Tag Archives: Silent Spring

Rachel Carson’s Silent Spring – Part 3

Following on from part 1 and part 2 in a series of summarised points about pesticide use presented in Rachel Carson’s book, Silent Spring. For some practical advice on smart biological controls in your garden to reduce pesticide use, check out Daphne’s Dandelions.

Beyond the dreams of the Borgias

The build up of chemicals due to recurrent exposure can have disastrous cumulative effects on individuals’ health. While many pesticides are labelled as safe, they often cannot account for the effects of multiple uses, or the effect of the interaction with other chemicals, or indeed the concentrations that can be achieved when combined with the use of neighbours and the wider community. Many of the tests are conducted in highly artificial lab conditions on rats whose diets are carefully controlled – very unlike the human diet.

Some farmers have been known to use pesticides that exceed the amount legally allowable on many foods, and there is often little protection afforded to the consumer in this regard.

Government departments that test foods are often underfunded and understaffed so that only a very small percentage of food sold is actually tested [additional comment: this appears to be the case in New Zealand as well]. When it is found to be dangerous, often nothing is done to warn the public or recall the product from the shelves, due to local and national laws that limit the powers of the related agencies. In cases where products have been withdrawn, it is after the fact and the damage has already been done.

A brilliant quote to summarise: “to establish tolerances is to authorize contamination of public food supplies with poisonous chemicals in order that the farmer and processor may enjoy the benefit of cheaper production – then to penalize the consumer by taxing him to maintain a policing agency to make certain that he shall not get a legal dose. But to do the policing job properly would cost money beyond any legislator’s courage to appropriate, given the present volume and toxicity of agricultural chemicals. So in the end the luckless consumer pays his taxes but gets his poisons regardless.” (p. 183, 2002 edition)

The human price

While some chemicals are known to be safe for humans, sometimes this is due to an enzyme in the body which may lessen its harm. However, if this enzyme is disabled due to contact with other chemicals, then the body’s defense is severely compromised. Since, in day to day life, humans come into contact with a wide range of chemicals, the risks of some chemicals that have been established as “safe” may be heightened from prolonged exposure to a range of chemicals (not necessarily other pesticides even, but food additives or natural substances), whose interactions cannot always be predicted.

The ability to directly point to any one chemical as the cause of particular symptoms is compromised by varying responses of individuals to such chemicals.

One in every four

It is becoming clearer that cancer can be caused by various environmental factors. While Carson does not try to prove that DDT based pesticides directly cause cancer in all individuals, she notes that, based on the knowledge of cells and what causes cancerous cells, and the knowledge of the effects of DDT pesticides, their use should be extremely limited given the potential cause-and-effect relationship. Cleverly, she addresses a question many may ask: why not just look to cures for cancer? She cites Dr Hueper, a cancer researcher who has also had much experience with patients. While treatment is obviously necessary, prevention can be far more effective and cause far less damage to individual health in the first place.

Nature fights back

While some chemical attacks can be effective on the target insect, often this paves the way for other pests to invade as the natural checks and balances of the new pest have been upset by chemical spraying. Sometimes the new pests or species resistant to the chemicals that have flourished in the absence of other insects can be dangerous not just to plants, but to humans and livestock.

While biological controls offer effective and low-cost alternatives to chemical spraying, they are incredibly rare. This is often because large chemical companies support research in Universities on pesticides, but not biological controls. This creates a wealth of attractive scholarships and staff positions. Biological control studies on the other hand are often underfunded, thus salaries are often low and positions few. Many of the leading entomologists on the other hand have had their entire research repertoire sponsored by the chemical industry.

While chemical sprays are not altogether ineffective, optimal results are actually achieved when they are applied sparingly and at the appropriate time, as they do not upset the natural predators and other checks on a pest. Chemical companies often have little motive to inform farmers of this fact.

The rumblings of an avalanche

Pest resistance is becoming an increasing problem, because unlike humans, insects can become resistant to a chemical in the period of two months to several years. Carson illustrates the problem with a few alarming statistics: “Before 1945 only a dozen species were known to have developed resistance to any of the pre-DDT insecticides…resistance began a meteoric rise that reached the alarming level of 137 species in 1960.” The problem of resistance was especially acute with vector (disease carriers) control programmes. Additional note: The problem is analagous to bacterial resistance through the excessive and unnecessary use of antibiotics for humans and animals, and anti-bacterial cleaners. In New Zealand, antibiotic resistant bacteria was a virtually nonexistent problem in 1999, but in 2008 an estimated 5000 cases were evident, according to the Institute of Environmental Science & Research. Read the full NZ Herald article for more, or google “superbugs”.

