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Population Growth, Sustainable Development, and the Environment

Sergey Kapitza
Population Action International, Washington, DC
(Current address: Institute for Physical Problems, Russian Academy of Sciences, 2 Kosygina St., Moscow 117334, Russia)

The long-term state of the biosphere—the conservation of species and of biodiversity—will depend to a great extent on the population growth of the world and the demographic pressure on the environment. At present, the population of the world is 5.9 billion, and it is growing by 1.5% a year; 250,000 inhabitants are added every day. Practically all population growth occurs in the developing world. At the same time, much of the industrial development also happens there. On the other hand, in the foreseeable future, because of transition in the population, global population is expected to level off at 12–14 billion. It is in these terms that one should consider the effect of humankind on the future of our planet, taking into account the trends in development seen in the larger context of the dynamics of the world-population system.

The links of population growth and development were the subject of a seminal statement of the Royal Society of London and the US National Academy of Sciences titled Population Growth, Resource Consumption, and a Sustainable World and signed by the presidents of the two societies (Atiyah and Press 1993). In that statement, probably for the first time, two great academies voiced their opinion on this all-important and sensitive subject. They came to the following conclusions:

The applications of science and technology to global problems are a key component of providing a decent standard of living for a majority of the human race. Science and technology have an especially important role to play in developing countries in helping them to manage their resources effectively and to participate fully in worldwide initiatives for common benefit. Capabilities in science

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and technology must be strengthened in LDCs [less-developed countries] as a matter of urgency through joint initiatives from the developed and developing worlds. But science and technology alone are not enough. Global policies are urgently needed to promote more rapid economic development throughout the world, more environmentally benign patterns of human activity, and more rapid stabilization of world population. The future of our planet is in the balance. Sustainable development can be achieved, but only if irreversible degradation of the environment can be halted in time. The next 30 years may be crucial.

The issues raised in that statement have grown in importance, and a major international debate has followed. The problem of global population growth has been reviewed thoroughly, and it is probably best summed up in the book The Future Population of the World: What Can We Assume Today?, edited by Lutz of the International Institute for Applied Systems Analysis, IIASA (Lutz 1994). An extensive study by Cohen (1995), How Many People Can the Earth Support?, reviews a vast amount of data and many ideas and misconceptions. Perhaps the complexity and difficulty of these subjects, which are essential to discussions of sustainable development, can be seen in the fact that the titles of both books are questions.

The book by Cohen and chapter 10 of the book by Lutz, “How Many People Can Be Fed on Earth?”, show that the idea of carrying capacity is counterproductive, if not misleading or even wrong. That point is well illustrated by the “limits” suggested by various writers since 1600, when fewer than a half-billion people lived. Until 1900, the limits indicated are rather similar and mostly reasonable, around 10–15 billion; these figures compare well with modern assessments. The huge discrepancies—from 1 billion to 1 trillion—seen in projections from the last 50–100 years more likely indicate the ups and downs of the subjective mood, private and public, that in its own way expresses the turbulent history and transitory nature of 20th century, rather than a trend toward a greater understanding of human destiny.

Projections of Population Growth by Demographic Methods

Those projections of the world's population were based on assumptions of the availability of resources, mainly land. Most modern estimates, however, are the result of extensive studies of population growth that look at population dynamics rather than resources. Results can be obtained with standard demographic methods and are valid for 1 or 1.5 generations. For periods of longer than about 30–50 years, demographic calculations become computationally unstable. All extrapolations farther into the future come from plausible hypotheses regarding the future development of humankind, which set guidelines for the calculations made. For the year 2100, the most probable projections by a team at IIASA indicate a population of 11.5 ± 1 billion. That estimate indicates that in the next 100 years, the population of our planet will barely double (Lutz and others 1994).

Of critical importance is that the future population of the world will be determined not by the incessant growth that has marked development until the present

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but by a complex transition to a stabilized world population. This demographic transition, as it has become known, is the crucial feature of modern human population growth. The phenomenon, first recognized by Notenstein in 1950, now is determining the lack of population growth in the developed countries; in the next 50 years, it undoubtedly will lead to a decrease in the rate of growth and the final leveling off of the world's population. For the more-distant future, demographers can make only plausible guesses, estimating a stabilized world population of some 12 billion.

The demographic transition will be accompanied by a marked change in the age structure of the population. Currently, people younger than 15 years make up 32% of the world population and people older than 65 years, 7%; after the transition, the numbers will be 18% and 22%, respectively. At the same time, a huge number of people will move to towns in a global pattern of urban development. Ultimately, the demographic transition will lead to major changes in the lifestyle and values of billions of people. It is certainly the most significant event in human history, seen on a large scale. That is why it is well worth the effort to study the demographic transition with methods other than those provided by modern demography.

