On Growth

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28. Roger Revelle

Professor Roger Revelle has been director of the Center for Population Studies at Harvard University, Cambridge, Massachusetts, since 1964.
He was born in Seattle, Washington, in 1909. He studied oceanography at the University of California.

In a recent talk I had with Dr. Philip Handler, president of the National Academy of Science, in Washington, D.C., he stressed the population question as the most serious problem of the planet today.

I would say that the two most fundamental events of our time are the very rapid growth of the earth's population that started after World War II and the other equally remarkable event, the urbanization of the human population, the gathering together, the aggregation in cities. Whereas at the beginning of the twentieth century, seventy years ago, there were less than a quarter of the world's people in cities, by the end of our century this proportion will certainly increase to over fifty percent; maybe even as much as sixty percent of the earth's population will be living in cities and towns. These two related events are certainly the most remarkable change in the human condition that has occurred for a very long time.

Most natural scientists adopt the Malthusian view of population, i.e., that human beings will multiply in numbers, by an exponential increase, up to the limits set by the food supply or by some other natural resource. It is for this reason that they feel that the present rates of population growth are very disturbing.

The first thing we have to ask ourselves is what are the conceivable limits of the numbers of people that the earth could support? With our present technology and agriculture, let's say that the primary problem is food supply, although, of course, there are other problems too. If we look at the potential food supply alone, it's probably true that the earth could support close to thirty times the present population, in terms of

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food. It would be possible to feed that many people on a physiologically adequate but not very satisfying diet. What we mean by this is that supposing that each person requires in terms of primary plant food, food produced by plants, somewhere between 2,000 and 3,000 kilogram calories a day - that kind of food production is certainly foreseeable from the presently cultivatable, not necessarily cultivated but cultivatable land. The total amount of land that we now cultivate is about three and a half thousand million acres. This quantity of land can probably be expanded to eight thousand million acres. Not that it would be a good thing to do, but it is something that could be done.

Why is it not a good thing to do?

Because most of the land that isn't now cultivated would be difficult and expensive to cultivate.

It would need enormous investments.

That's right, quite large investments.

And insecticides and fertilizers. It would contaminate the earth even further.

Yes, that's right. And water, large quantities of water. With the present rate of population growth it would take something like a hundred and fifty years before we get up to thirty times the present population. The earth's population is now doubling about once every thirty years. At this rate the population would go up eight times in ninety years, sixteen times in a hundred and twenty years or thirty-two times in a hundred and fifty years. As far as we can see, this would be - with our present agricultural technology and methods of food production - about the limit the planet could support.

One can argue, and people do argue, that the technology of food production is improving. We won't have to depend upon agriculture for the indefinite future, provided we have enough energy. This brings us to the more fundamental problem. Is there enough energy available? The total amount of energy locked in fossil fuels is probably limited at presently foreseeable rates of energy utilization to at most a few hundred years. By fossil fuels I mean, coal, oil and natural gas. Oil shales and tar sands are another form of concentrated organic matter in sedimentary

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rocks. As long as we depend on this kind of energy source, the available energy will last only a few hundred years. Both from the standpoint of food supply and from the standpoint of energy from fossil fuels - organic matter in the rocks - one can see a very definite limit.

The other two things that people worry about are the supply of other kinds of natural resources such as iron, aluminum, copper, zinc, chromium, lead, helium and mercury, and pollution. If the most of the future people in the world live at a so-called standard of living comparable to that of Western Europe or the United States, the waste products of civilization would be so great that we would drown in our own filth.