While DDT is still used in controlling disease-carrying pests (vectors), Carson argues that their use often exacerbates the problem by simply giving way to resistant strands, and notes several areas in which this is becoming an issue: mosquitoes carrying malaria, bacteria carrying houseflies, and body lice. Often vector populations actually increased after being treated with DDT pesticides, and one wonders why they are still used to control mosquitoes in the developing world today.

Due to the fast development of resistance to chemical pesticides, their use is not only futile but economically inefficient. Acquiring stockpiles of the latest miracle pesticide carries the very real risk of it being useless in a very short amount of time, yet great investment can be required for those relying on its properties.

The other road

In this chapter Carson describes an array of biological controls that could be used, and have been used with great success under certain conditions, with fewer ecological and sometimes economic, costs. What she stresses is that each is a biological approach that is “based on an understanding of the living organisms they seek to control, and of the whole fabric of life to which these organisms belong.”

The controls she mentions include:

The breeding and releasing of sterilized male insects, which was successfully used to control the screw-worm fly.

The introduction of a disease, bacterial or viral, to the target species’ environment, such as the bacillus thuringienis which causes fatal septicemia in the larvae of the flour moth. Damage to crops is far less than chemical sprays as the insects have less time to develop, and the diseases are often species specific so they don’t harm other living creatures, or if they do, it is much smaller in number.

The introduction of predatory or parasitic animals that attack or consume the target pest, as was used to control the gypsy moth, Japanese beetle, scales and mealy bugs. This method is used in many planted European forests, where they go so far as to build homes for woodpeckers.

Using or manufacturing the secretions of insects, such as the manufacture of a fake pheromone (sex hormone) to confuse male insects and prevent them from finding mates. This has been used in some cases such as the gypsy moths. Sometimes attractants are used in combination with poisons, but instead of spraying the whole lot over vast areas of land, the chemicals are administered to pieces of fiberboard, which are then scattered on the affected area. These pieces are unlikely to be eaten by other wildlife, and the residues are quickly dissipated, thus not contaminating soil or water.

The use of sound, such as the playing of female mosquito noises at a charged grid that zaps mosquitoes on contact. Repellant noises are also a potential avenue of research.

A quote which summarises the key messages in Carson’s book well:

“Through all these new, imaginative, and creative approaches to the problem of sharing our earth with other creatures there runs a constant theme, the awareness that we are dealing with life – with living populations and all their pressures and counter-pressures, their surges and recessions. Only by taking account of such life forces and by cautiously seeking to guide them into channels favorable to ourselves can we hope to achieve a reasonable accommodation between the insect hordes and ourselves. The current vogue for poisons has failed utterly to take into account these most fundamental considerations.”

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Rachel Carson’s Silent Spring – part 2

Following on from part 1 in a series of summarised points about pesticide use presented in Rachel Carson’s book, Silent Spring.

Rivers of death

Fish and their migration patterns are often disturbed as a result of aerial spraying or runoff from farms, due to several reasons:

  1. Their food stocks (particularly insects for salmon) are killed off, perhaps not necessarily intentionally as they may not be the target insect. These food stocks often take years to rebuild, exacting long term effects on the fish and the other organisms that the affected animals interact with.
  2. The chemicals get into the water, causing the fish themselves to die or become ill or blind as a result of direct chemical exposure.

The reduction of the fish supply affects not only the sport of fishing (as the dead fish are usually unfit for human consumption) but the livelihoods of many populations who depend on fish for their income or need the fish as a key source of protein for where they live.

Many specific kinds of fish have adapted to certain areas over many years and thus their eradication leads to the complete extinction of whole species.

Those chemicals that are washed off by rain are often used repeatedly by farmers to protect certain crops, and these repeated sprayings lead to increased concentrations of chemicals in the water, through runoff.

Some chemicals stay in the water even after extensive flushing and draining, as they can become absorbed into the mud of the bottom of ponds for example.

