations in North America, which have caused wildlife researchers to call for bans. Now that the United States has done so, Health Canada seems poised to follow.

The word “bird,” however, does not appear in the 104 pages of tightly reasoned scientific justification the EPA provided for the ban (see www.epa.gov/oppsrrd1/reregistration/carbofuran/carbofuran_noic.htm). The main reason cited is that the levels of Carbofuran in drinking water and food represent a risk to infants and children.

Paul Webster

Quinn and de Solla are spending several months here this year and next as part of a study probing the impact of airborne toxins on cormorants. The work is painstaking, but wildlife researchers across Ontario say such field research is increasingly urgent. In recent decades, populations of migratory birds have declined dramatically around the province, which traditionally hosts billions of birds during the summer months. Three songbird species were added to Canada’s list of species at risk last year alone, notes Bridget Stutchbury, a York University biologist specializing in birds that migrate between Central America and North America. And although lab studies have shown elevated exposure to pollutants such as pesticides, solvents and flame retardants to be lethal, their real-world impact remains poorly understood. Recently, attention has focused in particular on a class of pesticides that some scientists are fingering as likely culprits in the deaths of hundreds of millions of birds.

Perhaps the most vigorous voice in this group is that of Pierre Mineau, the Canadian government’s top expert on pesticides and birds. Through research going back to 1978, he has helped prove that many pesticides used in the past were wreaking ecological havoc on wildlife – especially on large migratory species that consumed smaller prey contaminated with the chemicals. But, as regulators in Canada, the United States and Europe stepped in to ban compounds such as DDT, Mirex and Chlordane, chemical companies introduced a new generation of products.

These pesticides, with names such as Carbofuran, Fonofos, Diazinon and 2-4D, are based on smaller chemical components that degrade faster in the environment. Governments anxious to phase out DDT and its more persistent brethren approved these pesticides for sale, says Mineau, who spent 1982 to 1996 reviewing the new chemical formulations for Environment Canada. The great majority of safety studies limited their focus to how laboratory rats reacted to eating the chemical pellets. “Unfortunately, they were required to do only limited testing on birds,” says Mineau. Since then, research by Mineau and others has shown that these new compounds are acutely harmful to birds and other wildlife. Birds appear to be “exquisitely sensitive” to the pesticides, which scramble their nervous systems. And yet, he says, “we went on marketing and developing these neurotoxic chemicals with the foreknowledge they were very toxic to birds.”

Reviewing pesticide applications in Environment Canada laboratories in Ottawa, Mineau grew increasingly worried about the lack of data on the new chemicals’ effects on wildlife in the fields and forests sprayed with them. So, in the early 1990s, he decided to head back into the field. In a dazzlingly prolific series of studies – he has produced about 100 publications since 1990 – he went on to report disturbing findings about these chemicals and their effects on birds, as well as insects.

In the case of the pesticide Carbofuran, made by Philadelphia-based FMC Corporation and used on crops ranging from potatoes to canola, Mineau estimated that, at the peak of its use in the 1980s, the chemical killed as many as 90 million birds, comprising some 45 species, every year in the United States alone. In the same decade, Mineau estimated, the chemical caused between 244,000 and 1.3 million songbird deaths in western Ontario per year. Carbofuran (along with the insecticides Fonofos and Terbufos) was also implicated in a large number of bird deaths in British Columbia’s Fraser Delta in the 1980s and 1990s.

Researchers not only saw evidence of birds dying after ingesting pellets of the chemicals, they also uncovered more subtle effects, seemingly the result of mere contact with sprayed pesticides. Neurological changes appeared to be reducing the ability of birds to feed themselves and their young, eventually resulting in death. In a 2000 study in southern Ontario led by one of Jim Quinn’s PhD students, Christine Bishop, where Mineau sat on the academic committee, it was found that tree swallows in apple orchards were starving, because the chemicals both exterminated the insects that the birds feed on and depressed the birds’ brain activity, diminishing their ability to hunt. The study linked pesticides to a drop in the number of eastern bluebird and tree swallow nestlings that survived to maturity and found thyroid, endocrine and immune system damage in young birds exposed to pesticides in the orchards.

The focus on apple orchards was deliberate. According to Mineau, of all the agricultural lands in the province, the 12,000 hectares devoted to growing fruit are treated with the greatest number of types and applications of pesticides – including such new-generation insecticides as Azinphos- methyl, Diazinon, Phosalone and Phosmet. As the 2000 study revealed, individual nests of bluebirds and tree swallows, which commonly breed and forage in apple orchards, were exposed to as many as seven pesticide applications and up to five pesticide mixtures. By focusing on these two species in orchards, Bishop was able to establish that pesticide use depressed mature birds’ brain activity by about 40 percent. Nestlings’ brains were even harder hit. The scientists found that the chemicals did not kill the birds directly. Instead, they were losing the ability to find food and raise their young.

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