Modeling the Growth of Humankind

I have developed an alternative approach (Kapitza 1994, 1996a,b), which interprets the global population as an interactive dynamic system. The entire population of the world is the object of study. The global-population system is considered to be an entity, coupled with interactions that determine its long-term growth and development, rather than as a mere sum of countries and regions, each following its own pattern of growth. This is the next step in generalizing population growth. In fact, when describing the demographics of China or India, we already are summing up, in a single measure of growth, a vast country that has many regions and cultures of great ethnic diversity and that encompasses 17–20% of all humanity.

In treating the whole of humankind in such a general way, it is also possible to expand the time scale considerably. One must break away from the unit of a generation that is used customarily in demography and even go beyond the millennia of history to the millions of years that provide the scale for human development as seen in anthropology. For shorter intervals, this way of describing the growth of human population must merge with and rely on the methods and concepts of demography. Thus, the two ways of describing our growth and development complement each other and provide mutual support and justification of their results.

If we consider the long-term pattern of the growth rate of the human population, we see that the rate is proportional to the square of the total number of people. This nonlinear growth corresponds to a hyperbolic growth curve and is well known for describing explosive systemic development. For humankind, quadratic growth is valid for more than 1 million years into the past, right from the appearance of Homo habilis, the primeval tool-maker. The quadratic law of growth

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is applicable only to the total number of people; it cannot be applied to describe regional growth. But every region and country participates in and is influenced by it because we are dealing with a nonlinear law that implies a global interaction in the complex population system of the entire world.

However, the quadratic law leads to a divergence in a finite time. The divergence has begun already; if the growth rate thBat has been valid for so long persists, the runaway into infinity will happen in 2025. The pattern of quadratic growth can describe the first stage of the population transition—the population explosion. This is a new way of looking at the demographic transition as a phase transition, describing it in terms and methods that come from nonlinear physics of systems.

For explosive divergences, it is well known that a cutoff must be brought in, taking into account factors of less importance during the main period of growth. As we approach the singularity, the concepts of demography become significant. They indicate that if we take into account the finite human life span and reproductive time, we can expect the whole pattern of growth to change. The development of this phenomenon, following well-established methods of systems analysis and physics, envisages an asymptotic transition to a stabilized world population of 12–14 billion, with 12 billion reached in 2100. A time constant of 42 years, characterizing the human life span, has to be incorporated into the calculations.

This model has developed into a theory that describes the gross features of the growth of humankind. It provides an estimate of the beginning of human development, some 4–5 million years ago, and an estimate of the number of people who ever lived, of 100 billion. As we approach the critical year of 2007 (it shifts from 2025 when the 42-year cutoff is taken into account), the dynamics of growth indicate a logarithmic compression of the time scale of history. In 2007, the maximal annual growth of 85–90 million is expected, but the relative growth rate already reached its peak, 17% per year, in 1989.

My approach now reconciles well with the methods of demography and can be seen as complementary in treating the same problem on a larger scale: the way human population has led to the concept of the population imperative. This means that growth has not been limited globally by resources, but is governed by the inherent nature of the systemic interactive dynamics of the global population system. On a large scale, growth has been systemically stable, although local and temporal variations have occurred.

Factors that Limit Population Growth.

At this point, it is appropriate to mention the fundamental differences between my model and the Malthusian population principle. According to Malthus and those who developed the same ideas later into the “limits-to-growth” concept, growth is limited by resources (Meadows and others 1972). In the case of Malthus, the lack of food led to hunger, which decreased the birth rate. But this way of treating the origin of growth and the factors that control it does not consider that humankind is a highly interactive system. In the case of my model, the rise in the number of people, observed over the ages, is the outcome of all factors

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of a biological, technological, economic, social, and cultural nature relevant to growth in society and expressed by the quadratic-growth law. In other words, we must treat humankind as an entity, an open system, and integrate everything that is going on inside it. That is the meaning of systemic development, as opposed to the reductionist approach that is pursued in most global models, in which all relevant processes and resources are purportedly taken into account separately. With great expertise and effort, this is done in demography and is the reason for its limited temporal horizon in describing growth, although in this case we get insight into the details of growth and its distribution in age groups and space.

It should be noted that humans are not only qualitatively different but also quantitatively different from any mammals of comparable size and position in the food chain; humans are 100,000 times more numerous. Only domestic animals that accompany humans outnumber by far their relatives that live in comparative equilibrium in the wild. Humankind has broken away from the rest of nature and has developed a habitat of its own. On the other hand, in the last million years, humans have scarcely evolved biologically at all since the appearance of Homosapiens. These are the basic reasons for considering the development of humankind as a separate entity, a system of its own, in which, in the process of sapientation, social, technological, and economic development have determined our incessant growth.

