How large a human population can the earth sustain? Is population growth essential for sustained economic prosperity? Last month, an Ethical Musings' reader inquired whether the US has enough people to support healthcare and other benefit programs for its aging population. Since then, I've given those questions some thought. Here is the second installment (read the first here) of my efforts to grapple with those issues; the third installment will appear in my next Ethical Musings post.
First, the earth has a limited carrying capacity, i.e., the earth can only sustain so many living things (plants and animals of all types). Malthus had that much right. Improved agricultural techniques, distribution of food and water, and other technological advances have stretched and may further stretch earth's capacity, but limits do exist because the earth consists of a finite set of resources. Except for solar energy from the sun, we have no realistic way of importing any material or resource from elsewhere in meaningful quantities nor are we likely to develop such technology in the next one hundred years.
Second, most of the available data confirms that humans are diminishing the earth's capacity to sustain life. 2014 was the hottest year on record. A scientific study released in January 2015 cites evidence showing that we have already crossed four of nine planetary boundaries: deforestation, level of carbon dioxide in the atmosphere, and the flow of nitrogen and phosphorous (both used in fertilizers) into the ocean. (Will Steffen, Katherine Richardson, Johan Rockström, Sarah E. Cornell, Ingo Fetzer, Elena M. Bennett R. Biggs, Stephen R. Carpenter, Wim de Vries, Cynthia A. de Wit, Carl Folke, Dieter Gerten, Jens Heinke, Georgina M. Mace, Linn M. Persson, Veerabhadran Ramanathan, B. Reyers, and Sverker Sörlin, "Planetary boundaries: Guiding human development on a changing planet," Science, 1259855 Published online15 January 2015 [DOI:10.1126/science.1259855].) James Lovelock's 2006 book, The Revenge of Gaia, is a slightly dated but highly readable explanation of how humans have diminished the earth's capacity to sustain life. A crisis point from which there is now return is clearly approaching, though thankfully predictions that we would have reached that crisis point by now have so far proven wrong, e.g., Malthus and the Club of Rome's 1972 report.
Third, current models of economic prosperity incorrectly and unhelpfully presume constantly increasing levels of consumption. Consumption drives production and production generates wealth and income. Japan, the US, and other economically developed nations face economic challenges because their stable or declining populations are not increasing total consumption and thus appear unable to sustain their current prosperity and to meet their financial commitments (pay government debt and promised old age pensions, for example). Furthermore, contrary to accepted economic theory, demand appears to diminish when prosperity passes some level (how many candy bars, coats, condominiums, or consultants does any one individual really desire?). People are now spending more time on mental pursuits (e.g., surfing the internet) that spark less innovation, require less productivity, and generate less consumption.
Fourth, less developed nations in contrast to developed nations have huge unsatisfied demand for economic goods and services. However, producing the good and services to satisfy that demand inexorably places new requirements on earth's resources, as the dense smog in China's major cities demonstrates. Even taking full advantage of every possible technology and resource (including solar power), the earth clearly seems unable to support all of its residents enjoying a Western standard of living. Lovelock persuasively argues in The Revenge of Gaia that exceeding the earth's carrying capacity will launch the planet into a self-destructive spiral from which recovery is impossible.
Fifth, I do not have a crystal ball with which to foretell the future. Indeed, the many Christians who read the Bible to discover the future and God's timetable for the events that they believe scripture predicts foolishly engage in eisegesis, i.e., knowingly misinterpreting scripture. Even if one accepts the Bible as the source of revealed propositional truth (which I do not), Scripture repeatedly emphasizes that no one knows God's timetable or plans. Similarly, I do not claim to know if humans will exhaust earth's carrying capacity by 2050, 2100, 2500, or some later date. Yet, I know that the earth does have a finite carrying capacity, that humans are rapidly depleting earth's finite resources, and that our economic models and systems all rest upon the twin false premises that both population and consumption can (and should!) grow without limit. Illustratively, even if solar energy were to power ALL transportation, the amount of food that people can grow on the earth has an upper limit. Sadly, the injunction to multiply and fill the earth, found near the end of the biblical narrative about Noah's ark, may be the only biblical injunction that humans can claim to have obeyed enthusiastically and completely. In short, we need to make changes now, while we may still have the opportunity to sufficiently alter course.