People in developed countries sometimes believe that world population growth could be stopped rather quickly, if only the couples in the developing world would reduce their fertility. This misconception, unfortunately, is by no means restricted to laymen. It is based on the believe that people in the Third World so far have not - or only moderately - reduced the number of children. The opposite is the case. As we have demonstrated in Chapter 1 there was already a massive decline of fertility in many developing countries since the middle of the 1970s. And the projections assume a further significant drop. In fact, a world population of 9.4 billion people by the middle of the next century is only possible, if fertility - on a worldwide average - declines to about 2.1 children per woman.
Figure C3_1 is an attempt to visualize this past and projected fertility transition on a global level. It presents the cumulated number of people that lived (or are projected to live) in countries below a certain average level of fertility in 1950, 1995 and 2025. In 1950 there where no countries that had a Total Fertility Rate of less than 2.1. But some 1.5 billion of the 2.5 billion world population lived in countries with a Total Fertility Rate of more than 4.7. As can be seen from the lower blue line in the chart, only about 500 million people lived in countries where the TFR was less than 2.7.
That had changed significantly by 1995 (see the violet line in figure C2_1). Now some 2.5 billion people lived in countries with a TFR of 2.1 or less. And - due to the rapid fertility decline in China - some 4.2 billion people lived in countries where the average number of children was 3.4 or less.
A world population of "only" 9.3 billion people by 2050 would require, that roughly 6 billion people would have to follow a "low fertility" regime - that is, the average TFR in their countries would have to be only 2.1 children per women or less.

To answer the question stated above we can conclude that billions of couples in the Third World have already a much lower fertility than their parents. All UN projections (even the high fertility variants) assume a further rapid decline of average fertility in the Third World. Only then will we observe the projected slow-down of population growth and a leveling off at about 10 billion people.

The race between population and food is one of the oldest themes of (demographic) research - and probably one of the most controversial. Since Malthus' essay, 200 years ago, numerous books and papers - both scientific and popular - have been written on the issue (see for instance: Malthus, 1798; Vogt, 1948; Osborn, 1948; Fremlin, 1964; Ehrlich, 1968; Daily / Ehrlich, 1992; Waggoner, 1994; Cohen, 1995). Just summarizing the main arguments of this debate would go far beyond the scope of this paper. Elsewhere I have published a more detailed analysis (Heilig, 1996). Here, I will only mention a few arguments and facts which are essential for understanding the problem.

Just consider the case of the two most populous nations on earth: India and China. They both have a long history of exceptionally severe famines, before the "Green Revolution" and economic reforms improved the food supply for most people in the 1980s and 1990s. Especially for India, where floods and monsoons frequently destroyed the harvests, historians have documented numerous famines of apocalyptic dimensions, such as the great famine of 1630-31 which affected all of India or the food crises between 1555 and 1596 in the northwestern part of the country (Braudel, 1990). Yet none of these disasters decimated India's population in the long run.

We can identify many obvious reasons for the great famines in history - natural catastrophes, such as hurricanes, floods, droughts, crop pests or volcano eruptions; or man-made conditions, such as civil wars, trade restrictions, political terror, or forced deportation of peasants as in Stalin's terror regime. But to my knowledge there is no clear evidence that any of these famines was caused by a population suddenly outgrowing the carrying capacity of their land. When the natural disaster was over and the economic or political constraints removed, the food situation usually normalized - and very often the population began to grow again.

A lot has been published on the ecological collapse of past civilizations (Lowe, 1985; Culbert, 1973; Diamond, 1994). It is, for instance, quite likely that chronic food shortages - triggered by a dry period around AD 800 - have contributed to the decline of the Maya civilization (Hodell / Curtis / Brenner, 1995; Sabloff, 1990, 1995). But that was certainly only one element in a multi-factorial process of socio-economic decline - they didn't just perish all of a sudden in a famine. If food constrains really have contributed to the collapse of the Maya culture, than it was not an absolute limitation of bio-physical resources which caused the decline, but an inability to adapt the technology and the economic, social and political organization to the environmental constraints. The correlation between paleoclimatic records and the decline of the Classic Maya civilization is not necessarily a causal explanation of the collapse. For instance, it does not expain why the Mayas moved from the most seriously drought-affected southern lowlands to the northern lowlands (to Chichen Itza, Uxmal, Kabah or Sayil) which are not very suitable for agriculture. Why did they not move to the highlands where agro-climatic conditions are much better? (see also: Pohl, 1990; Sharer, 1994)