In the global interaction of all people, the exchange of information and the transfer of knowledge are instrumental in how growth becomes the outcome of all processes in the complex nonlinear global system. The interaction described by the quadratic growth rate can be seen as a collective phenomenon, an expression of consciousness, peculiar to humans and making them fundamentally different from all other animals. By speech and language, information is transferred vertically from the past and into the future. At the same time, information is spread horizontally, synchronizing human development globally. The nonlinear systemic theory of the growth of humankind indicates the synchronous development of the large-scale features of history and prehistory that are well substantiated by observations of historians and anthropologists.

Finally, this theory indicates that our development over the vast period of growth can be seen best on a logarithmic scale. This has been intuitively done by anthropologists, who otherwise could not accommodate on a single chart the million years of the lower Paleolithic age with the 10,000 years of the Neolithic age. Calculations show that the time of the development of all humankind should be shown logarithmically, reckoning time from the year 2007—the peak of the demographic transition—so that the whole human story can be shown in the same table (see figure 1). A table like this also offers an explanation of the nonuniform way in which time has passed during the course of our development. This change in the relative duration of events is a direct kinematic result of the accelerated growth of humankind proportional to the population of the world. As we approach the singularity of the demographic transition, the transformation and compression of time in history are striking. In the theory of growth, the largescale features appear as epochs and periods of population growth. The first epoch, A, which lasted 2.8 million years, corresponds to the time it took for Homo

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Figure 1
The Development of Humankind on a Logarithmic Scale.

habilis to emerge during the evolution of early hominids. Epoch B, the time of quadratic growth, began 1.6 million years ago and culminated in 1965 in the advent of the demographic transition. This led to epoch C, the transition to a stabilized population of the world. The periods traditionally identified by anthropology and history subdivide epochs A and B into 12 intervals of DT years. These intervals become shorter and shorter as we approach 2007, the critical date of the transition.

This novel way of presenting human development is the result of a consistent and straightforward mathematical model for interpreting the general features of the development of humankind. It comes from applying methods of sciences that arrogantly call themselves exact to problems of the humanities—an effort that is far from easy, because the sides need to learn to understand each other but have

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long been separated in our culture. It seems that this can be done only through an interdisciplinary endeavor, and global problems likely are best suited for this purpose. Population growth now practically has reached the peak of the transition to a stabilized world population for the foreseeable future, and the period 1965–2050 is the time of this transition. The transition is remarkably short if we compare it with the million years of our development, but 10% of all the people who ever lived will experience this period of rapid change. The pace and width of the transition are the result of interactions in the global population and the outcome of the complex behavior of a highly nonlinear dynamic system. During this eventful period of 85 years, the population of the world will become 3 times larger and much older. It is the most critical and singular period ever to be experienced by humankind. All through the ages, humankind has followed a stable, persistent pattern of growth; this pattern is changing rapidly now to a stabilized global population. In fact, it cannot change faster (barring an all-out nuclear war or extraterrestrial intervention!), and it is this rapid change—from blowup to saturation—that must be kept in mind in any attempt to understand the global problems, that now face the world.

Sustainable Development

Since the Conference on Development and the Environment was held in Rio de Janeiro in 1992, the concept of sustainable development has emerged as an important landmark in the international debate on world affairs. In the summer of 1997, a review conference in New York showed the difficulties—even a split in the attitudes toward development and the environment—between the developed and developing nations. The consensus reached in Rio de Janeiro is being questioned now, and the origin of the differences in attitudes needs to be investigated, taking into account the population transition.

Because the transition first happened in the so-called developed world and now is proceeding to the developing world, it would be better to speak in terms of the countries where the population has already stabilized and the greater part of the world, which now is passing through the demographic transition. To see the magnitude of these events, the population undergoing the transition now is 15 times larger than, and the rate of change is twice as great as, in the developed world. Today's annual growth rate in China is 1.1% in a population of 1.3 billion; in India, the annual growth rate is 1.9% in a population of 930 million. The respective economic growth rates of these countries are 12% and 6–7%. What should be of greatest concern for the world community is stability during this remarkable time of development (Kapitza 1996c). On the other hand, the differences in the stages of the demographic transition provide the demographic and economic backdrop against which the concept of sustainable development must be examined.

In the developed world, the demographic transition already has led to a stabilized and rapidly aging population of predominantly senior citizens. The process of urban development is slowing down. Indications of such a stable, affluent, and highly developed society can be seen in many ways. Extensive service sectors of

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the economy—of health, education, and social security—are developing. The change in values of the fundamental paradigm of development—from growth on all counts in terms of children, cars, or soldiers to that of limited growth and concern for the environment—is important. We, hopefully, can see a trend to abate consumption, making it a subject of public awareness. As an expression of a new consciousness, global responsibility for the environment is gaining ground. It is from these premises that the idea of sustainable development has sprung (Kapitza 1997).

