It’s my pleasure to welcome Dr. Russ Hopfenberg to GIM. During the preceding weeks we’ve summarized and had the chance to discuss his work on the links between food supply, carrying capacity, and population growth, and to comment and ask questions. In this post, Russ generously responds to our questions and comments. Feel free to post additional comments and questions below, and Russ will return later in the month (update: make that next month) for one more round of follow-up comments (Update: here is the link to those comments). Thanks so much, Russ!

— John

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By Russell Hopfenberg:

I’d like to extend my thanks to John Feeney and Steve Salmony for inviting me to participate in this forum. I’d also like to express my appreciation to them for hand-holding me through the blogging process.

Question 1. The observation that individual countries’ food supplies don’t seem to correlate with their fertility rates as described by your hypothesis: I’ve read that one criticism of your work involves the observation that the countries with the lowest fertility rates tend to be the developed countries, and those with the highest tend to be those more deprived of food. (which would seem to contradict your hypothesis that more food means more population growth).

Response 1 – This is a very important question. It speaks to the complexity of understanding our global population difficulties. It seems that, in order to fully address the food-population issue, your question requires a thorough answer.

First, there is a biological fantasy imbedded in this question. The end of the question states “those with the highest (fertility rates) tend to be those more deprived of food.” I don’t think that this is biologically or physically possible as people are made from nothing but food. This kind of statement reveals the deeply held cultural position that humans are not subject to the same biological laws as the rest of the living community. I don’t think the questioner would ever make such a statement about another species’ population. If news came out that armadillos at the zoo had an elevated birth rate and now thousands were starving, I think the questioner would understand without hesitation that food supplies had first been elevated and then cut off. If the armadillo fertility rate continued to remain high, the questioner would understand that more food was being supplied.

Regarding humans, how is it possible that more people can be produced with less food? In reality, we have all seen the images of the UN workers handing out food. We have all seen the Sally Struthers commercials. When the crisis is over, i.e., the famine or political turmoil at least temporarily abates, there is more food available to the population in these areas. This increase in food availability precipitates an (unsustainable) increase in the population. The cycle then begins anew – another crisis, and more food is shipped in.

Second, it is true that more developed areas / countries show a lower birth rate.

This has to do with a phenomenon known as the demographic transition (DT). As you would find in a basic ecology book, it proceeds as follows: There are four stages in the classic DT model. In Stage 1, both birth rates and death rates are equivalent and high. In Stage 2, Death rates dramatically decline, but birth rates remain high. In Stage 3, birth rates begin to decline. And in Stage 4, both birth and death rates are equivalent and low. In other words, the declining birth rate occurs in countries that have traversed the DT.

But the DT model, as it is generally understood, is limited in historical and geographical scope. First, to even be in Stage 1, food production must already be at such a high level that birth rate and population size are greatly elevated. With this large population, environmental, medical and sanitation problems increase the death rate, so that it now matches the birth rate. Once health care and sanitation improve, the population enters Stage 2. In Stage 2, the birth rate remains elevated and the death rate decreases so the population naturally increases. As average resource consumption per individual increases, the population enters Stage 3. In Stage three of the demographic transition model, the birth rate declines. As this trend continues, the population theoretically moves to Stage 4. In Stage 4, birth and death rates are low but population and resource consumption are highly elevated.

Let me take a moment to summarize Abernethy and Moses & Brown’s position on the demographic transition: In stage 1 & 2, perceptions of increasing resource availability encourage and permit high fertility rates (Abernethy, 1997). This is followed, in stages 3 & 4, by a trend of declining fertility as societal expectations for high per capita resource consumption become established and tradeoffs between the number of children and resource allocation per person, are accepted (Moses & Brown, 2003).

I think the above paragraph needs a little more explanation. First, it is the worldwide perception that resource availability will be increasing. We have national and international farming programs, farms, agricultural departments, bureaus, and institutions that have a mission to increase food production and distribution. So, the perception is that resource availability will be increasing. Therefore, fertility increases. As the population grows, and resources are further increased, with the perception that they will be increasing further, fertility begins to decline but resource use per person increases. At the end of the road, with a greatly increased carrying capacity, large population size, low fertility rates and excessive resource use, the Brundtland Report, commissioned by the United Nations, estimated that it would take more than ten planet earths to supply the required resources for the now larger, more resource-consuming population. In other words, imagine if the entire planet’s population was similar to the US in resource use and fertility.

Question 2. The question of correlation versus causation (and why no correlation coefficient?).

Response 2 – My studies are certainly correlational studies. Imagine what an ethics board would say to a proposed human food-population experiment. Much that we know about humans comes from correlational studies. Think about the cigarette smoking and lung cancer link. Until recently, the tobacco industry’s defense was that all of the scientific evidence was from lab animal, human tissue, and human correlational studies. There was (and is) no human experimental evidence that links cigarette smoking to cancer. I offer the same type of evidence – animal experimental evidence and human correlational data. Regarding the correlation coefficient, I felt that the graph was sufficient. Also, the correlation coefficient might confuse matters as the correlation would be between the actual population data set and a theoretically derived population data set.

