by DK
DDT proved cheap to produce, highly effective, and at first appeared to pose no threat to human beings. After the war, with the chemical in plentiful supply, its use in agriculture was an obvious next step. With its wide range of apparently safe applications, it must have seemed like a panacea to farmers, who happily sprayed it on their crops, often without the use of masks or protective clothing, because they did not fully appreciate the powerful toxicity of this dangerous chemical compound.
After DDT came a whole host of synthetic agrochemicals, including aldrin, dieldrin, endrin, parathion, malathion, captan, and 2,4-D. Used in conjunction with fertilizers made out of surplus nitrogen that was no longer needed to make explosives, these chemicals enabled the intensification of farming. The chemical age had dawned and by 1952, there were almost 10,000 separate new pesticide products registered with the US Department of Agriculture (USDA).
“No one since [Silent Spring]would be able to sell pollution as the necessary underside of progress so easily.”
H. Patricia Hynes
Raising awareness
Carson was not the first person to notice the harmful effects of DDT. There were a few early dissenters, including nature writer Edwin Way Teale, who warned that a spray with the indiscriminate impact of DDT could upset the balance of nature. In 1945, the director of the US Fish and Wildlife Service (FWS), Dr Clarence Cottam, stated that caution was essential in the use of DDT because the true impact of the product was not yet fully understood. The following year, Fred Bishop, writing in the American Journal of Public Health, stressed that DDT must not be allowed to get into foods or be ingested by accident.
Various scientific studies and reports also raised concerns. For example, in 1945 the US government published a study that found traces of DDT in the milk of cows sprayed with the chemical. It recommended that farmers use “safe alternative substitute insecticides” to control flies and lice on cattle. Carson’s longstanding position as editor-in-chief at the FWS until 1952 meant that she had access to a great many of these reports; she found them to be very disturbing reading.
Since the research was rather scattered and by no means accessible for the general reader, Carson resolved to gather what material she could find and present it in a way that the ordinary non-scientist could understand. As she made progress with the writing of Silent Spring, it became clear to her that she had a moral duty to make the information public. As well as documenting the hazards of indiscriminate pesticide use, Carson dared to suggest that the chemical companies were putting profits before people and that the government might even be colluding with them, knowingly or otherwise, by failing to regulate the industry effectively.
The response from the US chemical industry was predictable. At first, they tried to sue Carson, her publishers, and The New Yorker—which had published a serialization of the book. However, Carson was prepared for this kind of response. She knew the book would be controversial and seen as threatening by the chemical industry. Therefore, as well as meticulously tracking and recording her research—which had been gained from government bodies, her contacts in research institutions, and other reputable sources—she also had the manuscript reviewed by scientists and experts.
When suing Carson did not work, the chemical companies launched a campaign to bring her into disrepute, stooping to personal attacks such as depicting Carson as a “hysterical” cat-loving woman, who was ill-equipped to write such a book. The smear campaign backfired, merely increasing the sales of Silent Spring.
“A spray as indiscriminate as DDT can upset the economy of nature… Ninety percent of all insects are good, and if they are killed, things go out of kilter right away.”
Edwin Way Teale
Organisms higher in the food chain suffer from the impact of DDT the most. In producers, the poison only represents 0.04 ppm (parts per million), but the concentration increases with each step up the food chain. By the time tertiary consumers are involved, levels are high enough to have toxic effects.
“They should not be called insecticides but biocides.”
Rachel Carson
New policies
Notable scientists supported Carson’s findings and US President John F. Kennedy invited her to testify before a Congressional Committee in 1963. She called for new policies that would serve to protect the environment. The Committee released a report entitled “The Uses of Pesticides,” which broadly supported Carson’s book. Inspired by Carson, activists continued to lobby government until in 1972, a decade after Silent Spring was first published, DDT was banned in the US. Other countries followed, although some retain it to control mosquitoes.
The legacy of Silent Spring is greater than the banning of DDT. It demonstrated to industry giants and government the power of an educated public.
After DDT was banned in many countries, Osprey populations—which had declined significantly from the 1940s—began to recover. Ospreys had eaten small animals affected by DDT.
“Man is part of nature and his war against nature is inevitably a war against himself.”
Rachel Carson
A persistent poison
DDT (dichloro-diphenyl-trichloroethane) belongs to a group of pesticides called organochlorides. It kills insects on contact by interfering with their nerve impulses. The compound is fat soluble and is deposited in the tissues of animals exposed to it, either directly or by eating contaminated food. Repeated exposure to DDT results in it building up in the body fat and becoming toxic.
DDT also biomagnifies up the food chain. Humans are susceptible to poisoning from regular exposure to DDT and while the effects of small amounts in the environment are unknown, it has been associated with cancer, infertility, miscarriage, and diabetes. It is now banned in western countries, but studies carried out by the US Center for Disease Control in 2003–4 found DDT or its breakdown product (DDE) in the blood of 99 percent of people tested.