A high variability in the supply of food was typical for all traditional agriculture - especially in tropical regions where climatic hazards are abundant. They lacked the technology and economic arrangements to stabilize the food supply that have been invented over the past few decades, such as satellite-based early warning systems, emergency food aid or a strategic international cereal reserve. These modern measures of food crisis intervention have saved the lives of hundreds of millions. But there is a second, even more important, improvement in modern agriculture, that gives hope for the future: the enormous increase in productivity that could be achieved through artificial fertilizers, pesticides, efficient methods of irrigation and high yield varieties of major food and feed crops. Modern agricultural technology and new methods of farm management, combined with free access to (international) markets, have boosted the production of food during the past few decades - not only in Northern America and Europe, but also in Asia and Latin America.

Figure C3_2

Table C3_2

Worldwide, the average per capita food calorie supply increased from 2274 to 2709 calories per person per day between the three-year interval of 1961/63 and 1992/94. We eat more fat, vitamins and better and more protein than thirty years ago (see Table C3_2). The average per capita protein supply increased from 62.6 to 71.6 g per person per day. In Asia the increase was most spectacular: the average calorie supply grew from 1865 to 2577 calories per person per day; the average protein supply increased from 47.2 to 63.9 g per person per day. In the "Least Developed Countries" (which include some 50 poor developing countries) the average food situation, unfortunately, improved only marginally from 2012 calories per person in 1961/93 to 2032 calories per capita in 1992/94. This worldwide increase in food supply has certainly contributed to the fact that life expectancy has increased almost everywhere. The infant mortality of now is a small fraction of what it was when the world population was only half as large as today.

Table C3_3

This chronic undernutrition is a tragedy, but it is overwhelmingly not caused by bio-physical limitations of agriculture, but by economic, social and political deficiencies in certain countries, such as extreme poverty or inefficient and unfair systems of food distribution. For instance, it is not the soil conditions or the climate or population growth which have caused the near collapse of agriculture in Russia and the Ukraine in the early 1990s. Corruption, bureaucratic inefficiency, and the rigidity of a centralized command agriculture were the core problems of Russia's deficient food supply. Poverty plays a major role in India's food problems. While the country has experienced rapid economic development with a major increase in living standards among a growing (urban) middle class, a large section of the rural population still lives in absolute poverty. The scandal of undernutrition in the face of abundance in India is the inability or unwillingness of the ruling classes (and casts) to share some of their wealth with the poor. However, nowhere is the link between undernutrition and policy failure more obvious than in Africa. Civil war, corruption, economic mismanagement, the lack of agricultural infrastructure investment, failure to promote agricultural training, or radical economic experiments have played major roles in all recent African food crises.

In its landmark study on world agricultural prospects towards 2010 the FAO has concluded that "there appear to be no insurmountable resources and technology constraints at the global level that would stand in the way of increasing world food supplies by as much as required by the growth of effective demand. And, on balance, there is scope for such growth in production to be achieved while taking measures to shift agriculture on to a more sustainable production path."(Alexandratos, 1995)

Those, who entertain the public with "doomsday scenarios" of looming global food or health crises often argue that small population separated by undisturbed natural environment would be more healthy and "sustainable" (whatever that means). So let's go back in history to the "golden ages", when the world was an almost empty place. From paleo-demographic research we know that for most of human history the world population consisted of small tribes - each of a few dozen people - isolated from each other through vast areas of natural land. However, these ancient people lived short lives - often on the brink of starvation. Their remains frequently show signs of multiple chronically diseases, poor nutritional status and injuries related to violent conflicts. Most of their children died in the first few years. If they survived childhood they rarely became older than 35 years. We know of several (ancient) civilizations that vanished from earth despite (or maybe because) they lived thinly scattered over vast areas of almost natural, undisturbed land.

