Limits to Growth: Overshoot

Limits to Growth by Donella Meadows, Jorgen Randers and Dennis Meadows. Here is a systemic analysis of the challenges we face in the 21st century.

Preface
The project that produced Limits to Growth took place in the System Dynamics Group of the Sloan School of Management within the Massachusetts Institute of Technology (MIT) from 1970 to 1972. Our project team used system dynamics theory and computer modeling to analyze the long-term causes and consequences of growth in the world’s population and material economy. We addressed questions such as: Are current policies leading to a sustainable future or to a collapse? What can be done to create a human economy that provides sufficiently for all?

A major foundation of our project was the “World3” computer model, which we constructed to help us integrate data and theories related to growth. With the model we can produce scenarios of world development that are internally consistent.

1972: The Limits to Growth reported that global ecological constraints (related to resource use and emissions) would have significant influence on global developments in the twenty-first century. The end of growth, in whatever form, seemed to us to be a very distant prospect in 1972. All World3 scenarios in LTG showed growth in population and economy continuing well past the year 2000. Even in the most pessimistic LTG scenario the material standard of living kept increasing all the way to 2015.

1992: Beyond the Limits is a 20 year update of our original study. Already in the early 1990s there was growing evidence that humanity was moving further into unsustainable territory. For example, it was reported that the rain forests were being cut at unsustainable rates; there was speculation that grain production could no longer keep up with population growth; some thought that the climate was warming; and there was concern about the recent appearance of a stratospheric ozone hole.

The past 30 years have produced many positive developments. In response to an ever growing human footprint, the world has implemented new technologies, consumers have altered their buying habits, new institutions have been created, and multinational agreements have been crafted. In some regions food, energy, and industrial production have grown at rates far exceeding population growth. In those regions most people have become wealthier. Population growth rates have declined in response to increased income levels. Awareness of environmental issues is much higher today than in 1970. There are ministries of environmental affairs in most countries, and environmental education is commonplace. Most pollution has been eliminated from the smoke stacks and outflow pipes of factories in the rich world, and leading firms are pushing successfully for ever higher eco-efficiency.

The past decade (this update was written in 2004) has produced much data that support our suggestion in BTL that the world is in overshoot mode. It now appears that the global per capita grain production peaked in the mid-1980s. The prospects for significant growth in the harvest of marine fish are gone. The costs of natural disasters are increasing, and there is growing intensity, even conflict, in efforts to allocate fresh water resources and fossil fuels among competing demands. The United States and other major nations continue to increase their greenhouse gas emissions even though scientific consensus and meteorological data both suggest that the global climate is being altered by human activity. Fifty-four nations, with 12 percent of the world population, experienced declines in per capita GDP for more than a decade during the period from 1990 to 2001.

The past decade also provided new vocabulary and new quantitative measures for discussing overshoot. For example, Mathis Wackernagel and his colleagues measure the ecological footprint of humanity and compared it to the “carrying capacity” of the planet. They defined the ecological footprint as the land area that would be required to provide the resources (grain, feed, wood, fish, and urban land) and absorb the emissions (carbon dioxide) of global society. When compared with the available land, Wackernagel concluded that human resource use is currently some 20 percent above the global carrying capacity. Measured this way humanity was last at sustainable levels in the 1980s. Now it has overshot by some 20 percent.

The global challenge can be simply stated: To reach sustainability, humanity must increase the consumption levels of the world’s poor, while at the same time reducing humanity’s total ecological footprint. There must be technological advance, and personal change, and longer planning horizons. There must be greater respect, caring and sharing across political boundaries. This will take decades to achieve even under the best of circumstances. No modern political party has garnered broad support for such a program, certainly not among the rich and powerful, who could make room for growth among the poor by reducing their own footprints. Meanwhile, the global footprint gets larger day by day.

We are not trying to predict the future. We see our research as an effort to identify different possible futures. We are sketching alternative scenarios for humanity as we move toward 2100.

The concept of global ecological constraints is not absurd. There truly are limits to physical growth, and they have an enormous influence on the success of policies we choose to pursue our goals. And history does suggest that society has limited capacity for responding to those limits with wise, farsighted, and altruistic measures that disadvantage important players in the short term.

