How one scientist took on the chemical industry - Mark Lytle

434,161 views ・ 2020-03-17

TED-Ed


Please double-click on the English subtitles below to play the video.

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In 1958, Rachel Carson received a letter
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describing songbirds suddenly dropping from tree branches.
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The writer blamed their deaths on a pesticide called DDT
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that exterminators had sprayed on a nearby marsh.
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The letter was the push Carson needed to investigate DDT.
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She had already heard from scientists and conservationists who were worried
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that rampant use of the pesticide posed a threat to fish, birds,
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and possibly humans.
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She began to make inquiries through government contacts
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from her years working in the United States Bureau of Fisheries.
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She asked: “what has already silenced the voices of spring?”
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In 1962, Carson published her findings in "Silent Spring."
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Her book documented the misuse of chemicals
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and their toll on nature and human health.
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"Silent Spring" immediately drew both applause and impassioned dissent—
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along with vicious personal attacks on the author.
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How did this mild-mannered biologist and writer ignite such controversy?
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Carson began her career as a hardworking graduate student,
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balancing her studies in biology at John Hopkins University
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with part time jobs.
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Still, she had to leave school before completing her doctorate
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to provide for her ailing father and sister.
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Carson found part time work with the Bureau of Fisheries
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writing for a radio program on marine biology.
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Her ability to write materials that could hold the general public’s attention
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impressed her superiors, and in 1936,
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she became the second woman to be hired at the Bureau full time.
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In 1941, she published the first of three books on the ocean,
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combining science with lyrical meditations on underwater worlds.
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These explorations resonated with a wide audience.
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In "Silent Spring," Carson turned her attention
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to the ways human actions threaten the balance of nature.
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DDT was originally used during World War II to shield crops from insects
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and protect soldiers from insect-borne diseases.
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After the war, it was routinely sprayed in wide swaths to fight pests,
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often with unforeseen results.
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One attempt to eradicate fire ants in the southern U.S.
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killed wildlife indiscriminately, but did little to eliminate the ants.
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In spite of this and other mishaps, the US Department of Agriculture
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and chemical companies extolled the benefits of DDT.
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There was little regulation or public awareness about its potential harm.
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But Carson showed how the overuse of chemicals
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led to the evolution of resistant species—
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which, in turn, encouraged the development of deadlier chemicals.
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Since DDT does not dissolve in water,
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she asserted that over time it would accumulate in the environment,
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the bodies of insects, the tissues of animals who consume those insects,
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and eventually humans.
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She suggested that exposure to DDT might alter the structure of genes,
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with unknown consequences for future generations.
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The response to "Silent Spring" was explosive.
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For many people the book was a call to regulate substances
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capable of catastrophic harm.
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Others objected that Carson hadn’t mentioned DDT’s role
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controlling the threat insects posed to human health.
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Former Secretary of Agriculture Ezra Taft Benson demanded to know
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“why a spinster with no children was so concerned about genetics?”
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and dismissed Carson as “probably a Communist.”
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A lawyer for a pesticide manufacturer alluded to Carson and her supporters
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as “sinister influences” aiming to paint businesses as “immoral.”
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In reality, Carson had focused on the dangers of chemicals
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because they weren’t widely understood, while the merits were well publicized.
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She rejected the prevailing belief that humans
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should and could control nature.
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Instead, she challenged people to cultivate
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“maturity and mastery, not of nature, but of ourselves.”
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Carson died of cancer in 1964,
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only two years after the publication of "Silent Spring."
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Her work galvanized a generation of environmental activists.
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In 1969, under pressure from environmentalists,
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Congress passed the National Environmental Policy Act
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that required federal agencies to evaluate environmental impacts of their actions.
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To enforce the act,
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President Richard Nixon created the Environmental Protection Agency.
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And in 1972, the EPA issued a partial ban on the use of DDT.
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Long after her death, Rachel Carson continued to advocate for nature
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through the lingering impact of her writing.
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