What is Sustainability?
Because of the many interpretations of sustainability, the following are given as some useful working definitions:
The Brundtland Commission
"Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs." ---
Brundtland Commission, 1983
The Daly Rules for Sustainability
University of Maryland School of Public Policy professor and former Chief Economist for the World Bank Herman E. Daly suggests the following three operational rules defining the condition of ecological sustainability:
1. Renewable resources such as fish, soil, and groundwater must be used no faster than the rate at which they regenerate.
2. Nonrenewable resources such as minerals and fossil fuels must be used no faster than renewable substitutes for them can be put into place.
3. Pollution and wastes must be emitted no faster than natural systems can absorb them, recycle them, or render them harmless.
One way to implement these rules is to consider how the use of renewable resources can be compared to the rate of renewal, as follows:
Consumption of State of Environment Sustainability
renewable
resources
___________________________________________________________________
More than nature's Environmental degradation Not sustainable
ability to
replenish
___________________________________________________________________
Equal to nature's Environmental equilibrium Steady-state
ability to Sustainability
replenish
___________________________________________________________________
Less than nature's Environmental renewal Sustainable
ability to development
replenish
___________________________________________________________________
A Systems Approach to Sustainability
Systems analysis offers some clues about the nature of sustainability. By reasoning about how systems behave under a variety of conditions, we can perhaps better understand the properties of a sustainable water resources system.
Duration: A basic idea that underlies sustainability is the concept of duration. It is assumed that the system will exist for a long period of time. The implication is that humans would not invest a great deal of effort in constructing a system that would not last for a long time. This leads to a first rule of thumb for estimating sustainability: to what extent will the system continue in its current pattern of human use over an extended time span. There are many things that can influence the nature of a system, however, some of what are considered below.
Rate of Change: When examining a system, we should ask how quickly it can change? Systems are very sensitive to rate of change, especially the rate of change of inputs. Too great a change in too short a time leads to undesirable or unstable system behavior. Examples show that a sudden spike or step function will lead to unexpected results. This holds true for changes in both directions. A sudden upswing or drop in prices can be undesirable in either case. We may call the results inflation or depression, but these terms are just ways of naming a set of unwanted effects.
Static vs. Dynamic Systems: It was once assumed that our human and natural systems could reach a state of equilibrium. Models have been built around ideas like comparative statics that depict how elements exist in balance. This research implies that some kind of steady state is the norm. More recently, however, it appears that human systems embody a set of conditions that may seek equilibrium in a dynamic sense but never reach it. This may be the case because the forces that impact the system are changing faster than the system can adjust, thus making it impossible to reach equilibrium.
Buffering: It is important to realize that the buffering capacity of a system has limits. This capacity also determines the amount of “wiggle room” that we have to carry out policies that provide benefits without real damage to other parts of the system. The system is not so tightly determined that no changes can be made, nor is it so flexible that infinite action will make no difference. The balance lies somewhere between. Possibly a good example of this situation is national debt, which can continue for perhaps very long periods but which ultimately lead to serious system degradation.
Deterministic vs. Stochastic Systems: In days gone by, human relationships with the physical world have been defined in deterministic terms (i.e, a change in x must have an effect on y). However, now it appears that our systems are more stochastic. A change in x thus will change y but only with some probability. Multiple causes lead to multiple effects with probabilities mediating each link in the system. Needless to say, such systems are much harder to model. The nature of the system makes it difficult to intervene in a way that is highly likely to produce only positive results. It is almost certain that the so-called law of unintended consequences is rooted in this system property, even assuming that all parts of the system are well known, which is not usually the case.
A corollary of this stochastic property involves the nature of sustainability. When we deal with such systems, all the variables exist in a probabilistic context. Each one can be represented by some mean value, but in truth has its own probability distribution function. This means that the very nature of system sustainability is probabilistic and can only be stated in terms, for example, of minimum and maximum values. Needless to say, we are far from being able to do this now in any reasonable way.
Wild Cards and Tipping Points: Large-scale patterns seem to suggest that long-term trends may continue for long periods without much change, even though the results may be harmful to the system that represents civilization. The structure becomes increasingly unstable. If a wild card event occurs with some probability, this can cause rapid unexpected change in the system, in the same way that a input step function might. This kind of tipping point is hard to anticipate or prepare for. It might well be forecast, but prevailing forces tend to discount it as an unlikely event compared to daily occurrences. An example of this behavior might be the recurrent tendency to build in flood plains, in which the demonstrated benefits of the location are thought to outweigh the small chance that a flood will occur.
Reversibility: Here it may be useful to connect these ideas with the concept of duration discussed above. The time frame of an individual is greatly different than that of the system (i.e., civilization) within which he exists. Rational decisions on an individual basis may, especially in the aggregate, lead to the gradual degradation of the system as a whole. Depending on the factors noted in the preceding paragraph, various outcomes can occur. Gradual and irreversible negative changes in the whole system may occur; such changes may in fact be reversible, but only at a cost considered exorbitant by those then living. Alternatively, the negative changes that originally happened gradually may be stopped or reversed, but only by measures that must be carried out in a short time. This would be like sending a step function through the system, which is usually a destabilizing action. All these effects lead to outcomes for the whole system, which can well make it unsustainable. History offers some interesting examples that look very much like exactly this process. In parts of the Middle East we can detect from satellite the remains of irrigation canals that were constructed by successive civilizations, which occupied the same region. There are repeated cycles of canal building, followed by increasing soil salination, followed later by the collapse of the central government. We cannot push this example too far, since there are clearly many other things besides water that can contribute to this kind of change. But it certainly would appear that a progressive inability to maintain an agricultural food supply, in an arid region, would not promote the stability of the government then in existence.
Extreme Conditions: When attempting to find solutions to system problems, it is sometimes possible to come up with some type of extreme solution, or to gradually choose the trend of progressively more extreme conditions. In most cases this state of affairs will not promote the sustainability of the system. Historical examples include the gradual population increase that eventually exceeds the available resource base, which may include water, agriculture, or other resources. The conclusion is that any extreme solution to a problem is suspect, since it may include hidden negative factors that will impair or destroy the system as a whole.
Sustainability in the Literature
A method of searching based on words and phrases has been developed by Google, and offers a quick way to assess the frequency of occurrence of topics that might be considered especially significant.
For comparison, some other phrases were tested, based on the common use of wording in public policy making in recent years: Climate Change and Strategic Planning are shown, because of their popularity either now or in the recent past. The results show a rapid rise in Sustainability in recent years.
The trend graphs can be found at:
More recently, Google has developed an interactive trends comparison capability, which can be accessed on line. One result from this analysis is shown here, although the search is done dynamically for each incident. Hence, results can vary depending on when the search is carried out. These results are for the years 2004 to 2014.
The graph shown is carried out for a worldwide geography, using the Law and Government category, and using web documents for searching. In most of the cases that have been analyzed this way, the sustainability topic has continued to compare favorably with climate change, while strategic planning has lagged behind.
The trend comparison graph is at: https://drive.google.com/file/d/0B8FZ9WSEG7a2blpIQVpyYnlUek0/view?usp=sharing
One very useful diagram of how to think about sustainability can be seen at
BIBLIOGRAPHY
An excellent Wikipedia article on sustainability can be found at