By Donella Meadows, Jorgen Randers, and Dennis Meadows

The following piece is a short synopsis of Limits to Growth: The 30-Year Update. The full length book is available at Chelsea Green’s website.

A Synopsis: Limits to Growth: The 30-Year Update

The signs are everywhere around us: Sea level has risen 10–20 cm since 1900. Most non-polar glaciers are retreating, and the extent and thickness of Arctic sea ice is decreasing in summer.

In 1998 more than 45 percent of the globe’s people had to live on incomes averaging $2 a day or less. Meanwhile, the richest one- fifth of the world’s population has 85 percent of the global GNP. And the gap between rich and poor is widening.

In 2002, the Food and Agriculture Organization of the UN estimated that 75 percent of the world’s oceanic fisheries were fished at or beyond capacity. The North Atlantic cod fishery, fished sustainably for hundreds of years, has collapsed, and the species may have been pushed to biological extinction.

The first global assessment of soil loss, based on studies of hundreds of experts, found that 38 percent, or nearly 1.4 billion acres, of currently used agricultural land has been degraded.

Fifty-four nations experienced declines in per capita GDP for more than a decade during the period 1990–2001. These are symptoms of a world in overshoot, where we are drawing on the world’s resources faster than they can be restored, and we are releasing wastes and pollutants faster than the Earth can absorb them or render them harmless. They are leading us toward global environ- mental and economic collapse—but there may still be time to address these problems and soften their impact.

We’ve been warned before. More than 30 years ago, a book called The Limits to Growth created an international sensation. Commissioned by the Club of Rome, an international group of businessmen, states- men, and scientists, The Limits to Growth was compiled by a team of experts from the U.S. and several foreign countries. Using system dynamics theory and a computer model called “World3,” the book presented and analyzed 12 scenarios that showed different possible patterns—and environmental outcomes—of world development over two centuries from 1900 to 2100.

The World3 scenarios showed how population growth and natural resource use interacted to impose limits to industrial growth, a novel and even controversial idea at the time. In 1972, however, the world’s population and economy were still comfortably within the planet’s carrying capacity. The team found that there was still room to grow safely while we could examine longer-term options.

In 1992, this was no longer true. On the 20th anniversary of the publication of Limits to Growth, the team updated Limits in a book called Beyond the Limits. Already in the 1990s there was compelling evidence that humanity was moving deeper into unsustainable terri- tory. Beyond the Limits argued that in many areas we had “overshot” our limits, or expanded our demands on the planet’s resources and sinks beyond what could be sustained over time.1 The main challenge identified in Beyond the Limits was how to move the world back into sustainable territory.

1 To overshoot means to go too far, to grow so large so quickly that limits are exceeded. When an overshoot occurs, it induces stresses that begin to slow and stop growth. 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 try to keep the system within its limits. The delays can arise from inattention, faulty data, a false theory about how the system responds, deliberate efforts to mislead, or from momentum that prevents the system from being stopped quickly.

The 30-Year Update

Now in a new study, Limits to Growth: The 30-Year Update, the authors have produced a comprehensive update to the original Limits, in which they conclude that humanity is dangerously in a state of overshoot.

While the past 30 years has shown some progress, including new technologies, new institutions, and a new awareness of environmental problems, the authors are far more pessimistic than they were in 1972. Humanity has squandered the opportunity to correct our current course over the last 30 years, they conclude, and much must change if the world is to avoid the serious consequences of overshoot in the 21st century.

When The Limits to Growth was first published in 1972, most economists, along with many industrialists, politicians, and Third World advocates raised their voices in outrage at the suggestion that population growth and material consumption need to be reduced by deliberate means. Over the years, Limits was attacked by many who didn’t understand or misrepresented its assertions, dismissing it as Malthusian hyperbole. But nothing that has happened in the last 30 years has invalidated the book’s warnings.

