Limits to Growth (1972) and Beyond the Limits (1992)

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Limits to Growth (1972) and Beyond the Limits (1992)

Published at the height of the oil crisis in the 1970s, the Limits to Growth study is credited with lifting environmental concerns to an international and global level. Its fundamental conclusion is that if rapid growth continues unabated in the five key areas of population, food production, industrialization, pollution , and consumption of nonrenewable natural resources , the planet will reach the limits of growth within 100 years. The most probable result will be a "rather sudden and uncontrollable decline in both population and industrial capacity."

The study grew out of an April 1968 meeting of 30 scientists, educators, economists, humanists, industrialists, and national and international civil servants who had been brought together by Dr. Aurelio Peccei, an Italian industrial manager and economist. Peccei and the others met at the Accademia dei Lincei in Rome to discuss the "present and future predicament of man," and from their meeting came the Club of Rome . Early meetings of the club resulted in a decision to initiate the Project on the Predicament of Mankind, intended to examine the array of problems facing all nations. Those problems ranged from poverty amidst plenty and environmental degradation to the rejection of traditional values and various economic disturbances.

In the summer of 1970, Phase One of the project took shape during a series of meetings in Bern, Switzerland and Cambridge, Massachusetts. At a two-week meeting in Cambridge, Professor Jay Forrester of the Massachusetts Institute of Technology (MIT) presented a global model for analyzing the interacting components of world problems. Professor Dennis Meadows led an international team in examining the five basic components, mentioned above, that determine growth on this planet and its ultimate limits. The team's research culminated in the 1972 publication of the study, which touched off intense controversy and further research.

Underlying the study's dramatic conclusions is the central concept of exponential growth , which occurs when a quantity increases by a constant percentage of the whole in a constant time period. "For instance, a colony of yeast cells in which each cell divides into two cells every ten minutes is growing exponentially," the study explains. The model used to capture the dynamic quality of exponential growth is a System Dynamics model, developed over a 30-year period at MIT, which recognizes that the structure of any system determines its behavior as much as any individual parts of the system. The components of a system are described as "circular, interlocking, sometimes time-delayed." Using this model (called World3), the study ran scenarioswhat-if analysesto reach its view of how the world will evolve if present trends persist.

"Dynamic modeling theory indicates that any exponentially growing quantity is somehow involved with a positive feedback loop," the study points out. "In a positive feedback loop a chain of cause-and-effect relationships closes on itself, so that increasing any one element in the loop will start a sequence of changes that will result in the originally changed element being increased even more."

In the case of world population growth , the births per year act as a positive feedback loop. For instance, in 1650, world population was half a billion and was growing at a rate of 0.3 percent a year. In 1970, world population was 3.6 billion and was growing at a rate of 2.1 percent a year. Both the population and the rate of population growth have been increasing exponentially. But in addition to births per year, the dynamic system of population growth includes a negative feedback loop: deaths per year. Positive feedback loops create runaway growth, while negative feedback loops regulate growth and hold a system in a stable state. For instance, a thermostat will regulate temperature when a room reaches a certain temperature, the thermostat shuts off the system until the temperature decreases enough to restart the system. With population growth, both the birth and death rates were relatively high and irregular before the Industrial Revolution. But with the spread of medicines and longer life expectancies, the death rate has slowed while the birth rate has risen. Given these trends, the study predicted a worldwide jump in population of seven billion over 30 years.

This same dynamic of positive and negative feedback loops applies to the other components of the world system. The growth in world industrial capital, with the positive input of investment, creates rising industrial output, such as houses, automobiles, textiles, consumer goods, and other products. On the negative feedback side, depreciation, or the capital discarded each year, draws down the level of industrial capital. This feedback is "exactly analogous to the death rate loop in the population system," the study notes. And, as with world population, the positive feedback loop is "strongly dominant," creating steady growth in worldwide industrial capital and the use of raw materials needed to create products.

This system in which exponential growth is occurring, with positive feedback loops outstripping negative ones, will push the world to the limits of exponential growth. The study asks what will be needed to sustain world economic and population growth until and beyond the year 2000 and concludes that two main categories of ingredients can be defined. First, there are physical necessities that support all physiological and industrial activity: food, raw materials, fossil and nuclear fuels, and the ecological systems of the planet that absorb waste and recycle important chemical substances. Arable land , fresh water, metals, forests, and oceans are needed to obtain those necessities. Second, there are social necessities needed to sustain growth, including peace, social stability , education, employment, and steady technological progress.

Even assuming that the best possible social conditions exist for the promotion of growth, the earth is finite and therefore continued exponential growth will reach the limits of each physical necessity. For instance, about 1 acre (0.4 ha) of arable land is needed to grow enough food per person. With that need for arable land, even if all the world's arable land were cultivated, current population growth rates will still create a "desperate land shortage before the year 2000," the study concludes. The availability of fresh water is another crucial limiting factor, the study points out. "There is an upper limit to the fresh water runoff from the land areas of the earth each year, and there is also an exponentially increasing demand for that water."

This same analysis is applied to nonrenewable resources , such as metals, coal , iron, and other necessities for industrial growth. World demand is rising steadily and at some point demand for each nonrenewable resource will exceed supply, even with recycling of these materials. For instance, the study predicts that even if 100 percent recycling of chromium from 1970 onward were possible, demand would exceed supply in 235 years. Similarly, while it is not known how much pollution the world can take before vital natural processes are disrupted, the study cautions that the danger of reaching those limits is especially great because there is usually a long delay between the time a pollutant is released and the time it begins to negatively affect the environment .

While the study foretells worldwide collapse if exponential growth trends continue, it also argues that the necessary steps to avert disaster are known and are well within human capabilities. Current knowledge and resources could guide the world to a sustainable equilibrium society provided that a realistic, long-term goal and the will to achieve that goal are pursued.

The sequel to the 1972 study, Beyond the Limits, was not sponsored by the Club of Rome, but it is written by three of the original authors. While the basic analytical framework remains the same in the later workdrawing upon the concepts of exponential growth and feedback loops to describe the world systemits conclusions are more severe. No longer does the world only face a potential of "overshooting" its limits. "Human use of many essential resources and generation of many kinds of pollutants have already surpassed rates that are physically sustainable," according to the 1992 study. "Without significant reductions in material and energy flows, there will be in the coming decades an uncontrolled decline in per capita food output, energy use, and industrial output."

However, like its predecessor, the later study sounds a note of hope, arguing that decline is not inevitable. To avoid disaster requires comprehensive reforms in policies and practices that perpetuate growth in material consumption and population. It also requires a rapid, drastic jump in the efficiency with which we use materials and energy.

Both the earlier and the later study were received with great controversy. For instance, economists and industrialists charged that the earlier study ignored the fact that technological innovation could stretch the limits to growth through greater efficiency and diminishing pollution levels. When the sequel was published, some critics charged that the World3 model could have been refined to include more realistic distinctions between nations and regions, rather than looking at all trends on a world scale. For instance, different continents, rich and poor nations, North, South, and East, various regionsall are different, but those differences are ignored in the model, thereby making it unrealistic even though modeling techniques have evolved significantly since World3 was first developed.

See also Sustainable development

[David Clarke ]



Meadows, D., et al. The Limits to Growth: A Report for The Club of Rome's Project on the Predicament of Mankind. New York: Universe Books, 1972.

Meadows, D., D. L. Meadows, and J. Randers. Beyond the Limits: Confronting Global Collapse, Envisioning a Sustainable Future. Post Mills, VT: Chelsea Green, 1992.