When we use a kind of mechanistic or deterministic model, it can be demonstrated that if populations continue to grow with a doubling time of thirty to thirty-five years, eventually there will be a limit. Eventually the growth of population will be limited by food supply, or by energy, or by other natural resources, or by pollution. This is essentially the thesis of the people who wrote the report Limits to Growth, and of Professor Forrester, who developed the more fundamental model, World Dynamics.¹

It seems to me that one has to ask several very serious questions about this particular set of models of the earth. First, and I guess the most important question, is this: Is there any historical evidence - from what we know about human behavior - to believe that in fact Malthus was right, that the human population does keep on growing up to the limits of the food supply? The Malthusian ‘principle on population’ is a mechanistic notion. It says that human beings do not act in their own interest, that human beings are automata, that they don't have any freedom of action and that they are helpless in the face of their own biology and their own environment.

There is very little historical evidence that this is so. On the contrary, there is lots of evidence that in fact people do control their own fertility, control their own population growth, if they see a reason to do so. It is not very well understood just what are the forces or what are the conditions which cause them to do this. Nevertheless, the historical evidence is that they do it. To take the most recent piece of historical evidence, in many of the so-called developed countries, not all, but many, including most of the socialist countries of Eastern Europe, the Russian and Ukrainian part of the Soviet Union, northern Italy, the Scandinavian countries, the United States, and Japan, the birth rate has come down very fast over the last thirty to forty years. The birth rate in the United States now is probably just about at the replacement rate, which means

1 See conversation no. 34, bibliography.

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that each woman is having just enough children to reproduce herself. Putting this in American terms it means she will be having about 2.1 or 2.2 children. More than half of those are boys. (There are three to five percent more boys born than there are girls.) Very few children in the rich countries die before they grow up and become able to reproduce. About two percent of the children who are born die before the age of one, and less than another one percent before they are able to reproduce themselves. So, somewhere around 2.2 live births per woman is what the demographers call a net replacement rate of one. And this is just about the number of children that in fact women in the United States are now having. Take the present fertility rate and spread it over the reproductive lifetime of women in the United States, that's the way it would turn out. The birth rate has been dropping very fast for the last seven or eight years, both among the whites and among the Negroes in the United States.

I think it is not unlikely that in all the developed countries we will find within the next ten years that women are not having enough children to replace themselves. Why this is so is not understood, but there are several possible explanations. Perhaps the most general is that the psychic, economic and social benefits that children bring to people, to potential parents, are not as great as they used to be. In the United States, a hundred and seventy years ago, the average woman had seven children. The number of children per woman has been coming down throughout the last hundred and seventy years. It reached a low point in the 1930s and went up again with the baby boom in the 1950s, but now it's coming down again.

Many people will say that this is all very well, but most of the world's population doesn't live in the developed countries, the rich, affluent countries, but in poor countries. And in the poor countries the birth rates have not yet come down, whereas the death rates are just about as low in the poor countries as in the rich ones. What has caused the enormous growth of population in the Third World is the fact that the birth rates have not come down but death rates have. For example in India, in Pakistan, and in Bangladesh, the average life expectance in 1920 was between twenty and twenty-five years. That means that a baby at birth could look forward to an expectation of life of about twenty-two or twenty-three years. It does not mean that the average person who survived for just a few years of life only lived twenty-two or twenty-three years. About half of the children died before the age of ten.

Now the life expectancy in India, Bangladesh and Pakistan is about fifty years. It's even higher in South America. It's lower in Africa, but

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in the Third World as a whole there's been maybe an increase of two and a half times in life expectancy during the last fifty years. Little decline in birth rates has occurred during this period, and that's what has caused the so-called population explosions, the enormously rapid rate of population growth. The average woman in a developing country gives birth to four or five children, often six or seven children. These infants are surviving now, not all of them, but eighty percent of them survive beyond adolescence. In the developed world, the average woman has a little over two children, but nearly all children survive and grow up.

Venezuela has a population-growth rate of over three percent, and yet it has a high income. Also Brazil and Mexico. Their per capita incomes are going up quite rapidly, even though the population is also going up very fast. Is there an explanation?

The explanation probably is that a great many people in Brazil and Mexico are not sharing in the apparent prosperity of the country as a whole. These countries have what used to be called two-nation societies, societies in which the poor remain poor, while the rich get richer.

