Silent Spring: The Reckoning

Rachel Carson’s Silent Spring, a prophetic warning of the deleterious effects of pesticides such as DDT on the environment, was published in 1962. The book warned that the widespread use of pesticides was devastating bird populations, and that if such use was not eliminated or reduced, many species would become extinct. Carson detailed how DDT caused birds to lay eggs with shells so thin and fragile they broke before the embryos could develop into live chicks; birds of prey were especially affected because in their role as top predators, DDT became more concentrated in their bodies. At the time of publication, bald eagles had declined to near extinction because of the thin-shelled egg problem. Fortunately, despite heavy criticism by vested interests, Carson’s message was heard, DDT was banned, and the bald eagle has recovered, as have other raptors.

One would hope that the lesson had been learned and that similar mistakes would no longer be made. But nothing of the kind has in fact happened, despite all the earth days, demonstrations, supposed regulations, and lip service. A particularly striking and pertinent example of our failure to practice what we preach is the impending fate of the Monarch butterfly, that wonder of the insect world. This remarkable creature spends the summer months spread out in the northern United States (primarily in the upper Midwest) and southern Canada and winters concentrated in its millions in a small area of central Mexico. Even more amazing, this yearly migration covers multiple generations of the species, so that the butterflies that leave Mexico in the spring are not the same individuals who arrive in the north weeks later (they reproduce on the way), and a new generation leaves the north to return to Mexico in the fall. Yet they return to the same groves that their great-great-grandparents left months earlier!

Alas, the Monarch has one trait that has long served it well but which is now its Achilles’ heel: they lay their eggs on, and their caterpillars eat, only milkweed. They absorb the nasty taste of the milkweed, rendering them unpalatable to insect eating birds, which protects them from predation on their long, multigenerational migrations. Should the milkweed decline or disappear, so too will the Monarch.

Which is exactly what appears to be happening. Scientists and amateurs alike have noted a steady decline in the numbers of Monarchs gathering each year in Mexico (the best place to get a handle on their numbers), and this year (2013) the population has declined precipitously. According to a recent article in the New York Times, in 2012 the numbers of butterflies at the Mexico wintering site was approximately 60 million, itself a decline from previous years; but this year, only 2 million have showed up, and they showed up a week later (more on the implications of this fact later). Imagine if the human population had dropped from its current 7 billion to less than 300 million in just one year.

The most likely cause of this decline is the rapid disappearance of milkweed along the routes followed by the butterflies as they move north and south in their annual journeys. The American Midwest, that famous breadbasket to the world, is increasingly covered with corn and soybean fields, a large percentage of which are planted with so-called “Roundup ready” varieties, i.e., varieties that have been genetically engineered to resist glyphosate, the active ingredient in Roundup brand herbicide. Milkweed and other native species are not genetically engineered to resist that poison, so they die while the corn and soybeans prosper. With insufficient milkweed available on which to lay their eggs, Monarchs cannot renew their numbers, so they also die.

Likely compounding the problem is global warming. Canadian scientists have observed that many Monarchs are migrating further north than in the past, well past the natural range of the milkweed. While adults can feed on the flowers of other species, they can lay their eggs, and the caterpillars can dine, only on milkweed. Thus those Monarchs who went too far north (probably because of temperature) could not successfully reproduce. Warming may also explain why Monarchs arrived a week late in Mexico.

The phenomenon of crops genetically engineered to resist manmade herbicides is an example of System run amuck. System operates on the erroneous belief that a “problem” is singular and that its solution is also singular. So, if “weeds” are “invading” your crops, getting rid of them will take care of that problem. (Note: How can native species be invading on non-native, and artificial, varieties? Aren’t corn and soybeans invading on the native species? Aren’t corn and soybeans therefore the true weeds?) How very ironic that our capitalist system seems to be imitating a communist dictator: Chairman Mao once ordered that all sparrows be killed because they stole grain; consequently, crop-eating insects increased in numbers so sharply that he ordered widespread spraying of insecticides. Result: The elimination of pollinating species, particularly honeybees. If the Monarch is in such dire straits, are not other, likely beneficial species along its route also threatened? At the same time, some not so beneficial “weed” species are developing resistance to glyphosate, and it is likely that in the not so distant future, glyphosate herbicides will be rendered useless while some other pestilence will discover the vulnerabilities of genetically engineered crops. Thus the solution will turn out to be yet another of mankind’s many self-made problems.

See also this more recent article.

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  • Chi O. Allison  On February 4, 2014 at 12:03 AM

    Not every species that escapes into the wild will be a problem. Most crops will simply die out because they can’t compete with hardier wild plants. In one experiment, rapeseed plants, both transgenic and conventional, were grown in a field but never harvested. Scientists then followed the subsequent history of the field for ten years. All the crops declined in numbers from year to year. After the fifth year, none of the genetically modified crops could be found at all, and after ten years there were only a few crop plants of any type remaining in the field.

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