Question 3. If population growth is a function solely of food supply, one might realistically have to expect to see a future development of a further eroding of the ecosystems of this planet. ‑ Rampant overfishing, industrial farming, deforestation, etc., all because of a growing population’s rising demand for food.

Response 3 – Your assessment is true. If we continue on as we have been, then we will destroy the earth’s capacity to sustain us. However, the “biological fantasy,” imbedded in this question, rears its head once again. Our growing population’s “rising demand for food” is due to a misconception. Remember, population is a function of food supply, not the other way around. Food supply is an ecological magnet that draws population numbers to it.

Question 4. That seems an incredible leap. Family planning, education, free contraceptives, and empowering women are methods that has been shown to be effective.

Response 4 – I would like to ask the questioner – “Where have these things been shown to be effective?” They may help some individuals, in some places and for a little while, but I think the global population is still growing at a near exponential rate. To quote Daniel Quinn, “Birth control always works in fantasy. Where it doesn’t work, unfortunately, is in reality. For individuals, it works wonderfully well for limiting family size. What it won’t do is end our population explosion.”

Birth control has been around since at least 1960. Since then the global population has more than doubled. Also, for every person that chooses to have one child, resources are then available for someone else to choose to have more children. In theory, it could work that individuals choose to have fewer children even though there is an abundance of food available, it just isn’t very likely. And history bears out that, as a global population, given increasing agricultural production, we choose to increase our numbers. Also, we must understand that it is evolutionarily unstable for a population to diminish in a time of abundance.

Question 5. Would stopping the increase in food production cause more people to starve?

Response 5 – First, what we know is that as food production numbers have risen, the number of starving people has also risen, almost lock-step.

Second, if 3 billion tons of food (arbitrary number) was enough to feed the current world population last month, I can’t see why any more people would be starving if there were 3 billion tons available this month. … or next month.

Question 6. If we put a cap on global food production, how soon would world population growth stop?

Response 6 – I haven’t done the math on this, but I think we currently produce enough food worldwide to support a population of about 20 billion. Of course, it’s unclear as to how long the biological community can support the current human population. Let’s remember, right now there are over 200 species per day becoming extinct as a direct result of human activity. If we don’t understand the issues and act responsibly, at some point one of those 200 species will be our own. I think that the first order of business is to understand the cause and effect relationship between food availability and human population growth. Only then can thoughtful and effective action be taken.

Question 7. But how would stopping the growth of food production interact with the social and economic issues known/thought to influence fertility rates?

Response 7 – To quote Mark Meritt (2001),

Basic population ecology models will show that population growth is simply an epiphenomenon of a particular kind of economic growth, the increase of our food supply. Ecologically speaking, population growth is thus not a sustainability problem in and of itself but only inasmuch as it is caused by, and exacerbates, increasing resource use. Theories of organization and state formation, however, show that a growing population generates hierarchy within a social structure. Population growth can therefore systematically generate inequality by increasing the complexity of social structure, perpetuating poverty, material and otherwise, even in conditions of abundance. Further, the complication process itself is systematically unsustainable in its own way…. In the end, economic growth is, in more than a metaphoric sense, the largest pyramid scheme possible.

In other words, underlying our social and economic, as well as our population issues, is food supply. Social and economic issues influence the ways that the population grows (see the response to question 1) but the ultimate causative variable is food supply.

Question 8. Over some period of history, it seems we’ve tried to “keep up” with population growth by producing more and more food. I believe your contention is that we can’t “keep up” with population growth that way. The result is just more people, and ultimately more starving people. This leads to this question: Historically, did this attempt to “keep up” with population in our food production begin around the time of industrialized agriculture?

Response 8 – The food race certainly began long before the industrial revolution. Many ancient military campaigns were driven by the quest for more resources, especially food, for the growing population. I think we’ve made the idea of the “food race” more explicit in relatively recent times. But civilizations’ answer to starvation and famine has always been to attempt to increase food production. Of course, intensive agricultural production actually precipitates famine.

In closing, I think it’s important to remember that there will never be an answer to end all questions or an argument to end all arguments. I hope that, if nothing else, I have facilitated some thought and advanced the paradigm that human population dynamics are subject to the same laws as the population dynamics of all other species. With this perspective, you will be in a better position to answer your own as well as others’ questions.

Thank you for taking the time to entertain my responses. I hope that my answers addressed the issues sufficiently.

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Image source: Simone Merli, posted on flickr under a Creative Commons Attribution-NonCommercial-NoDerivs 2.0 license





