I have grown weary of listening to radio and TV new announcers discuss the human population problem. I think a primer of a few principles of population arithmetic might be useful to remind us where we ecologists sit in these discussions. The problem centres on the issue of eternal growth and then the transition of any population from a growing one to a stable one. I concentrate here on human populations but the results apply to any long-lived species.
I list four empirical principles of demography.
- No population can continue growing without limit. This generalization is rock solid, so it would be good to keep mentioning it to sceptics of the following generalizations.
- Populations grow when births and immigration exceed deaths and emigration. If we consider the entire global human population, emigration and immigration disappear since we have not yet colonized space. Populations stabilize when births equal deaths.
- A population that moves from a growth phase to a stable phase must change in age structure. Every stable population must contain fewer young persons and more older persons.
- These changes in age structure have enormous implications for our requirements for hospitals, doctors, schools, teachers, and social support agencies. These changes are almost completely predicable for humans and should not come as a surprise to politicians.
- Pushing the panic button because a particular population like that of Japan is stabilizing and could even decline slightly may be useful for economists wishing for infinite growth but should be recognized as an expected event for every country in the future.
The bottom line is that we have the knowledge and the ability to plan for the cessation of human population growth. Many good books have been written to make these points and we need to keep repeating them. That many people do not understand the simple arithmetic of population change is a worry, and we should all try to communicate these 5 simple principles to all who will listen.
Cafaro, P., and Crist, E. 2012. Life on the Brink: Environmentalists Confront Overpopulation. University of Georgia Press, Athens, Georgia. 342 pp. ISBN: 978-0-8203-4385-3
Daly, H.E., and Farley, J. 2011. Ecological Economics: Principles and Applications. 2nd ed. Island Press, Washington, D.C. 509 pp. ISBN: 978-1-5972-6681-9
Washington, H. 2015. Demystifying Sustainability: Towards Real Solutions. Routledge, New York. 222 pp. ISBN: 978-1138812697