The Limits to Growth

Club of Rome

The Limits to Growth is a 1972 book modeling the consequences of a rapidly growing world population and finite resource supplies, commissioned by the Club of Rome (a global think tank) and firstly presented at the 3. St. Gallen Symposium (an annual conference taking place at the University of St. Gallen in Switzerland, aimed at fostering intergenerational and intercultural dialogue between the decision makers of today and tomorrow). The book echoes some of the concerns and predictions of the Reverend Thomas Robert Malthus in ‘An Essay on the Principle of Population’ (1798).

Its authors were Donella H. Meadows, Dennis L. Meadows, Jørgen Randers, and William W. Behrens III. The book used World3, a computer model to simulate the consequence of interactions between the Earth’s and human systems. Five variables were examined in the original model, on the assumptions that exponential growth accurately described their patterns of increase, and that the ability of technology to increase the availability of resources grows only linearly. These variables are: world population, industrialization, pollution, food production and resource depletion.

The authors intended to explore the possibility of a sustainable feedback pattern that would be achieved by altering growth trends among the five variables. The most recent updated version was published in 2004 under the name ‘Limits to Growth: The 30-Year Update.’ Donnella Meadows, Jørgen Randers, and Dennis Meadows have updated and expanded the original version. They had previously published ‘Beyond the Limits’ in 1993 as a 20 year update on the original material. In 2008 Graham Turner in Australia published a paper called ‘A Comparison of ‘The Limits to Growth’ with Thirty Years of Reality.’ It found that changes in industrial production, food production and pollution are all in line with the book’s predictions of economic and societal collapse in the 21st century.

The purpose of ‘The Limits to Growth’ was not to make specific predictions, but to explore how exponential growth interacts with finite resources. Because the size of resources is not known, only the general behavior can be explored. The authors state in a subsection titled ‘The Purpose of the World Model’:

‘In this first simple world model, we are interested only in the broad behavior modes of the population-capital system. By behavior modes we mean the tendencies of the variables in the system (population or pollution, for example) to change as time progresses. A variable may increase, decrease, remain constant, oscillate, or combine several of these characteristic modes. For example, a population growing in a limited environment can approach the ultimate carrying capacity of that environment in several possible ways. It can adjust smoothly to an equilibrium below the environmental limit by means of a gradual decrease in growth rate, as shown below. It can overshoot the limit and then die back again in either a smooth or an oscillatory way, also as shown below. Or it can overshoot the limit and in the process decrease the ultimate carrying capacity by consuming some necessary nonrenewable resource, as diagrammed below. This behavior has been noted in many natural systems. For instance, deer or goats, when natural enemies are absent, often overgraze their range and cause erosion or destruction of the vegetation.’

‘A major purpose in constructing the world model has been to determine which, if any, of these behavior modes will be most characteristic of the world system as it reaches the limits to growth. This process of determining behavior modes is ‘prediction’ only in the most limited sense of the word. The output graphs reproduced later in this book show values for world population, capital, and other variables on a time scale that begins in the year 1900 and continues until 2100. These graphs are not exact predictions of the values of the variables at any particular year in the future. They are indications of the system’s behavioral tendencies only.’

‘The difference between the various degrees of ‘prediction’ might be best illustrated by a simple example. If you throw a ball straight up into the air, you can predict with certainty what its general behavior will be. It will rise with decreasing velocity, then reverse direction and fall down with increasing velocity until it hits the ground. You know that it will not continue rising forever, nor begin to orbit the earth, nor loop three times before landing. It is this sort of elemental understanding of behavior modes that we are seeking with the present world model. If one wanted to predict exactly how high a thrown ball would rise or exactly where and when it would hit the ground, it would be necessary to make a detailed calculation based on precise information about the ball, the altitude, the wind, and the force of the initial throw. Similarly, if we wanted to predict the size of the earth’s population in 1993 within a few percent, we would need a very much more complicated model than the one described here. We would also need information about the world system more precise and comprehensive than is currently available.’

One key idea within the The Limits to Growth is the notion that if the rate of resource use is increasing, the amount of reserves cannot be calculated by simply taking the current known reserves and dividing by the current yearly usage, as is typically done to obtain a static index. The static reserve numbers assume that the usage is constant, and the exponential reserve assumes that the growth rate is constant. The exponential index has been interpreted as a prediction of the number of years until the world would ‘run out’ of various resources, both by environmentalist groups calling for greater conservation and restrictions on use, and by skeptics criticizing the index when supplies failed to run out.

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