Week 1

CHAPTER 2 The Concept of Sustainability

2.1 IS HUMANITY’S PATH UNSUSTAINABLE?

Unpredicted societal collapse is an occasional feature of the history of humanity. The classic case is that of Easter Island in the southeastern Pacific Ocean. It is very remote, and was not settled until about 800 CE. When the Polynesians arrived, they began to cut trees to create farmland and to make canoes. Soon they began to erect the large statues for which the island is famous, and trees were used to transport the statues and erect them. Over time, the island’s trees were all cut for these purposes.

The lack of trees meant that Easter Island had no firewood, mulch, or canoes. Without the ability to catch dolphins from canoes, and with the depletion of nesting birds, the population came under severe pressure, and the island was too remote for help to come. There were no alternatives to a severe and ultimately permanent population collapse.

Easter Island is a special case, certainly, but it is not hard to find other cases in which the misuse of technology has forever changed part of the planet—the acid mine drainage and heavy metal pollution around Butte, Montana, in the western United States is an example.

The discussion of collapse can be generalized by examining the alternative behavioral patterns for complex systems shown in  Figure 2.1 . The exponential path ( Figure 2.1a ) traces the path of social progress for some 200 years. This pattern occurs when there are no constraints to growth or when innovation causes apparent limits to recede. The s-shaped curve ( Figure 2.1b ) is characteristic of the system with fixed constraints in which action is controlled by feedback based on a sense of the distance to the limits. To manage the smooth approach, the system must respond without significant lags and with accurate knowledge of the distance yet to go.

Figure 2.1

Four typical behavior patterns for complex systems. (Adapted from D.H. Meadows, D.L. Meadows, and J. Randers, Beyond the Limits, White River Junction, VT: Chelsea Green, 1992.)

The curve showing oscillatory behavior ( Figure 2.1c ) is typical of systems where feedback mechanisms are inaccurate and responses are slow. At the point that awareness of some limit becomes sufficient to produce action, it is too late to avoid overstep-ping the limits and the system continues to move beyond what appears to be some long-run sustainable state. If the stress produced by the overshoot does not completely degrade the system, subsequent corrections can enable the system to oscillate about and approach the limit. Curve (d) depicts initial behavior somewhat like the third curve, but with a critical difference. Here the system is insufficiently robust, corrections are insufficient, and collapse occurs. This is the Easter Island trajectory.

It is important to note that the initial stages of these curves are quite similar. We imagine that we are close to the origin and further imagine intuitively that we are on the exponential growth pattern. If we are not, we must look sustainability in the face and think hard about the robustness and stability of our technological society.

It is useful at this point to define what we mean by sustainability. Many have tried to formulate succinct definitions, two of which we feel have particular merit. John Ehrenfeld’s is conceptual: “ Sustainability  is the possibility that human and other forms of life will flourish on the planet forever.” The International Institute of Environment and Development defines sustainable development (often used as a synonym for  sustainability ) as “A development path that can be maintained indefinitely because it is socially desirable, economically viable, and ecologically sustainable.” The words have resonance, but offer minimal guidance to engineers, scientists, political leaders, and citizens. What specific actions will move us in the direction of sustainability?