U.S. Sustainability and Population
John R. Bermingham
How can tremendous momentum toward more and more population growth ever be brought to an end?
What can be sustained in America in the face of never ending population growth? Today's population is just a hair over 300 million. The Census' most recent medium projection for 2100-published on the basis of the 1990 census-is 570 million. The 570 million is now trumped and outdated by the massive number of immigrants who have flooded into the country during each of the past fifteen years. If based upon current data, the projection for 2100 would certainly be greater than 600 million and some projections even place our year 2100 total at more than a billion. How can this tremendous momentum toward more and more population growth ever be brought to an end?
Those who hope for a cessation of U.S. population growth must recognize that a population can be stationary only if there is an exact mathematical balance between migrants, births and deaths. The population balance may also be expressed in terms of migrants, Total Fertility Rate (TFR), replacement level fertility, longevity and population. In general terms, TFR is the average number of children born by each woman. A nation's replacement level fertility rate is the number required to keep a population in balance assuming zero migration.
The following table displays a series of mathematically determined migration-fertility-population balances that assume longevity at 79.2 years, (the level expected in 2015) and replacement fertility at 2.1 children per women, (the norm for developed nations). Time is not a factor. The figures hold true regardless of the date that stationarity is achieved.
Choose a column headed by a hoped-for zero growth level. Each total fertility rate in that column will exactly offset the corresponding migration level shown on the left. Achieving any of these fertility-migration-population levels is the key to bringing growth to an end.
What is realistic and when? What does this mean for sustainability?
Conclusion: If zero U.S. population growth is to be achieved prior to a doubling of the current population-with all that a doubling implies for the environment, land use, and historic preservation-very substantial reductions must occur in both immigration levels and U.S. fertility levels. Major socio-economic and political changes will be necessary.