The manufacturing of pesticides also entails pumping large amounts of chemical waste into nearby waterways that may surround the producing factories. Such disposal is often commonplace and perfectly legal.

Attempts at re-stocking fish after such chemical spraying must often be payed for by the state (ie, taxpayers). Moreover, it is often the state that funds such spraying in the first place.

The chemical-induced death extends not only to fish – it also extends to those animals who eat the dead or dying creatures, and poison them, too. At sea for example, these predators include birds, and they perform important ecological functions on the seaside landscape.

In almost all cases of widespread death of a certain species of fish, for example, it is clear the cause is from pesticide use, rather than disease. This fact is confirmed not only through tests which reveal the animals have no disease, but the behaviour of the sick animals and presence of the chemicals in the relevant tissues of the animals. Furthermore, populations that live side by side can be used for reference – unsprayed areas for example exhibit far less, if any, population decrease, than sprayed areas.

Even low concentrations of pesticides can cause harm to animals who have less tolerance than the intended target species. For example, while insecticide use is sometimes measured in parts per million, shrimp are tolerant of pesticides below levels of parts per billion.

Herbicide runoff from roads further endangers the life of plankton, which threatens the lives of many creatures that feed on it and in turn, those creatures’ predators.

While some animals such as mollusks can survive some chemical exposure, they still store (and concentrate) the chemicals in their organs and tissues, which is particularly alarming if they are meant for human consumption.

In their long periods of transit, the toxicity of these discharged chemicals changes, and there is no predicting whether they will become more or less toxic. Funds for research in these areas have been consistently low, yet extensive research is needed to determine the consequences of pesticides’ interaction with other chemicals in the water and natural environment. Despite the lack of funding for this, vast sums are spent on research developing the pesticides in question.

Indiscriminately from the skies

While many insects that have become the targets of spraying have posed few problems (both financially and for the average citizen), aerial sprays indiscriminately administer pesticides wherever the planes fly over. Citizens have little to no say over whether they wish to be sprayed.

Much of the negative effects of targeted insects has been hugely exaggerated, as has been the response. Sometimes, sprays are used in a preventative manner, before the targeted insect even becomes a nuisance. Other times, spraying is conducted even after successful attempts have been made to control the populations of the target insect through more natural controls (such as the introduction of specific parasites and predators). Often local complaints on behalf of citizens and conservationists have been ignored in such cases. Furthermore, even when it is clear certain kinds of insects will not pose a problem to populations in cities for example, spraying is conducted there nonetheless. Finally, some insects have been targeted that aren’t even at the top of local lists that prioritize certain insects’ elimination.

Those who recognise the toxicity of pesticides about to be aerially sprayed and specifically request their property not to be sprayed, while also promising to take care of the target pest on their own budget, are often ignored. The sprays cause damage to crops or livestock and render the produce either unusable or sold at reduced prices.

When contracts for aerial spraying are awarded to private companies (which they often are), the companies themselves can often be untraceable, so in the case of damages caused by spraying, it can be difficult to find those responsible. This can happen even when there is a legal obligation for the spraying company to register with state officials.

Huge publicity campaigns have been undertaken by the USDA to first exaggerate the threat of a particular insect (Carson uses the example of the fire ant), which contradict with views expressed in its own publications and the studies of scientists who researched (in field studies AND lab studies) the insect in the town it was most prevalent in. The fire ant specifically was noted for its importance as a predator for other more threatening insects. The mounds that it built also helped the soil by aerating it. However, despite its ecological importance, established by University departments and experts, the campaign (substantiated by conversations with farmers and older research) raged on. Though the ant is known to deliver a painful sting, the number of deaths by bee or wasp sting outnumber the deaths by fire ant sting by 33 to 1. Meanwhile, trade journals were celebrating the “sales bonanza” that pesticide makers experienced.

As well as being exposed to aerial sprays, citizens are likely to consume more pesticides via animal products (dairy and milk products) and other vegetables that are inadvertently sprayed. The effects of the combination of farmer’s sprays and other sprays mandated by local governments is unknown.

The fact that many pesticides make it through to animal products for human consumption is particularly worrying when the pesticide is known to increase in toxicity or concentration once it spends a certain amount of time in an animal.

Much aerial spraying is expensive, damaging, and yet, the least effective in controlling the intended pest. Despite this it was repeatedly used when cheaper, more effective, and less damaging methods were known and used before.