See also: Human activity and biodiversity • Animal ecology • The ecosystem • A holistic view of Earth • Man’s devastation of Earth • Environmental ethics
IN CONTEXT
KEY FIGURE
Gene Likens (1935–)
BEFORE
1667 The corrosive effect of polluted city air on limestone and marble is noted by the English diarist John Evelyn.
1852 British chemist Robert Angus Smith argues that industrial pollution causes the acidic rainfall that damages buildings. He is the first person to call it “acid rain.”
AFTER
1980 The US Congress passes the Acid Deposition Act, undertaking an extensive 18-year research program into acid rain.
1990 An amendment to the US Clean Air Act (passed originally in 1963) establishes a system that is designed to effectively control emissions of sulfur dioxide and nitrogen oxides.
The effects of acid rain on stone were noticed as long ago as the 17th century in England, and in Norway in the 19th century. However, it was not until American ecologist Gene Likens carried out in-depth studies in an area of rural New Hampshire that the phenomenon came to be properly understood.
From 1963 onward, freshwater ecologist Likens and his team studied the relationship between water quality and life forms in the Hubbard Brook drainage basin in New Hampshire. They discovered that the rainfall there was unusually acidic. Acidity, as expressed by pH (potential of hydrogen), ranges from 0 (most acidic) through 7 (neutral), to 14 (least acidic). Most fish and other aquatic animals fare best in water with pH values of 6–8, but Likens found values of 4—too acid for fish, frogs, and the insects they eat to survive. He set up monitoring stations around New England, which showed that acid rain and snowfall were widespread in the densely populated and heavily industrialized northeastern states. Likens’s systematic work persuaded the US government to introduce laws to control emissions of the chemicals responsible for acid rain.
Acid rain had been wearing away stonework—such as this statue in the churchyard of St. Peter and St. Paul, Krakow, Poland—for hundreds of years before th
e phenomenon was understood.
Effects of acid rain
When fossil fuels are burned in power stations and factories, sulfur dioxide (SO2) and nitrogen oxides spew out of their chimneys. Spreading through the lower atmosphere, these gases react with water to produce dilute sulfuric acid (H2SO4) and nitric acid (HNO3). These weak acids fall as rain and enter rivers and lakes, making them more acidic. Increased acidity stresses animals and plants. Water snails disappear, fish eggs fail to hatch, and insects and the frogs that eat them die. Eventually, lakes will not support any life.
By the early 1970s, thousands of lakes in Scandinavia had lost their fish and were virtually dead. By 1984, Brooktrout Lake and others in the Adirondack Mountains, New York, were devoid of fish. Acid rain also leaches harmful aluminum from the soil, and acidic clouds and fog harm plants, reducing their ability to photosynthesize, leading to death.
“We experienced eight years of denial, but that’s not unusual in environmental issues.”
Gene Likens
Emission control
In the 1970s and 1980s, other areas badly affected by acid rain included the “Black Triangle” of Czechoslovakia, Germany, and Poland, where large areas of forest died. Thanks to Likens’s work, stricter controls were brought in after 1990. Scrubber systems that extract SO2 were fitted to power station chimneys with great success. Emissions of the gas were cut by almost half in the US, and by two thirds in Europe. Fish began to return to lakes and rivers. However, the problem of acid rain still blights parts of Russia, China, and India.
GENE LIKENS
Likens was born in Indiana in 1935. After earning a Ph.D. in zoology from University of Wisconsin, he was appointed assistant professor at Dartmouth College. In 1963, with fellow scientists F. Herbert Bormann, Noye Johnson, and Robert Pierce, he began research into the water, minerals, and life forms in the Hubbard Brook basin. In 1968, his studies recorded the widespread prevalence of acid rain, the product of emissions from factories in the Midwest. The team’s work in the area over many years was described as one of the world’s most thorough studies of how air pollution and land use has shaped a drainage basin. Likens’s work on deforestation, land use, and sustainability led to a change in policy by the US Forestry Service. It also helped shape the amended Clean Air Act in 1990. Likens was awarded the National Medal of Science in 2001.
Key works
1985 An Ecosystem Approach to Aquatic Ecology: Mirror Lake and its Environment
1991 Limnological Analyses
See also: Endangered habitats • The legacy of pesticides • Deforestation • Depletion of natural resources • Ocean acidification
IN CONTEXT
KEY FIGURE
Garrett Hardin (1915–2003)
BEFORE
1798 Thomas Malthus forecasts that continued population growth will exhaust global food supplies by the mid-19th century.
1833 In Two Lectures on the Checks to Population, British economist William Forster Lloyd discusses overpopulation, using the example of common land, which is less productive if too many cattle graze it.
AFTER
1974 A United Nations conference in Bucharest creates the UN’s first World Population Plan of Action.
2013 British social geographer Danny Dorling outlines in Population 10 Billion why it is unlikely the world’s population will ever reach that number, contrary to UN estimates.