On the contrary, as noted energy economist Matthew Simmons recently wrote, “The most amazing aspect of the book is how accurate many of the basic trend extrapolations … still are some 30 years later.” For example, the gap between rich and poor has only grown wider in the past three decades. Thirty years ago, it seemed unimaginable that humanity could expand its numbers and economy enough to alter the Earth’s natural systems. But experience with the global climate system and the stratospheric ozone layer have proved them wrong.

All the environmental and economic problems discussed in Limits to Growth have been treated at length before. There are hundreds of books on deforestation, global climate change, dwindling oil supplies, and species extinction. Since The Limits to Growth was first published 30 years ago, these problems have been the focus of conferences, scientific research, and media scrutiny.

What makes Limits to Growth: The 30-Year Update unique, however, is that it presents the underlying economic structure that leads to these problems. Moreover, Limits is a valuable reference and compilation of data. The authors include 80 tables and graphs that give a comprehen- sive, coherent view of many problems. The book will undoubtedly be used as a text in many courses at the college level, as its two earlier versions have been.

WORLD 3 The World3 computer model is complex, but its basic structure is not difficult to understand. It is based in system dynamic—a method for studying the world that deals with understanding how complex systems change over time. Internal feedback loops within the structure of the system influence the entire system behavior. World3 keeps track of stocks such as population, industrial capital, persistent pollution, and cultivated land. In the model, those stocks change through flows such as births and deaths; investment and depre- ciation; pollution generation and pollution assimilation; land erosion, land development, and land removed for urban and industrial uses. The model accounts for positive and negative feedback loops that can radically affect the outcome of various scenarios. It also develops nonlinear relationships. For example, as more land is made arable, what’s left is drier, or steeper, or has thinner soils. The cost of coping with these problems dramatically raises the cost of developing the land—a nonlinear relationship. Feedback loops and nonlinear relationships make World3 dynami- cally complex, but the model is still a simplification of reality. World3 does not distinguish among different geographic parts of the world, nor does it represent separately the rich and the poor. It keeps track of only two aggregate pollutants, which move through and affect the environment in ways that are typical of the hundreds of pollutants the economy actually emits. It omits the causes and consequences of violence. And there is no military capital or corruption explicitly represented in World3. Incorporating those many distinctions, how- ever, would not necessarily make the model better. And it would make it very much harder to comprehend. This probably makes World3 highly optimistic. It has no military sector to drain capital and resources from the productive economy. It has no wars to kill people, destroy capital, waste lands, or generate pollution. It has no ethnic strife, no corruption, no floods, earthquakes, nuclear accidents, or AIDS epidemics. The model represents the uppermost possibilities for the “real” world.

Readers who want to reproduce the World 3 scenarios of the book can do so themselves, because the authors have prepared interactive World 3 CDs. To order disks, please see back of title page.

The authors developed World3 to understand the broad sweep of the future—the possible behavior patterns, through which the human economy will interact with the carrying capacity of the planet over the coming century.

World3’s core question is, How may the expanding global popula- tion and materials economy interact with and adapt to the earth’s limited carrying capacity over the coming decade? The model does not make predictions, but rather is a tool to understand the broad sweeps and the behavioral tendencies of the system.

Technology Markets The most common criticisms of the original World3 model were that it underestimated the power of technology and that it did not represent adequately the adaptive resilience of the free market. Impressive—and even sufficient—technological advance is conceivable, but only as a consequence of determined societal decisions and willingness to follow up such decisions with action and money. Technological advance and the market are reflected in the model in many ways. The authors assume in World3 that markets function to allocate limited investment capital among competing needs, essentially without delay. Some technical improvements are built into the model, such as birth control, resource substitution, and the green revolution in agriculture. But even with the most effective technologies and the greatest economic resilience that seems possible, if those are the only changes, the model tends to generate scenarios of collapse. One reason technology and markets are unlikely to prevent overshoot and collapse is that technology and markets are merely tools to serve goals of society as a whole. If society’s implicit goals are to exploit nature, enrich the elites, and ignore the long term, then society will develop technologies and markets that destroy the environment, widen the gap between rich and poor, and optimize for short-term gain. In short, society develops technologies and markets that hasten a collapse instead of preventing it.

