Population and environment: the evolution of the debate between optimists and pessimists

The potential adverse effects of rapid population growth on human welfare and our natural environment have been the subject of lively debate since the time of Thomas Malthus. This debate has often been contentious with pessimists arguing that population growth has extensive harmful impacts and optimists claiming that advances in technology and smoothly operating markets can take care of society's needs without irreversible damage to the environment. This essay summarizes the evolution of the positions of pessimists and optimists after the middle of the 20th century. From the 1950s to the late 1970s the international discussion of population and environment was dominated by concern about the potential negative impact of rapid population growth in the less developed world and by the feasibility of policy options for reducing the pace of growth. A reversal of this consensus occurred in the 1980 and 1990 s leading to a revisionist view that population growth was at best a minor problem. However, by the turn of the 21st century a broader population policy agenda evolved that included not only renewed interest in the unfavorable effects of population growth but also in other issues such as climate change, international migration, and rapid urbanization. A concluding section discusses the reasons why we don't agree. Continuing disagreements between optimists and pessimists are now less about scientific facts and more about a host of economic, ethical, aesthetic, and political questions.