FS II 98-402
Weak and Strong Conditions for Sustainable Development:
Concepts and Policy Implications
by
Clem Tisdell*
*Professor of Economics, The University of Queensland, Brisbane 4072, Australia. Revised version of a paper presented at a symposium in the WZB, 1997.
I wish to thank Professor Udo E. Simonis and participants for useful comments on this occasion.
The usual caveat applies.
Wissenschaftszentrum Berlin für Sozialforschung gGmbH (WZB) Science Center Berlin
Reichpietschufer 50, D-10785 Berlin
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A b stra ct
As is well known, there are a variety of concepts of sustainable development. This paper concentrates on the main economic concept of sustainable development and discusses weak and strong conditions for it, taking into account the scope for substituting different types of capital - man-made capital (physical and human) and natural resource or environmental capital.
A simple diagrammatic approach is adopted which should help to clarify controversies in this area, and allow also for the views of ecocentric persons. The possibility is explored that the conditions for sustainable development may differ between countries - some are able to adopt stronger conditions than others. In addition, some of the implications of weak and strong sustainability for project evaluation are explored and an option is raised about offset policies as a means for satisfying strong sustainability conditions.
1. Introduction
A variety of concepts and conditions for sustainable development have emerged, and for some people, this has created confusion (Tisdell, 1993, Ch. 9). Many writers have failed to distinguish between the normative and positive aspects of the issues involved and this has added to the confusion. It is in fact a strength that a variety of concepts of sustainable development have emerged but it is important to specify these concepts carefully and distinguish between them. In some writings it is not clear what the authors want to sustain and why they want to sustain it.
Sometimes the focus is on a ‘single’ dimension such as the achievement of economic sustainability, social sustainability or biophysical sustainability and on other occasions, the focus is of a multi-dimensional nature requiring simultaneous satisfaction of conditions for economic, social and biophysical sustainability. The latter may be assumed to include ecological sustainability.
In reality, those conditions for sustainability, which were probably first stated by Barbier (1987), may be rarely satisfied by socio-economic systems and by methods or techniques of economic production. Indeed, writers like Georgescu-Roegen (1971, 1976) argue that in view of the physical law of entropy, it is virtually impossible to achieve truly sustainable economic systems from the biophysical point of view. One’s only choice is about the speed at which to run a system down physically.
However, there are ways in which the ‘decline’ of a system can be slowed, e.g., by reducing economic demands on it, or discovering new techniques which indirectly may reduce demands on the system. In some cases also where the conditions for sustainability are not satisfied for the maintenance of a system, economic reforms or social innovations may increase its sustainability. The desirability of such reforms of course depends, of course, on what wants to sustain.
In this paper, I outline the main economic goal of sustainable development and point to some of its limitations, then discuss concepts of capital, capital substitution and sustainability and consider some possible policy
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implications of these. Concepts of resources and capital substitution are at the heart of the debate about policies to achieve sustainable development.
2. The Main Economic Goal of Sustainable Development and some of its Limitations
Here I shall concentrate on the principal economic concept of sustainable development, namely that it is development that ensures that income per head of future generations is no less than that of current generations (Tietenberg, 1988; Pearce et al., 1989). This may be broadly interpreted to mean that the standard of living or economic welfare of future generations be not less than that of present generations, even though the way in which we should measure these variables is far from clear.
Note that the economic concept is purely an anthropocentric one. It is only generations of human beings which are to count. While this simplifies the issue, it does not avoid controversy. Controversy exists about whether this anthropocentric goal ought to be the goal of society and if it is the goal, how it can be achieved.
Those with an ecocentric bent find such an objective to be too limited.
Many believe that other sentient beings should be taken into account in the welfare calculus (Blackorby and Donaldson, 1992), or that the survival of other species, irrespective of human wishes (Sagoff, 1988; Leopold, 1949), should form part of society’s objective function. This implies that other sentient beings and species should not be regarded purely as instruments for the fulfilment of human satisfaction. I shall return to this point of view later.
In addition, there are anthropocentric persons who are not convinced of the desirability of the objective that the income of future generations be not less than that of present generations. Beckerman (1994, 1996) is, for example, anthropocentric but suggests that the above rule can give rise to poor social choices. For example, suppose that there are two alternative possible development paths. One ensures that the income of future
generations is equal to that of present generations or increases slightly.
The other alternative ensures that the income of future generations except the last one, is much higher than that of present generations and the income of the last generation is marginally less than that of present generations. Application of the sustainability rule given above will result in choice of the former development path and rejection of the latter.
However, the total utility obtained from the latter could be higher than the former and on the face of it, it seems to be socially superior.
Total utility maximisation of the utility obtained by all generations can result in quite different development choices to that of the above mentioned intergenerational equity objective, as can this type of utility maximisation subject to less restrictive intergenerational equity constraints.
