Discussion on Population Growth and Climate Change Effects

At the Woodrow Wilson International Center for Scholars Environmental Change and Security Program presentation on Population and Climate Change: Relationships, Research, and Responses, Brian O’Neill, Scientist and Director of the Population and Climate Change Program, said some examples of human impact on the environment are forests dwindling, fisheries collapsing, cropland shrinking, large water shortages, and global warming.

The United States, he said, is the world’s largest greenhouse emitter. However, the Population Reference Bureau 2007 World Population Data Sheet forecasts that Africa will grow by 107% by 2050. Lack of access to and use of family planning, he said, is an important cause of population growth in Africa and other areas of the world.

From health surveys, it seems that there is an unmet demand for contraceptive use. Unintended pregnancy, O’Neill said, is the factor in continued population growth that is “the most amenable to program and policy intervention.” Worldwide, 80 million pregnancies (38% of all pregnancies) are unintended.

O’Neill said that the cost of inaction will be high, because if today’s birth rates remain unchanged, world population will grow from 6.7 billion to 11.9 billion by 2050, which would undermine efforts to preserve the natural environment.

Joseph Speidel, Adjunct Professor, Department of Obstetrics, Gynecology & Reproductive Sciences, University of California, said slowing population growth would reduce greenhouse gas emissions, and although not noticeable immediately, by the middle of the century there would be significant results. Population-related policies can be considered “win-win” in respect to climate change, he said. With a lower population size, CO2 emissions would be lower as well.

Recent analysis of historical data, Speidel said, supports a “roughly proportional direct effect of population size on emissions.” Scenarios of future emissions have not explicitly investigated the implications of slower population growth, but that preliminary work indicates that effects of aging and urbanization may significantly affect the outlook for future emissions. How much less costly, he asked, would long term climate change goals be if we could assume a lower population in the future?