Silent Spring by Rachel Carson was an environmental science book. It documented the negative effects the indiscriminate use of pesticides has on the environment, particularly the birds.
The book became the tool that awakened the public to the real harm that big industrial companies have been hiding from them. Thus, driving them to launch an environmental movement that aims to prohibit the indiscriminate use of pesticides, specifically DDT.
Is is a present tense verb.
Past of is is was and future tense of is is will/shall.