Rawls’ principle of justice (Rawls, 1971) is often used in support of the principle that the income of future generations should not be less than that of present generations. It is argued that every person could have been born at a different time and in the position of any other person. Therefore, not knowing what position and time individuals might occupy prior to birth, if a social agreement could be reached prior to birth, all would opt for equality of income unless inequality happened to be to the advantage of all. However, as pointed out elsewhere (Tisdell, 1993, Ch. 9), Rawls’
principle is not completely convincing.
It assumes, for example, that individuals can only be born as human beings and are only born once. It may be true, but not everyone believes it, e.g. Hindus. Secondly, it does not consider the possibility that some individuals who could have been born, are not, due to birth control. The set of those to be bom is taken as given whereas it may not be given in advance. All of these factors raise philosophical dilemmas for Rawls’
approach. Apart from this, however, it is doubtful whether individuals are as risk-averse as Rawls supposes. If they are not, then they may choose a development path for which the income of some future generations is below that of current generations. Note that Rawls’ rule is sometimes described as a maximum gain rule. It is very security biased.
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Given a choice, each individual might for instance opt to maximise his/her expected utility subject to being assured some minimum standard of living. This implies that individuals are prepared to take risks in order to improve their expected economic lot. As a result, individuals could rationally choose a development path for which the income of some future generations are below those at present but for which the income of most future generations is well above that of present generations.
Time, generations
Figure 1: The income achieved by an individual is liable to vary with the generation in which he/she is bom. This figure shows some alternative possibilities. Path (1) is
sustainable but the other two are not yet they may be socially preferable.
Figure 1 illustrates the point. At the initial point, two alternative development paths are available to society,(1) and (2). These give individuals the possibility of incomes shown by line ABC or by curve ADE.
The individual’s income will depend upon when he or she is born, that is into which generation birth takes place. The horizon for human existence is tn. The individual wishes to be assured of a minimum standard of living of OF. Given that the individual is equally likely to be bom into any
generation, his or her expected income1 for development path (1) is BH, and for development path (2) is in the neighbourhood of DJ. Both paths ensure that the individual’s standard of living constraint is met. Thus the unsustainable development path (2) would rationally be chosen because it yields the highest expected income and satisfies the minimum income constraint, even though it is also a path for which the income of some future generations is below that of current generations. It therefore does not satisfy the economic criterion for sustainability, namely that the income of future generations be not less than that of present generations.
Note that the effect of the economic sustainability criterion depends on whether it is to be applied for each generation or only to the existing generations. If the criterion is repeatedly applied by every generation, then it implies that the only acceptable development paths are those that show no decline whatsoever in income levels. This would have the absurd result that a path like AKL in Figure 1 would be less preferred than path ABC, even though incomes of future generations are always greater for path AKL.
3. Digression on Resources, Natural Environments and Economic Sustainability
Neoclimatical growth theory (Solow, 1956, 1957, 1974; Swan, 1956;
Stiglitz, 1979) and new growth theories (Romer, 1986) assumed that economic growth is not limited by the natural environment. The early Solow-Swan models assumed that natural output is merely a function of labour (L) and capital (K), where fundamentally capital is assumed to be physical man-produced capital.
In these earlier models, for simplicity and empirical purposes, the production function was assumed to be of a Cobb-Douglas form. It followed that provided capital accumulation (via savings) grew least at a rate as fast as that of the labour force (assumed to be a constant proportion of the population) income per head of population would be non
declining and could be sustained without limit. Capital accumulation was therefore the key to perpetual economic progress, although more
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sophisticated forms of the production function were later used, such as constant elasticity of substitution (CES) and variable elasticity of substitution (VES) production functions, the basic message was that capital accumulation is the touchstone for continually reducing economic scarcity.
Although the earliest macroeconomic production functions of Solow and Swan were of the form
Yt = f(U K t) (1)
this formulation was later augmented by Solow to take account of technological progress which he introduced in a exogenous manner so that the production function answered the growth form
Y, = F(Lt, K) h(t) (2)
where h(f) > 1 and h ' > 0 and represents the level of technology.
Technological progress in this case continually raises productivity, and so income per capita can rise even if the rate of capital accumulation is somewhat slower than the rate of population growth. The exact mathematical relationship depends on the assumed form of (2). The upshot is that technological progress can also be a factor moving the world towards a situation of economic bounty.
This fits well with the views of Karl Marx (1954) and Friedrich Engels (1978). Marx believed that capital accumulation was the main force and hope for reducing economic scarcity. Although he objected to the capitalist economic system on social grounds, he nevertheless believed that capital accumulation would be the most important means for economic advancement, a message enthusiastically embraced by Lenin, Stalin and Mao Tse-tung. Engels in criticising Malthus specifically pointed to capital accumulation and scientific progress as means for increasing economic production and overcoming limits to growth.