The other side, that is, the developing world, has quite different circumstances. The younger generations are predominant. There is a vast migration from villages to towns, leading to rapid urbanization. The young migrants are the new working class, who are active and unsettled and who can man armies or leave the country or, in the case of unemployment, become a source of unrest. The possible scenarios are well known. In the developed world, we need to look back only 100 or 150 years to find a similar situation, but we must keep in mind that growth and everything that accompanies it occur twice as fast today as they did then.

In assessing changes and development in the world system, one also needs to think in terms not of averages, but of distributions—distributions by sex and age in populations, in wealth and income, in education and health, and in the very nonuniform distribution of people in towns and villages. Without studying the evolution of these distributions, it is practically impossible to describe the changes that are happening. Because of a lack of understanding of the statistical origins and social relevance of these distributions, ideas have evolved on drastic cuts in world population, of a “golden billion”, and of extrapolating the southern California lifesryle worldwide.

All distributions of land, food, energy, and wealth show that the world population system is far from equilibrium. The origin of these distributions is most important; it indicates rapid growth, which increases as a country approaches the demographic transition. On the other hand, the evolution of these distributions shows that, in processes of growth, the world population system was dynamically sustainable—otherwise it could not have evolved consistently for 1 million years as it has. In this context, Vishnevsky made an interesting observation in interpreting the dynamic model. He remarked that the history of humankind preceding the demographic transition can be seen as a rapid passage, a nonequilibrium, a transitory state of growth and self-organization toward a stabilized world population, which will be the long-term asymptotic and stable state of humankind. This point is important to remember when we are addressing global problems of the present age.

We must look into the meaning of sustainability in a world of zero or very low population growth. We should assume that the world population is moving rapidly toward stabilization and that, in promoting and propagating the idea of a sustainable world, this must be taken into account. But will we run out of global resources at the expected levels of consumption? That is what matters and what led to the split at the 1997 New York conference.

The point is often made that we are living in a common world and that we must consider the common heritage that we all share—be it the atmosphere, the

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oceans, or the complexity of the biosphere. That is certainly true, but where are the limits of demanding a common policy on these issues? In this new, stabilized world, the population by the end of the next century will be twice as large as it is today. The energy produced—the best way of estimating the use of resources—will be 4–6 times as large as it is now (Holden 1991). Can our planet carry this load without collapsing? Probably so, but great changes will take place. It is best to remember that the environment in every populated part of the world—from Europe to China, India, and much of North America—has a highly transformed natural habitat. There are still large sparsely populated spaces that escape our attention. A comparison of Argentina and India is instructive. India's area is about 40% larger than Argentina's, but its population is 30 times greater. India is one of the oldest civilizations, if not the oldest, whereas Argentina, as a nation, is only 200 years old. But Argentina reportedly could feed the entire world.

As long as such large discrepancies exist, it can be assumed that the global population system is open and has enough resources to support its development in the foreseeable future. The first indication of a global shortage will be a more uniform pattern of the use of resources. On this scale of events, the next century will be crucial for humankind to negotiate the last stage of adaptation to the stabilized state of its future, when, we hope, we can carry out a pattern of sustainable development. At that stage, all progress will need to be reckoned with by means that do not involve numerical growth, the stereotype of development that has dominated humankind for 1 million years and tens of thousands of generations. History and our present experience show that our “software”—our ideas and values—evolves much more slowly than our “hardware”, which for ages was geared for maximal growth and productivity. Under the pressure of rapid development, these long-entrenched attitudes will have to change. Of all factors, this probably is central to resolving the issue of sustainability.

Sustaining Biodiversity

These ideas provide the historical context for considering the sustainability of biodiversity. As recent environmental research has shown, we can expect to lose biodiversity mainly during the period of rapid growth, as happened in the developed world two or three generations ago, during the first stage of the demographic transition—the stage of rapid growth. Today, many see the very fast growth of the developing world as the primary menace to the global environment, with biodiversity in first place over the short term, compared with long-term environmental issues. The sheer rate of growth and the rapid transition to a stabilized new world are competing factors that will determine the outcome and the state of the world in the foreseeable future. What can and will resolve these issues to some extent is a change of values that will determine our patterns of social behavior. At the peak rate of the present stage of development, material growth by far outstrips the development of humankind's “software”.

The differences in our values, ideas, and material development are influenced to a great extent by the processes of globalization. If the spread of technology, money, and industrial know-how is accelerating development, the appropriate

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diffusion of ideas and values is lagging. The sheer complexity of global society is complicating matters, for it takes much time for our social habits and customs to be established and even longer for international institutions to evolve. The time scales involved can be traced to the fact that it takes only 9 months to produce a human's “hardware” but at least 20 years to program a human's “software”. These are the fundamental biological and human constants that finally determine both our personal development and the fate of humankind. Ultimately, it is the interplay and balance of matter and mind that will resolve our predicament.

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