Resource and emission constraints have created many crises since 1972, exciting the media, attracting public attention, arousing politicians. The decline in oil production within important nations, the thinning of stratospheric ozone, the mounting global temperature, the widespread persistence of hunger, the escalating debate over the location of disposal sites for toxic wastes, falling groundwater levels, disappearing species, and receding forests are just a few of the problems that have engendered major studies, international meetings, and global agreements. All of them illustrate and are consistent with our basic conclusion—that physical growth constraints are an important aspect of the global policy arena in the twenty-first century.

Our most important statements about the likelihood of collapse do not come from blind faith in the curves generated by World3. They result simply from understanding the dynamic patterns of behavior that are produced by three obvious, persistent, and common features of the global system: erodible limits, incessant pursuit of growth, and delays in society’s responses to approaching limits. Any system dominated by these features is prone to overshoot and collapse.

Overshoot
To overshoot means to go too far, to go beyond limits accidentally­—without intention. People experience overshoots every day. If you turn on the hot-water faucet too far in the shower, you may be scalded. At a party you may drink much more alcohol than your body can safely metabolize; in the morning you will have ferocious headache. Construction companies periodically build more condominiums than are demanded, forcing them to sell units below cost and confront the possibility of bankruptcy. Too many fishing boats are often constructed. Then fishing fleets grow so large that they catch far more than the sustainable harvest. This depletes the fish population and forces ships to remain in harbor.

The three causes of overshoot are always the same, at any scale from personal to planetary. First, there is growth, acceleration, rapid change. Second there is some form of limit or barrier, beyond which the moving system may not safely go. Third, there is a delay or mistake in the perceptions and the responses that strive to keep the system within its limits. These three are necessary and sufficient to produce an overshoot.

Overshoot is common, and it exists in almost infinite forms. The change may be physical—growth in the use of petroleum. It may be organizational—an increase in the number of people supervised. It may be psychological­—continuously rising goals for personal consumption. Or it may be manifest in financial, biological, political, or other forms.

The limits are similarly diverse—they may be imposed by a fixed amount of space; by limited time; by constraints inherent in physical, biological, political, psychological, or other features of a system.

The delays, too, arise in many ways. They may result from inattention, faulty data, delayed information, slow reflexes, a cumbersome or quarreling bureaucracy, a false theory about how the system responds, or from momentum that prevents the system from being stopped quickly despite the best efforts to halt it.

Throughout this text we will grapple with the difficulties of understanding and describing the causes and consequences of a population and economy that have grown past the support capacities of the earth.

Overshoot can lead to two different outcomes: Crash or Correction, a deliberate turnaround, a careful managed easing down. We believe a correction is possible and that it could lead to a desirable, sustainable, sufficient future for all the world’s peoples. We also believe that if a profound correction is not made soon, a crash of some sort is certain. And it will occur within the lifetimes of many who are alive today.

We have approached these issues in four ways—in effect using four different lenses to focus on data in different ways, just as the lenses of a microscope and a telescope five different perspectives. Three of these viewing devices are widely used and easy to describe (1) standard scientific and economic theories about the global system; (2) data on the world’s resources and environment; and (3) a computer model to help us integrate that information and project its implications.

Our fourth device is our ‘worldview’, an internally consistent set of beliefs, attitudes and values—a paradigm, a fundamental way of looking at reality. Everybody has a worldview; it influences where they look and what they see. It functions as a filter. When people look out through a filter, such as a pane of colored glass, they usually see through it, rather than seeing it—and so , too, with worldviews.

We cannot avoid being influenced by our own worldview. But we can do our best to describe its essential features to our readers. Our worldview was formed by the Western industrial societies in which we grew up, by our scientific and economic training, and by lessons from traveling and working in many parts of the wold. But the most important part of our worldview, the part that is least commonly shared, is our systems perspective.

Our training concentrated on dynamic systems—on sets of interconnected material and immaterial elements that change over time. Our training taught us to see the world as a set of unfolding behavior patterns, such as growth, decline, oscillation, overshoot. It has taught us to focus not so much on single pieces of a system as on connections. We see the many elements of demography, economy, and the environment as one planetary system, with innumerable interactions. We see stocks and flows and feedbacks and thresholds in the interconnections, all of which influence the way the system will behave in the future and influence the actions we might take to change its behavior.