Naturally there are many complications which can be considered in relation to neoclassical economic growth theory. For example, the measurement of capital is not straightforward, the productivity of capital depends on its vintage, new technologies may be embodied in capital or disembodied, and technological progress may be not neutral in its effects
on employment of labour relative to capital. Furthermore, as became apparent from the research of E.F. Denison (1962), quantities of labour and capital no longer are the main sources of economic growth in more advanced economies such as the US. They were outweighed in importance by increased education and improved technology, together with other factors such as increased productivity due to greater market size.
A clear deficiency of the Solow model as augmented for technological progress is that this element is treated as exogeneous and account is not taken of human capital, for instance added to by education. W hile new growth theories (Romer, 1986) are intended to rectify these problems, they are rather mechanical and do not consider natural resources and the natural environment as possible constraints on economic growth. Thus they reflect optimism about technological progress and the ability of man
made capital to substitute effectively for declines in available natural resources. They therefore, contrast in their emphasis with the approach of neo-Malthusians and that of most ecological economists.2
For example, the above approaches are at odds with the theory of economic development as espoused by Georgescu-Roegen (1971, 1974) in which he emphasises the entropy of resources as a result of economic growth, and the views of Daly (1980) and Boulding (1966) who stress the interdependence of economic activity with the biosphere and the possible influences of this on economic production and human welfare.
The basic position of most ecological economists is that it is no longer tenable to study the growth of the economic system independently of the natural environment. The circular flow of economies needs to be linked to the natural environment in the way indicated in Figure 2. The natural environment acts as a receptor of wastes from the economic sector and as a source of inputs and a provider of goods and services for it.
Economic growth has an impact on these relationships, e.g., increased wastes from economic activity may reduce the quality of natural resources and so reduce economic production or welfare.
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Figure 2: Economic links with the natural environment.
Not only does neoclassical economic growth theory fail to take a holistic view along the lines illustrated by Figure 2, but it also relies on dubious assumptions about the nature of resources and resource availability. It fails to emphasise that the production of man-made capital always involves some transformation of natural capital (environmental resources and land) and that this transformation is as a rule irreversible. Of course, labour is also essential to this process. Man-made capital (the produced
means of further production) consists of man-made physical capital (machines, infrastructure and so on), human capital, (education, knowledge) and social capital (forms of governance, institutions, and cultural capital). These relationships are highlighted in Figure 3.
TOTAL CAPITAL STOCK =
Man-made Capital
Human Capital K n o t edge Education M sn-tn*de
Physical Capital
Social Capital e.j. Governance, Institutions
Labour
Natural Capital:
Environmental Resources, Land
Production o f Economic Goods and Services
+
Figure 3 : Production of man-made capital usually draws on natural capital and makes use of human capital, social capital, land and labour. Man-made capital is subject to depreciation, but natural capital is not usually. Even for human capital and social capital can depreciate.
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All man-made capital is subject to depreciation and therefore declines in availability in the absence of offsetting compensations. Hence, the Physiocrats may well have been correct in emphasising the fundamental importance of land (natural resource) for the sustainability of economic systems. It may come as a surprise that I also suggest that the maintenance of human capital requires continual investment. Knowledge in books and other media, for instance, needs to be maintained and it can only be used productively if every succeeding generation is trained in ways which enable them to use it. Thus continuous investment is required just to maintain human capital.
4. Capital Substitution and Sustainability
If the income of future generations is to be sustained, what assets should be made available to future generations? More generally, what combination of assets is needed to achieve it? These questions have been the subject of considerable debate.
It is convenient to distinguish between man-made capital and natural resource/environmental capital (Pearce, 1993). Man-made capital consists of produced physical capital (e.g., machines), human capital (e.g., the stock of knowledge) and institutional/cultural capital. Natural resource/environmental capital consists of renewable resources, non
renewable resources and flow resources. All these resources, together with labour, are determinants of economic production and welfare and their combinations affect the level of production and its sustainability.
The main debate that has emerged is the extent to which man-made capital can be substituted for natural resource capital and income be sustained or a desirable economic development path achieved.
Substitution of man-made physical capital for natural resource capital has been the focus of particular concern but also substitution within these categories is of interest.
Those economists who favour weak conditions for sustainability see the substitution of man-made capital for natural resource stock as a suitable
means for sustaining the income of future generations or for achieving a desirable development path from an anthropocentric viewpoint. By contrast, those favouring strong conditions for sustainability fear that given the extent to which the natural resource stock has already been depleted for consumption purposes and for investment in man-made capital, further substitution is liable to imperil the income or welfare of future generations.
