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Rachel Carson didn't hate pesticides — she maintained that they were essential if used wisely. But she hated the word "pesticides."

This was partly because she thought that calling any species a "pest" was arbitrary. But mainly it was because she believed that the idea that a chemical poison can discriminate between "bad" organisms and "good" ones was a lie. Carson devoted herself to destroying this illusion in her landmark book "Silent Spring," the 1962 polemic against the heedless use of synthetic pesticides such as DDT and its several toxic cousins.

"Silent Spring" turned 50 last fall, still revered as one of the pillars of the modern environmental movement, and, in light of recent developments, perhaps regarded with more than a small measure of déjà vu.

Out in the fields where our food is tended, "Silent Spring" is looking as relevant as ever.

Since 2005, scientists have struggled to explain an alarming decline of honeybees, which are essential to crop production. Various causes are on the table, including viruses, fungal infections, habitat loss and, of course, pesticides.

Pesticides, particularly a popular insect-killing class of poisons called neonicotinoids, have been suspected of contributing to "bee colony collapse disorder" ever since the problem came to light in 2005. Neonicotinoids are systemic poisons that are applied to seeds and then become incorporated in the tissues of the adult plant. They're meant to kill aphids and other crop-destroying insects.

Earlier this year, researchers at the University of Dundee in Scotland and at Newcastle University in England discovered that neonicotinoids and another widely used insecticide called coumaphos — both are nerve poisons — disrupt neural activity in the brains of ­honeybees, affecting their behavior and impairing their ability to forage and pollinate. These effects were seen at the small, sublethal doses the bees could encounter in the wild or that might accumulate in their hives. The studies also showed that the toxic effects were magnified when the bees were exposed to both pesticides at the same time.

All of this new evidence mirrors the story Rachel Carson first told a half-century ago. It was a story based on the steadily accumulating evidence that pesticides usually turned out to be toxic to many if not most nontargeted organisms. Better, Carson said, to think of these chemicals as "biocides."

Lest anyone miss the point, she convincingly compared pesticide use to the then-ongoing contamination of the Earth with fallout from nuclear-weapons tests.

Paul Müller, the Swiss chemist who demonstrated the insect-killing properties of DDT in 1939, won a Nobel Prize for his discovery. People thought DDT would alter the course of history by ending diseases such as malaria and typhus, and by bringing about revolutions in agriculture and forestry. But as early as 1945, Carson — who worked for the U.S. Fish and Wildlife Service — learned that government experiments with DDT showed it was toxic to every species tested. DDT was known to persist in the environment, and as the tests continued the researchers found that it was devastating to wildlife, and that it was amplified and stored in the tissues of virtually every organism in the food chain.

Even so, through the 1950s and into the 1960s, DDT and other pesticides came into ever-greater use. DDT was dropped from airplanes, was sprayed into trees and buildings, and was routinely dispersed in neighborhoods by fogging trucks as children frolicked in the murk. It was incorporated into paints and fabrics and shelf papers. DDT was everywhere. And that, Rachel Carson insisted, was the main problem. Contaminate one corner of the environment, and you risk contaminating the whole thing.

"Can anyone believe it is possible," Carson wrote in "Silent Spring," "to lay down such a barrage of poisons on the surface of the earth without making it unfit for all life?"

Fifty years ago, those poisons fell from the sky and rode the winds and took up residence in living things. Now we hide them within what Carson called the Earth's "green mantle." It's a seductive concept, the belief that we can make our food sources poisonous to pests, yet do no other harm. Historically, this kind of optimism has been unwarranted. The "control of nature" as it was called back in Carson's time described an attractive idea that has often led to an unhappy outcome.

One part of the story that has not changed in the decades since "Silent Spring" is the tendency to choose up sides and get to the bottom of things later. In a move that deepened the suspected connection between neonicotinoids and bee declines, the European Union this spring banned the use of neonicotinoids on crops attractive to bees — over the strenuous objections by Great Britain and seven other countries. The companies that make these pesticides maintain that they are safe, while also saying they favor continuing research — though it should be noted that calling for more research is a well-established industry strategy for keeping suspect chemicals on the market.

And while it's always a good idea not to get ahead of the data — there is not yet compelling proof for any cause or causes of bee losses, pesticides included — we remain confronted by the original problem, which only seems to be getting worse.

About one-quarter of the American food supply requires pollination by bees. Last year, American beekeepers reported losses approaching 50 percent of their hives. Those hives that survive are increasingly stressed as they are trucked from crop to crop. A coalition of environmentalists and beekeepers is suing the Environmental Protection Agency to end the use of two popular neonicotinoids. Meanwhile, just last month, Canadian researchers reported that steep declines in populations of grassland birds are correlated with exposure to insecticides that may well include neonicotinoids.

So the problem is an urgent one. We cannot give up the attempt to control pests — to, as Rachel Carson put it, "tilt the balance of nature in our favor." She added an important caveat: "But when we make the attempt we must know what we're doing. We must know the consequences."

We're not sure of what we're doing with these newer pesticides, or whether the disaster we're seeing with bees is one of the consequences.

The only thing we know for sure is that if using these chemicals is a mistake, it's one we've made before.


William Souder, of Stillwater, is the author of "On a Farther Shore: The Life and Legacy of Rachel Carson," which was published last fall on the 50th anniversary of "Silent Spring."