Even in more recent history the mighty Greek or Roman empires only had a tiny population as compared with today's populous countries in Asia or Africa. During the time of the "Peloponnesian War" in the middle of the 5th century B.C. (it was the peak period of ancient Greece) the city of Athens had a total population of just 133 to 173 thousand (Ploetz, 1986, 129). In the eleventh century Europe's large cities typically had less than 10,000 inhabitants - but even places with more than 500 inhabitants were considered a town. The city of Rome, "center of the world" for hundreds of years, never had a population of more than 200,000 people before the 18th century. Compared to the mega-cities of today with 10, 20 or even 30 million inhabitants these historical settlements were idyllic places. Yet, their population incredibly suffered from poor sanitation, lethal epidemics and frequent devastation due to war or fire.

At the beginning of the 14th century European populations typically were smaller than that of average Asian cities today. Most people lived in small rural settlements which were separated by huge areas of virgin land. It was estimated that in 1340 Italy's population was about 10 million; the British islands had a population of only some 5 million; France and the Netherlands had a total population of 19 million and Germany some 11.5 million (Ploetz, 1986). Living in an almost undisturbed natural environment this small and dispersed populations, however, suffered the greatest public health crises in recorded history: the bubonic plague. Within a century one third (or more) of the European population was killed. By the middle of the 15th century Italy's population had declined by 2.5 million (25%); on the British islands the population decline was in the order of 2 million (40%); the population in France and the Netherlands shrank by 7 million (or 37%); and Germany's population fell by 4 million (35%). But even this massive epidemic did not stop Europe's population growth in the long run. Only a century later the population had recovered.

Some people have argued that increasing population density will trigger a process of social erosion and disintegration. Experiments with rats and other animals have shown that stress related to population density can affect the social structure and individual health of the animals. However, this cultural and social doomsday scenario is by no means more likely than the dire food crisis predictions. There are few urban places in the world where crime rates are lower and average (healthy) life expectancy is higher than - for instance - in the extremely densely populated urban agglomerate of Tokio-Yokohama, Japan. Even the densely populated "urban jungle" of New York or Washington is a rather healthy and kind environment for people - if compared to the sparsely populated villages of Zaire, Sudan or the Ukraine (to select just three of the many rural crises regions). Recently, New York City has demonstrated that it is possible to lower crime rates even in places of extreme concentration of population and social problems. One might argue that it is unfair to compare highly developed urban areas with villages in poor countries. But it is easy to find other examples: China's very poor rural population has one of the highest densities in the world - yet their life expectancy is higher, their infant mortality is lower, and their nutritional and health status better than in most parts of sparsely populated Africa, Latin America or Russia. High population density as such has little influence on human well being. And it is certainly not a limiting factor of further population growth.

Of course, we have serious public health crises or events of social disintegration in certain countries or regions which have even increased national mortality rates, such as in certain African countries or Russia (Shkolnikov / Mesle / Vallin, 1996; Ryan, 1995). But they are man-made. They are caused by inadequate political, social and economic structures, which could be (and have been in other countries) changed by a competent political administration and /or by individual behavioral change. Human populations do not act like rats in cage. Other than these rodents they can intentionally modify their social conditions and individual behavior in order to adapt to a more densely populated world. This socio-economic adaptability to population growth is frequently ignored in Global Change research which is focused on the bio-geophysical aspects.

In my view, the successful adaptation of billions of people worldwide to an urban-industrial environment is one of the most interesting characteristics of global change.Only a few generations ago the majority of the world population lived from agriculture and settled in small villages and towns - usually under quite harsh conditions with high (infant) mortality and fertility, frequent famines and poverty. Today a large section of the (much larger) world population has not only changed (and improved) its mode of sustenance, but also adapted to the living environment of urban-industrial complexes with multi-million inhabitants and unprecedented population density. Many of us (including the author) might not like living in crowded cities - but we cannot ignore the fact that the concentration of people into an urban-industrial world was a highly successful organizational innovation in human evolution. In fact, with a projected 10 billion people on the globe we will be able to reserve some space for nature only, if the human population can be concentrated in compact, high-density urban agglomerates.

