“We stand now where two roads diverge… The road we have long been travelling is deceptively easy, a smooth super-highway on which we progress with great speed, but at its end lies disaster. The other fork of the road – the one ‘less travelled by’ – offers our last, our only chance to reach a destination that assures the preservation of our earth.”
Thus wrote Rachel Carson in her best selling book ‘Silent Spring’, published back in 1962. ‘Silent Spring’ is largely credited as the catalyst that began the environmental movement and (eventually) the formation of the US Environmental Protection Agency.
In the book, Ms Carson writes about the widespread use of chemical pesticides and the negative effects they can have on biodiversity. In particular she highlights how aerial spraying of DDT led to a collapse of local bird populations – hence the book title.
Although dated, the book has some useful lessons for us all. The first, and most obvious, is that if you are a hammer everything looks like a nail. Chemical pesticides largely came out of research during World War Two into chemical warfare. Once the war ended, scientists used the knowledge that they had acquired to use chemicals to kill insect pests rather than humans.
In this sense, chemical pesticides have a similar history to nitrogen fertilizers. As Michael Pollan writes in The Omnivore’s Dilemma, the US government found itself at the end of World War II with a surplus of ammonium nitrate, the principal ingredient in making explosives. Ammonium nitrate is an excellent source of nitrogen for plants, and the chemical fertilizer industry was the product of the government’s effort to convert its war machine to peacetime purposes.
In her book, Ms Carson writes of a USDA programme in 1958 to exterminate the fire ant, an insect that has a sting similar to that of a bee or a wasp. A million acres were sprayed in Florida and Louisiana with dieldrin and heptachlor, two relatively new chemicals many times more toxic than DDT. The results on wildlife, particularly birds, as well as on livestock, mainly pigs and chickens, were catastrophic. The poisons also accumulated in cow’s milk.
Spraying continued for the following two years but without any meaningful impact on the fire ant population. It appears that the pesticide only killed off the weaker fire ants but left the stronger ones alive to adapt and develop an immunity to the poisons. Ms Carlson likens it to human-induced Darwinism.
So that is the second lesson from the book: because nature constantly adapts, pesticides become increasingly ineffective. You either have to apply them in greater concentration or constantly develop new ones.
The third lesson is that everything in nature is related: try to solve one problem and you may create a worse one. As the author writes, ‘nothing in nature exists alone’. She gives the example of the US Forest Service’s use of DDT for combating the spruce budworm in 1956. The pesticide was successful in eliminating the spruce budworm but also killed off the natural predators of the spider mite, whose population then exploded to become an even worse problem.
Finally, Ms Carlson makes the point that, once they have been applied, these pesticides do not disappear, but build up in dangerous quantities in the soil, in earthworms, in the fish in the adjoining rivers and lakes, and in livestock. They then work their way along the food chain in surprising and dangerous concentrations. The spring was silent in 1962 because the birds had died after eating earthworms poisoned with DDT.
The world is a different place now than it was when Ms Carlson wrote her book 58 years ago. However, as the current ruckus surrounding glyphosate shows, the issues remain. The general public, including jurors, do not trust scientists. They believe that they are either in the pay of big chemical companies, or that they do not have sufficient data over a long enough period of time to evaluate a product’s safety. This distrust began with Silent Spring.
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