Overview of the book Limits to Growth
The structure of this book follows the logic of our global systems analysis. We have already made the basic point. Overshoot comes from the combination of (1) rapid change, (2) limits to that change, and (3) errors or delays in perceiving the limits and controlling the change. We will look at the global change, then at planetary limits, then at the processes through which human society learns about and responds to those limits.

We start in the next chapter with the phenomenon of change. Absolute, global rates of change are greater now than ever before in the history of our species. Such change is driven mainly by exponential growth in both population and the material economy. Growth has been the dominant behavior of the world socioeconomic system for more than 200 years. For example the growth rate of the human population, which is still surging upward despite dropping birth rates. Industrial output is growing, too, despite dips from oil price shocks, terrorism, epidemics, and other short-term influences. Industrial production has risen faster than population, resulting in an increase in the average material standard of living.

A consequence of growth in population and industry is change in many other features of the planetary system. For example, many pollution levels are growing. Graphs throughout this book illustrate growth in food production, urban populations, energy consumption, materials use, and many other physical manifestations of human activity on the planet. Not everything is growing at the same rate or in the same way. Some growth rates have come down, but they still produce significant annual increments in the underlying variable. Often a declining growth rate still produces a rising absolute increment, when a smaller percentage is multiplied by a much larger base.

After World War II, from 1950 to 1975, there was a massive rise in the consumption base of several key factors in the system. Human Population grew 160%; Registered vehicles grew 470%; Oil consumption 540%; Natural gas consumption 680%; Coal 230%; Electrical generation capacity 1040%; Corn production 260%; Wheat 250%; Rice 240%; Cotton 230%; Wood pulp 830%; Iron 350%; Steel 350%; Aluminum 800%. The base has remained the same since 1975 while the growth rate has dropped to 120%-220% on these activities. Over the past half century human beings have multiplied their own population, their own physical possessions, and the material and energy flows they utilize by factors of 2, 4, 10 or even more, and they are hoping for more growth.

Individuals support growth-oriented policies, because they believe growth will give them an ever increasing welfare. Governments seek growth as a remedy for just about every problem. In the rich world, growth is believed to be necessary for employment, upward mobility, and technical advance. In the poor world, growth seems to be the only way out of poverty. Government and corporate leaders do all they can to produce more and more growth.

For these reasons growth has come to be viewed as a cause for celebration. Just consider some synonyms for that word: development, progress, advance, gain, improvement, prosperity, success.

Those are psychological and institutional reasons for growth. There are also what systems people call structural reasons, built into the connections among the elements of the population-economy system.

Growth can solve some problems, but it creates others. That is because of limits, the subject of chapter 3. The Earth is finite. Growth of anything physical, including the human population and its cars and houses and factories, cannot continue forever. But the limits to growth are not limits to the number of people, cars, houses, or factories, at least not directly. They are limits to throughput­—to the continuous flows of energy and materials needed to keep people, cars, houses, and factories functioning. They are limits to the rate at which humanity can extract resources (crops, grass, wood, fish) and emit wastes (greenhouse gases, toxic substances) without exceeding the productive of absorptive capacities of the world.

The population and economy depend upon air, water, food, materials, and fossil fuels from the earth. They emit wastes and pollution back to the earth. Sources include mineral deposits, aquifers, and the stock of nutrients in soils’ among the sinks are the atmosphere, surface water bodies, and landfills. The physical limits to growth are limits to the ability of planetary sources to provide materials and energy and to the ability of planetary sinks to absorb the pollution and waste.

In chapter 3 we examine the status of the earth’s sources and sinks. The data we present there make two points. One point is bad news; the other is good.

The bad news is that many crucial sources are emptying or degrading, and many sinks are filling up or overflowing. The throughput flows presently generated by the human economy cannot be maintained at their current rates for very much longer. Some sources and sinks are sufficiently stressed that they are already beginning to limit growth by, for instance, raising costs, increasing pollution burdens, and elevating the mortality rate.

