Environmentalists devote little attention at the moment to the size and growth of the human population. To counter this neglect, the monograph (i) includes original graphs showing population size and growth since 1920 in the world as a whole and the United States; (ii) assembles evidence tying the increasing number of people to ecosystem deterioration and its societal consequences; and (iii) analyzes sample-survey data to ascertain whether the current disregard of population pressures by U.S. environmentalists reflects the thinking of Americans generally. However, even if a nation took steps primarily intended to lower childbearing and immigration, the findings of social science research indicate that the steps would not have a substantial, lasting impact. The discussion, which suggests an indirect way by which government may reduce fertility, underlines for environmental scholars the importance of studying their subject in a multidisciplinary, collaborative setting.