The gap grows wider -

- there is a modern sector in which people are getting rich and a traditional sector in which people are in some ways worse off than they were before. That seems to be true for Mexico and Brazil; it is certainly true for Venezuela.

Now there is another country, which is perhaps the most important of all from the standpoint of population, and that is China.

About one out of every four people on earth is a Chinese. Very little is known about this enormous country. They have had only one census in modern times. This was in 1953. We don't really know what the Chinese birth rate is, what the death rate is or how these rates have been changing. We don't even know how many people there are in China. It may be perhaps a hundred or two hundred million people more than we think. There aren't many statistics. The Chinese have never been very much interested in statistics. They neither gather them nor publish them. The best thing we can do with China is to have a sort of impressionistic view of it.

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The Limits to Growth study was meant as a contribution to study how to achieve equilibrium after an era of sheer unlimited expansion and growth.

Yes, there is no question about the fact that we have to arrive at a steady-state world. I mean, the world cannot possibly continue its exponential growth. The nature of exponential growth is that sooner or later things blow up. My principal criticism of the Limits to Growth is that the authors assume that exponential growth is bound to continue until a catastrophe stops it. It is not bound to continue at all. Exponential growth usually occurs only during a transition period. We are living now in one of the great transitions of human history. Toynbee has said that we live at the hinge of history. We are changing from one kind of world to another. The kind of world that has to exist in the future - not that ought to exist but has to exist - must be a more or less steady-state world.

The question is what kind of a steady-state world is it going to be? One possibility is a world with a population of around twelve billion people, ten to twelve billion people, with adequate food supply for all, resources adequate for all, a good life in material terms for everyone, and pollution under control. The extreme alternative to this is another kind of steady-state world in which we have somewhere between fifty and a hundred billion people, in which the death rate has risen to match the birth rate, in which most people never get enough to eat (which is the reason why the death rate would have risen to match the birth rate), in which poverty is almost a universal human condition, and the future is essentially hopeless, because we will have used up most of the natural resources. Mankind will live in a very limited way; most people will have just a bare existence under quite unpleasant conditions.

The real problem is what kind of a steady-state world do we aim for. But Limits to Growth says something worse than this: They say that the future course of events is a continuing rise and then a collapse, not a gradual approach to a steady-state, no matter how bad, but an overshooting of the use of resources, an overshooting of population, production and economic growth and then a rapid and catastrophic decline of production, population and available resources.

The argument hangs on the kind of model one builds. The model MIT built depends on continuation of exponential change. But first, exponential change cannot continue; and second, it need not continue. Instead of continuing exponential growth, one can equally well expect an S-shaped curve with growth slowing down as it approaches a limit. The

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economy and the population grow less and less rapidly rather than growing faster and faster, and then collapsing. We are now down here... going up like this... but eventually growth can slow down and taper off.

They tried to prove that a breaking point will occur unless we do something fast - unless we change the curves, change the trends.

Their main point is that unless we start doing something right now, we will end up with this collapse. What I would argue is that they put things in the wrong priority. In order to bring the birth rate down, in order to create the conditions in which people see their own interest in having smaller families, we need a continuation of economic development, particularly in the developing countries. In my opinion, it is essentially impossible, on the basis of experience to date, to expect people in these countries to behave in a way that will stabilize population, bring population to a stationary level, unless they have sufficient economic development so that they see some reason for doing so. It's a very easy solution on the part of us Westerners, on the part of the rich countries, to say to the people of the poor countries, you cannot possibly develop, because the resources are not available, because there would be too much pollution.

If people are going to limit their own fertility, and if we are all going to come to a point where we live in a stable, peaceful, relatively happy world, we must have more worldwide economic and social development. The question is: Are resources sufficient and can pollution be controlled? Is it possible to have economic growth without too much pollution? I think that we have to search a good deal deeper than the Limits to Growth people have looked.