While there is no evidence that traditional health crises are able to limit world population growth new types of diseases might be more devastating. The obvious example is AIDS. For demographers dealing with population projections this is one of the most interesting questions and many studies have investigated the problem (see for instance: Bongaarts, 1996; US Bureau of the Census, 1996). Of course, no one can be sure about the future spread of HIV, but from our current knowledge it seems to be unlikely that the AIDS epidemic will have a significant effect on world population growth. The reasons are the following:

First, there is not one large uniform HIV epidemic spreading across the world population, but many distinct epidemics. Each one has its own origin, its specific transmission patterns and social background. Each one involves a certain risk behavior and is open to different types of prevention measures. Homosexual men, drug addicts, sharing injection needles, prostitutes and their clients, and heterosexual people who practice unprotected sex with multiple partners have a much higher probability of getting infected than those who avoid this practices. This is the reason while after more than 15 years of HIV spread in Europe still 76 percent of all AIDS cases diagnosed in 1996 were either homo/bi-sexual men or injecting drug users. Only 14% of the newly diagnosed AIDS cases were heterosexual men and women - many of these were partners of IV drug users. For instance, 31% of heterosexually infected female AIDS patients were partners of IV drug users (European Centre for the Epidemiological Monitoring of AIDS, 1996). In Europe, HIV so far has spread mainly among people with specific kinds of risky behavior that are not practiced by the great majority of the population. In fact, the available statistics indicate that in Europe - especially in Northern Europe - the AIDS incidence seems to have stabilized. The situation, obviously, is quite different in Africa, where a high prevalence of HIV infection is reported among the "general population". Several studies have demonstrated that HIV-related diseases are already the leading cause of death for young adults in many African cities (for instance in Abidjan). Rapid increases of HIV infections and AIDS cases were recently reported from India and Thailand. But these epidemics also seem to spread mainly among IV drug users, prostitutes and their customers and homosexual men with multiple, unprotected sex contacts. In any case, it is clear now that the AIDS disease is the result of a compartmented epidemic which is closely linked to behavioral and cultural patterns - not comparable, for instance, to the Black Death in the Middle Ages that swept more or less indiscriminately over Europe's population.

Second. While AIDS in Africa South of the Sahara has already increased infant and adult mortality rates by as much as 50% the impact on fertility is much smaller. A large percentage of HIV infected women will contract the virus only after they have already given birth to one or more children, because fertility is still very high and the average childbearing age is very low. And even after having been infected with the AIDS virus pregnancies are likely - due to the 8 to 10 year asymptomatic incubation period of HIV. Some 30% of these babies born by HIV infected mothers will not carry the virus (in Europe and Northern America mother-to-child transmission does not occur in about 50 to 60 percent of the pregnancies of HIV infected mothers). In Africa AIDS typically kills people in their early 30s - an age where much of the reproductive period is already completed. AIDS is undoubtedly a major public health crisis in Africa South of the Sahara - but its demographic effects are restricted to the increase of adult and infant mortality rates. Population growth rates will not be affected much due to the still high level of fertility and the massive demographic momentum built into the young age structure of African populations.

Third. The situation in Asia is unclear. Despite much higher HIV prevalence rates in Africa AIDS could potentially have a greater impact on population growth in Asia due to the much lower initial fertility. On the other hand it seems unlikely that all of Asia would be affected in a similar way. China, for instance, has so far reported very few AIDS cases.

In conclusion, we can assume for the moment that AIDS has no great overall demographic effect in Europe and Northern America. It increases mortality patterns in certain geographical regions and age groups, but not to such an extend that it would affect overall population growth. Despite very high rates of HIV prevalence and increasing mortality AIDS will probably only moderately slow down Africa's population growth. And in Asia - so far - many countries show no sign of rapidly spreading HIV infections.