In 1968, two scientists in the US issued dire warnings about overpopulation. Ecologist Garrett Hardin predicted that Earth’s resources would soon be used up and environmental damage would increase. In The Tragedy of the Commons, he cited examples of several major global crises that had been caused by overpopulation: the destruction of fish stocks by overfishing; the draining of lakes by over-extraction of groundwater for irrigation; deforestation; pollution of air, land, and sea; and species extinction. Hardin himself proposed a controversial solution to the problem of overpopulation, arguing that the government should deny welfare assistance to people who bred “excessively,” to prevent further births. Biologist Paul Ehrlich similarly advocated population control in The Population Bomb, with warnings that human numbers would soon reach a point where mass starvation would ensue.
Ragpickers Court (1879) by William Allen Rogers shows a poor Italian neighborhood in New York City. Such overcrowding allowed diseases to spread through poverty-stricken areas.
Growth and decline
For most of human history, the world’s population had grown only slowly. It began to increase more rapidly in Western Europe and the United States in the early years of the Industrial Revolution, when British economist Thomas Malthus warned of a future famine. His fears, however, proved premature because food production increased more quickly than many expected. Life expectancy also fell in the new industrial cities, due to infectious diseases. It rose again with better healthcare and nutrition, cleaner water, and more rights for workers. By 1924, there were 2 billion people in the world, and by 1960 there were 3 billion, with most growth occurring in the developing countries of Latin America, Africa, and South and East Asia.
This graph plots a comparison between the annual growth rate of the world population and the total population in absolute numbers. The data for the years after 2017 is a projection.
A slowing birthrate
In Europe and North America in the 20th century, wider access to birth control, better education, and more women entering the labor market resulted in lower birth rates. This phenomenon is now being replicated for women everywhere. Although the world’s population passed 4 billion in 1974, 5 billion in 1987, 6 billion in 2000, and 7 billion in 2011, the annual rate of increase peaked near the end of the 1960s at 2.5 percent a year. Populations are still growing quickly in some parts of the developing world, but the trend is not as rapid as it once was. It took just 11 years for the world’s population to rise from 6 billion to 7 billion, but the increase to 8 billion is forecast to be 13 years, then another 25 years to reach 9 billion. The UN forecasts a peak of 11.2 billion in 2100.
Despite the slowing growth, challenges remain. In 2009, a UN report warned that the world would need to produce 70 percent more food by 2050 to feed its extra population, thereby putting more pressure on land, water, and energy resources. Future population growth is also likely to aggravate many environmental problems, such as pollution, and rising levels of atmospheric greenhouse gases, fueling global climate change.
China’s one-child family planning policy
A 1994 poster of a smiling mother and daughter promotes China’s one-child policy. Many baby girls were abandoned or killed so that their parents could try for a son.
Until the 1960s, China encouraged families to have as many children as possible, and the population rose from 540 million in 1949 to 940 million in 1976. However, the government soon became concerned about the demand on resources. In 1978, scientist and politician Song Jian calculated that China’s ideal population was between 650 and 700 million people, and in 1979, his projections led the government to create a new policy limiting couples to one child per family.
This one-child policy was enforced more strictly in urban areas than in the countryside; in some regions a second child was permitted if the first was a girl. In the cities, however, women were forced to abort second children, and in 1983 alone, 21 million women were forced to undergo sterilization. The policy was relaxed in 2015, but the government still only allows two children per family.
See also: Human activity and biodiversity • The Verhulst equation • Depletion of natural resources • Urban sprawl
IN CONTEXT
KEY FIGURE
Franz Hölker
BEFORE
1000 CE The first organized system of street lighting (by oil lamps) is introduced in Muslim Spain.
1792 Scottish-born engineer William Murdock invents the gas light. Over the next half century, many cities introduce gas street lighting.
1879 American inventor Thomas Edison demonstrates the first commercially viab
le electric light bulb.
1976 High-brightness, high-efficiency, LED lights are introduced.
AFTER
2050 The date by which Hölker and others predict that, with the global population set to exceed 9 billion, Earth’s total illuminated area will have doubled since 2016.
According to some ecologists, light pollution—the amount of artificially generated light in the world—could be the most damaging pollutant of all. Around 80 percent of humanity lives under skies saturated with light. In 2017, a major German study of light pollution, carried out by ecologist Franz Hölker and others using satellite data, showed that the area of Earth illuminated artificially grew 9 percent between 2012 and 2016. The brightening is most intense in industrializing countries in South America, Africa, and Asia, but it also continues to increase in the already well-lit countries of Europe and in the US.
Astronomers were among the first to notice light pollution because it interfered with their ability to see celestial objects in the night sky. In 1988, American astronomers Tim Hunter and David Crawford founded the International Dark-Sky Association to protect the night skies from light pollution. It was the first organization of its kind.