The second reason for the vulnerability of technology is that adjustment mechanisms have costs. The costs of technology and the market are reckoned in resources, energy, money, labor, and capital.

THE DRIVING FORCE: EXPONENTIAL GROWTH

For more than a century, the world has been experiencing exponential growth in a number of areas, including population and industrial production. Positive feedback loops can reinforce and sustain exponential growth. In 1650, the world’s population had a doubling time of 240 years. By 1900, the doubling time was 100 years. When The Limits to Growth was published in 1972, there were under 4 billion people in the world. Today, there are more than 6 billion, and in 2000 we added the equivalent of nine New York cities.

Another area of exponential growth has been the world economy. From 1930 to 2000, the money value of world industrial output grew by a factor of 14—an average doubling time of 19 years. If population had been constant over that period, the material standard of living would have grown by a factor of 14 as well. Because of population growth, however, the average per capita output increased by only a factor of five.

Moreover, in the current system, economic growth generally occurs in the already rich countries and flows disproportionately to the richest people within those countries. Thus, according to the United Nations Development Program, the 20 percent of the world’s people who lived in the wealthiest nations had 30 times the per capita income of the 20 percent who lived in the poorest nations. By 1995 the average income ratio between the richest and poorest 20 percent had increased from 30:1 to 82:1.

Only eight percent of the world’s people own a car. Hundreds of millions of people live in inadequate houses or have no shelter at all—much less refrigerators or television sets. Social arrangements common in many cultures systematically reward the privileged, and it is easier for rich populations to save, invest, and multiply their capital.

THE LIMITS Limits to growth include both the material and energy that are extracted from the Earth, and the capacity of the planet to absorb the pollutants that are generated as those materials and energy are used. Streams of material and energy flow from the planetary sources through the economic system to the planetary sinks where wastes and pollutants end up. There are limits, however, to the rates at which sources can produce these materials and energy without harm to people, the economy, or the earth’s processes of regeneration and regulation. Resources can be renewable, like agricultural soils, or nonrenew- able, like the world’s oil resources. Both have their limits. The most obvious limit on food production is land. Millions of acres of cultivated land are being degraded by processes such as soil erosion and salinization, while the cultivated area remains roughly constant. Higher yields have compensated somewhat for this loss, but yields cannot be expected to increase indefinitely. Per capita grain production peaked in 1985 and has been trending down slowly ever since. Exponential growth has moved the world from land abundance to land scarcity. Within the last 35 years, the limits, especially of areas with the best soils, have been approached.

Another limit to food production is water. In many countries, both developing and developed, current water use is often not sustain- able. In an increasing number of the world’s watersheds, limits have already been reached. In the U.S. the Midwestern Ogalallah aquifer in Kansas is overdrawn by 12 cubic kilometers each year. Its depletion has so far caused 2.46 million acres of farmland to be taken out of cultivation. In an increasing number of the world’s watersheds, limits have already, indisputably, been exceeded. In some of the poorest and richest economies, per capita water withdrawals are going down because of environmental problems, rising costs, or scarcity.

Another renewable resource is forests, which moderate climate, control floods, and harbor species, from rattan vines to dyes and sources of medicine. But today, only one-fifth of the planet’s original forest cover remains in large tracts of undisturbed natural forests. Although forest cover in temperate areas is stable, tropical forest area is plummeting.

From 1990 to 2000, the FAO reports that more than 370 million acres of forest cover—an area the size of Mexico—was converted to other uses. At the same time that forests decline, demand for forest products is growing. If the loss of 49 million acres per year, typical in the 1990s, continues to increase at 2 percent per year, the unprotected forest will be gone before the end of the century.