The good news is that current high rates of throughput are not necessary to support a decent standard of living for all the world’s people. The ecological footprint could be reduced by lowering population, altering consumption norms, or implementing more resource-efficient technologies. These changes are possible. Humanity has the knowledge necessary to maintain adequate levels of final goods and services while reducing greatly the burden on the planet. In theory there are many possible ways to bring the human ecological footprint back down below its limits.

But theory does not automatically become practice. The changes and choices that will bring down the footprint are not being made, at least not fast enough to reduce the growing burden on the sources and sinks. They are not being made because there is no immediate pressure to make them, and because they take a long time to implement. That is the subject of chapter 4. There we discuss the signals that warn human society about the symptoms of its overshoot. And we examine the speed with which people and institutions can respond.

In chapter 4 we turn to our computer model, World3. It permits us to assemble many data and theories, putting the whole picture—growth, limits, response delays—into an explicit and coherent whole. The result of those simulations is, in nearly every scenario, overshoot and collapse of the planet’s economy and population.

But not all scenarios show collapse. In chapter 5 we tell the best story we know about humanity’s ability to look ahead, sense a limit, and pull back before experiencing disaster. We describe the international response to the news in the 1980s of a deteriorating stratospheric ozone layer. The story is important for two reasons. First it provides a strong counterexample to the pervasive, cynical belief that people, governments, and corporations can never cooperate to solve global problems requiring foresight and self-discipline. Second, it illustrates concretely all three features required for overshoot: rapid growth, limits, and delayed response (in both science and politics).

In chapter 6 we use the computer for its primary purpose—not to predict what will result from current policies, but to ask what could happen if we make various changes. We build into the World3 model some hypotheses about human ingenuity. We concentrate on two mechanisms for problem solving—technology and markets—in which many people have placed great faith. Important features of those two remarkable human response capacities are already contained within World3, but in chapter 6 we strengthen them. We explore what would happen if the world society began to allocate its resources seriously to achieve pollution control, land preservation, human health, materials recycling, and much greater efficiency in the use of resources.

We discover from the resulting World3 scenarios that these measures help considerably. But by themselves are not enough. They fall short, because technology-market responses are themselves delayed and imperfect. They take time, they demand capital, they require materials and energy flows, and they can be overwhelmed by population and economic growth. Technical progress and market flexibility will be necessary to avoid collapse and bring the world to sustainability. They are necessary, but they are not enough. Something more is required. That is the subject of chapter 7.

In chapter 7 we use World3 to explore what would happen if the industrial world were to supplement cleverness with wisdom. We assume the world adopts and begins to act upon two definitions of enough, one having to do with material consumption, the other with family size. These changes, combined with the technical changes we assumed in chapter 6, make possible a sustainable simulated world population of about eight billion. Those eight billion people all achieve a level of well-being roughly equivalent to the lower-income nations of present-day Europe. Given reasonable assumptions about market efficiency and technical advance, the material and energy throughputs needed by that simulated world could be maintained by the planet indefinitely. We show in this chapter that overshoot can ease back down to sustainability.

Sustainability is a concept so foreign to our present growth-obsessed culture that we take some time in chapter 7 to define it and to outline what a sustainable world might be like—and what in need not be like. We see no reason why a sustainable world needs to leave anyone living in poverty. Quite the contrary, we think such a world would have to provide material security to all its people. We don’t think a sustainable society need be stagnant, boring, uniform, or rigid. It need not be, and probably could not be, centrally controlled or authoritarian. It could be a world that has the time, the resources and the will to correct its mistakes, to innovate, to preserve the fertility of its planetary ecosystems. Sustainability could focus on mindfully increasing the quality of life rather than on mindlessly expanding material consumption and the physical capital stock.

The global economy is already so far above sustainable levels that there is very little time left for the fantasy of an infinite globe. We know that adjustment will be a huge task. It will entail a revolution as profound as the agricultural and industrial revolutions. We appreciate the difficulty of finding solutions to problems such as poverty and employment, for which growth has been, so far, the world’s only widely accepted hope. But we also know that reliance on growth involves a false hope, because such growth cannot be sustained. Blind pursuit of physical growth in a finite world ultimately makes most problems worse; better solutions to our real problems are possible.