The Environmental Repercussions of Pesticides on Food

Bioaccumulation of pesticides on food can lead to a much higher concentration of toxins in the environment than is originally intended, with disastrous consequences.


| January 2015



American robin

Birds like this robin and other predators often pay the price for relatively low-concentration application of pesticides on food crops, as the toxins bioaccumulate in prey animals and ultimately reach the upper levels of the food chain.

Photo by Fotolia/Andrea Izzotti

The result of a rigorous two-year investigation that took award-winning journalist and filmmaker Marie-Monique Robin across North America, Europe and Asia, Our Daily Poison is a shocking account of the dangerous chemical compounds that have infiltrated our food chain. Robin documents the many ways in which we encounter chemicals in our everyday lives—from the pesticides that blanket our crops to the additives and plastics that contaminate our food—and their effects over time. The following excerpt is from chapter 3, “Elixirs of Death.”

The Silence of the Birds

An expert ornithologist ever since her long walks on the banks of the river of her childhood, Rachel Carson had thought of titling her book The Silence of the Birds, because the fate of those innocent creatures seemed to her emblematic of the process of destruction at work. In her research she had consulted hundreds of letters to government agencies and universities, such as a letter from a housewife of Hinsdale, Illinois, found in the archives of Robert Cushman Murphy, a renowned ornithologist at the American Museum of Natural History: “When we moved here six years ago, there was a wealth of bird life,” she wrote. “After several years of DDT spray, the town is almost devoid of robins and starlings; chickadees have not been on my shelf for two years, and this year the cardinals are gone too; the nesting population in the neighborhood seems to consist of one dove pair and perhaps one catbird family. It is hard to explain to the children that the birds have been killed off, when they have learned in school that a Federal law protects the birds from killing or capture.”

These individual observations—chemical industry skeptics called them “anecdotal”—were confirmed all through the 1950s in reports from such official organizations as the U.S. Fish and Wildlife Service (which employed Carson). It noted the striking phenomenon of “blank spots weirdly empty of virtually all bird life.” The same thing occurred in Europe, as shown by “the deluge of reports of dead birds [that] reached…the Royal Society for the Protection of Birds”; the cause was the treatment of seeds with fungicides and insecticides before planting, which indirectly led to the death of 1,300 foxes between November 1959 and April 1960. The foxes died because they ate the poisoned birds, who had filled up on earthworms, themselves stuffed with the poison covering the seeds.

To fully understand the twofold phenomenon of bioaccumulation and bioconcentration—I repeat this because it is of the greatest importance—it is necessary to refer to the long study conducted by Professor George Wallace, an ornithologist at the University of Michigan, following DDT spraying of the campus and the surrounding area in 1954. The purpose of the “program” was to exterminate the bark beetles thought to be the carriers of Dutch elm disease. The following spring everything seemed normal: robins returned to the leafy campus to build their nests. Then suddenly, the campus turned into a “graveyard.” According to Wallace, “ ‘in spite of the assurances of the insecticide people that their sprays were “harmless to birds,” the robins were really dying of insecticidal poisoning; they exhibited the well-known symptoms of loss of balance, followed by tremors, convulsions, and death.’ ”

Perplexed, the ornithologist contacted Dr. Roy Barker, a member of an Illinois research center, whose work had “traced the intricate cycle of events by which the robins’ fate is linked to the elm trees by way of the earthworms.” DDT forms a “tenacious film” over leaves and bark, killing, along with the targeted bark beetles, beneficial insects, predators invaluable for ecological balance and plant protection. In the autumn the worms swallow the insecticide deposited on the dead leaves and in the earth through poisoned insects, and accumulate it in their fatty tissue without being directly affected. Pesticides are like Russian roulette: their effects vary from species to species and in this case earthworms are not sensitive to DDT (by contrast, however, Monsanto’s Roundup is fatal to them). The following spring, the heedless robins sign their death warrant by eating the earthworms. According to Barker, a fatal dose takes only eleven worms.

But that was not the end of the story. In the years after the campus spraying, Wallace observed that the robins that had survived had lost the ability to produce offspring. The numbers are eloquent: in 1953 the adult bird population was 370; five years later it had fallen to “two or three dozen.” This drastic population reduction was coupled with a disturbing phenomenon: Wallace had “ ‘records of robins and other birds building nests but laying no eggs, and others laying eggs and incubating them but not hatching them. We have one record of a robin that sat on its eggs faithfully for 21 days and they did not hatch.’ ”