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Pesticide use & Rachel Carson’s Silent Spring – part 1

On reading Rachel Carson’s Silent Spring, several timeless conclusions can be drawn about pesticide (insecticides or herbicides) use. Carson, intelligently, did not argue against the use of pesticides point blank, but pointed out the limits of relying solely on chemicals to control pests without considering their wider effects on the balances in nature and human health. Due to this narrow focus, the use of chemical pesticides have sometimes not only been futile, but have exacerbated pest problems.

I’ve tried to keep most of the points general, because Silent Spring mostly addressed DDT pesticides. DDT pesticides are no longer used today except for treating disease carriers, known as vectors (so it is still used on mosquito nets in an attempt to stave off malaria, for example). That’s why some of her points directly aimed at DDT are not included. Originally I intended for this to be one post, but it ended up being a little long, so I’m going to do this in sections. If you know more than me and I’ve written something stupid, let me know. I admit I’m not a scientist, although I appreciate that Carson wrote very accessibly, which is what made this book so important. Points are ordered in chapters, starting from the first to the last.

The obligation to endure

Insect problems have arisen due to the intensification of agriculture that devotes many acres to a single crop. Prior to such intensification, serious insect problems were rarely encountered by farmers. Single crop farming may be economically beneficial to a few, although it does not “take advantage of the principles by which nature works,” as we will see. Logically though, an insect that lives on wheat for example can increase its numbers far more easily if it’s in a field full of wheat, as compared to a field with other plants it is not interested in.

Another reason for the new insect problems is the ever increasing movements of people, who introduce new insects to new areas, which lack the predators that control it in its original habitat.

While there are many specialists working on the problem, many fail to see the it from a holistic perspective, and this myopic view of nature is continued at our own peril.

Surface waters and underground seas

Chemicals inevitably find their way into waterways, where a “mixing” of otherwise “safe” chemicals can create new toxic chemicals that chemists would not deem suitable for human or animal consumption.

Earth’s green mantle

The destroying of various kinds of plants labelled as “weeds” using chemical treatments also has consequences for all other creatures and plants that have a relationship with that plant. For example, animals that depend on the target plant for food, other plants that flourish alongside the target plant, and the particular soil and climate of the region that the target plant flourishes in as a result of many years of evolution – all these are affected when the target plant is suddenly removed. The new plants which take their place (usually crops useful to humans) are often not well adapted to the particular climate or soil, thus they will require further additions of chemicals (either to remove subsequent insect, animal or plant pests, or to add the necessary nutrients to the soil).

Some imported insects, whose food source consists of specific kinds of weed, have been used to control some weeds.

Needless havoc

Insecticides affect other animals that eat the poisoned insects, such as birds. Thus, while certain chemicals may be established safe for some kinds of insects, the effects on the wider food chain may not be known until it is too late.

Alternatives such as introduction of bacterial, fungal or viral infections that only affect the target species are not only more effective at controlling the populations of pests, they have fewer side effects for predatory animals and often only need to be used once rather than requiring re-spraying. Introduction of predatory animals can also be cost effective. For example, if an introduced pest becomes a threat or nuisance, the importation of the pest’s natural predator in its country of origin and its introduction in the new location can be effective in controlling the original pest.

And no birds sing

Insecticides rendered as “safe” by chemical manufacturers are often tested on domesticated animals rather than wild animals, and the tests are done in labs. Thus, the effect on wider species may not be known unless field tests are conducted or the chemical is applied in a natural setting.

Many DDT-based insecticides cannot be removed by rainwater, thus, their effects last multiple seasons.

Sprays can be economically inefficient for several reasons:

  1. Due to the unintentional poisoning of various other animals through the food chain, natural predators of the target pest can be eliminated, thus destroying the natural limits on the pests’ spread. Furthermore, even if some animals do not die due to ingestion or exposure to the chemicals, their reproducing capacities or other functions crucial to their survival, are negatively affected.
  2. Due to the above phenomenon, multiple sprayings are required, as natural controls on insect populations are adversely affected

Often the widespread need for chemical sprays to control pests that affect a particular kind of plant arise from the lack of diversity of the plants. It is noted that having a variety and diversity of plants in a particular area reduces the likelihood of pests from causing widespread damage and thus the need for major spraying, as the severity of damage is not as wide.


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