Her revelations about DDT must have been surprising to those who believed it represented a progressive step forward for humanity, especially when the consequences for the environment were unintentional.
Challenging the chemical industry
Carson’s willingness to speak up against the chemical industry that produced compounds such as DDT was courageous. At a time when the environmental movement was only beginning, detractors argued she cared more about birds, fish, and insects than the health of human beings. After all, human food security and protection against diseases like malaria or typhus were positive goals – who could deny that? The chemical industry, no doubt genuinely trying to provide useful substances for humanity, was threatened by her work. Upset by her book, some critics also chose to attack Carson personally rather than address her scientific concerns, attempting to portray her as a hysterical spinster and perhaps even a communist.
However, Carson showed that DDT wasn’t even helping humans as intended. She claimed that due to the overuse of pesticides, insects were developing something known as “resistance.” Resistance works like this: if a poison such as DDT wipes out weaker insects, any survivors would be likely able to survive a future spraying — and so might their offspring. What was at first an effective bug killer could shortly become useless as insects evolved to resist the pesticide. Those survivors would then go on to repopulate and, before long, the unwanted bugs would be back, only stronger.
Resistance itself is not new or unusual. Insects have been developing the ability to endure natural plant toxins for hundreds of millions of years. But man-made toxins can increase the speed and scope in which insects can evolve. The counterintuitive lesson of pesticide resistance is that to maintain some ability to control insects, only a small amount of pesticide should be used. Otherwise, any victories achieved could be short lived as harder-to-kill bugs take the place of their more susceptible cousins.
Seen from this angle, Carson was far from being at war on human welfare. She encouraged us to use less spray, not only because it would be better for the environment, but because it would likely be better for us in the long run. In Silent Spring, she gave evocative examples of places where the insect problem was worse after pesticides had been sprayed. For example, in apple orchards in Virginia and Nova Scotia, apple-eating moths became more problematic after DDT had been used.
Despite her concerns about DDT, Carson never called for its outright ban and was not inherently opposed to pesticides. Her real concern was of a coming “Age of Resistance,” in which increasingly toxic chemicals were used less effectively against insects, resulting in environmental havoc, harder-to-kill bugs, and the need for more potent chemicals.
A better future
Carson’s detractors may have thought she was overly sentimental about nature — she did write movingly about the plight of natural creatures — but she was also an excellent scientist who supported her claims with carefully compiled evidence. Like any good scientist, she provided a list of references at the end of her book, citing the work of many other biologists and researchers. If the mild-mannered Carson was “emotional,” then so were a whole body of scientists who were reaching the same conclusions. Carson denied being an emotional crusader but maintained that she was merely collecting the facts so that the public could make up their own minds about pesticides in an informed manner.
