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Exaggerated Importance. While many insecticides are roughly as harmless as DDT, others are considerably more poisonous to humans. But in the opinion of respected experts of the U.S. Public Health Service, none have done appreciable damage to the U.S. public or are likely to do so. In heavily sprayed cotton-growing areas of the Mississippi Delta, says Assistant Surgeon General Dr. D. E. Price, health is as good as in sparingly sprayed neighboring areas. The same-report comes from California, where insecticides are heavily sprayed on orchards and fields. Says Robert Z. Rollins, chief of the division of chemistry of the California department of agriculture: "Pesticides used properly present no threat to people, no matter how widespread their use becomes."
Humans generally protect their domestic animals from any ill effects; wildlife does not fare as well. Wild animals, birds, fish, and friendly insects are among the valued inhabitants of the U.S., and a good part of Miss Carson's book tells about the deadly effect of wholesale spraying on these pleasant and harmless creatures. In vivid language, she tells how DDT spraying to protect elm trees from Dutch elm disease nearly wiped out the bird populations of many Midwestern cities, how fruitless attempts to exterminate the imported fire ant of the South by airplane dusting with dieldrin had dire effects on many kinds of wildlife.
Even scientist defenders of pesticides admit that these things have happened, but they maintain that their importance is exaggerated. According to the Entomological Society of America, only 0.28% of the 640 million acres of U.S. forest land is treated annually, and 613 million acres have never been treated. Insecticides are used mostly on crop lands, which have little wildlife, and on human residential areas to protect shade trees— the use that causes the most conspicuous damage to wildlife.
One result is the wholesale death of robins, which form a large part of suburban bird populations. The robins live on earthworms (that is why they are plentiful in the suburbs, where worm-bearing lawns abound), which concentrate insecticides without being damaged themselves. When the robins eat these insecticide-full worms, they die. The slaughter may continue for several years, until the DDT in the soil has disintegrated.
Elms v. Robms. Death chains of this sort are fortunately not common. A report published by the Wilson Ornithological Society says that most spraying does little damage to most birds, and still less to wild mammals. Fish are more sensitive; when certain insecticides are washed into streams or lakes, they are apt to kill everything that moves on fins. Perhaps the worst effect on birds is the reduction of edible insects, which are important food for many species. But the damage is not complete; not even Miss Carson can point to a single sizable sprayed area where "no birds sing."
To answer insistent complaints, the National Academy of Sciences sponsored a careful study of pesticide damage to wildlife. Its conclusion: the damage, though always regrettable, is not disastrous, and the damaged wildlife population generally recovers in a few years. Sometimes it may be necessary, remarks the Academy, to choose between elms and robins, both of which have their partisans.