It is argued that man-made physical capital is a wasting asset3, natural resource stocks are essential to its production and environmental capital plays an important complementary role in production. Because of the latter aspect, high levels of man-made capital relative to the environmental stock, can result in falling production.4 The main issues can be illustrated by taking a simplified case.
Suppose just two forms of capital: K, man-made capital, and N, natural resource/ environmental capital. Suppose that the income possibilities for future generations are a function of the ratio of man-made capital to natural resource/environmental stocks, engineered by present generations and inherited from previous generations, that is a function of K/N - the initial ratio of man-made capital to natural resource stock.
For each value of K/N, a large number of income possibilities for future generations exist. Select the preferred one for each value of K/N and suppose that all the preferred paths corresponding to each value of K/N can be ranked by preference so that a transitive and complete preference ordering exists. This can be used to generate an ordinal preference function such as ABCDF in Figure 4. There corresponds to each point on this curve an attainable income path (at least one) which gives the utility rank indicated. In some cases, the utility index may be of a von Neumann and Morgenstern type or cardinal, in which case expected utilities could be calculated, but it is not necessary to assume this here. Given the curve ABF indicated in Figure 4, a ratio of man-made capital to natural resource stock of Ri is optimal, that is maximises the objective or utility function under consideration5.
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Initial ratio o f man-made capital to natural resource/
environmental stock.
Figure 4: Diagram to explain anthropocentric reasons for imposing strong and weak conditions on substitution o f capital.
This diagram may help to distinguish between reasons for support of weak and strong conditions for sustainability. Those favouring weak conditions may believe that the economy is in the neighbourhood of B. If so, then K/N = Ro is too low to achieve the desired income possibilities for the various generations. On the other hand, those favouring strong sustainability conditions may believe the economy to be in the neighbourhood of a point like D. If so, the ratio of man-made capital to natural resource stock is already too high and any further transformation will make the situation worse. Some members of this group may also believe that the economy is in the neighbourhood of C, in which case further transformation would be liable to lead to a sub-optimal result.
The question of technological progress has not been mentioned. Ideally the type of relationships shown in Figure 4 should be drawn up allowing for future technological progress. In principle, this is possible. But in
practice, given fundamental uncertainty about future technological progress, it is only a theoretical possibility. After allowing for technological progress, a single peaked curve like ACF might still apply. However, super-optimists might consider a curve like AGH to be more relevant. If so, they would favour weak sustainability conditions strongly
5. Further Observations on Weak and Strong Conditions for Capital Substitution
One possibility not specifically discussed above is the possibility of discontinuities in the curves shown in Figure 4. For example, at some ratio of K/N, curve ACF may decline abruptly. If this is so, but the exact ratio at which it occurs is uncertain, one might expect it to result in precautionary behaviour, that is making sure that K/N does not reach the threshold in question. Discontinuities in the curves raise new policy possibilities.
Those with an ecocentric-bent (e.g., Leopold, 1979) are likely to favour a lower value of K/N than would be chosen purely on anthropocentric grounds, given that the conversion of natural resource/environmental capital to man-made capital reduces biodiversity (Swanson, 1994). Thus given curve ACF in Figure 4, this group would be expected to prefer point B to C and certainly C to D. Such conservationists vigorously support the imposition of strong conditions on the substitution of man-made capital for natural resource stock on ethical grounds.
Pearce (1993) points out that there is a spectrum of views about the extent to which weak or strong conditions should be imposed to achieve sustainable development. He summarises these in a diagram similar to that shown in Figure 5. However, this seems to allow only for the anthropencentric viewpoint. There may also be ‘dark green’
conservationists who wish to impose very strong conditions on substitution of man-made capital for natural capital to take care of other species even if this is at the expense of present and future generations of human beings.
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WEAK CONDITIONS FOR SUSTAINABILITY
• Man-made capital is a suitable bequest for future generations.
• Acceptable substitute man-made capital for natural resources.
• Desirable, however, to develop energy supplies from sustainable sources, such as solar, non-renewable energy resources are depleted.
STRONG CONDITIONS FOR SUSTAINABILITY
• Sress is on trying to hold the natural resource stock constant. Only limited sustitutability o f man-made capital for natural resources is allowed. This is said to be necessary to take care o f future generations.
A SPECTRUM OF VIEWS ABOUT CONDITIONS FOR SUSTAINABILITY
• Very W eak • W eak • In term ed iate • Strong • Very Strong i
Growth (
k
▲
Optimist ‘Dark Green’
Conservationists
Figure 5 ? Weak and strong conditions for sustainable development and spectrum o f about these conditions according to Pearce (1993, Ch.2).
Simonis (1990, p. 11) mentions the need for a new symbiosis between Man and Nature if sustainable development is to be achieved. What is not clear is whether he is advocating this new symbiosis or harmony between society and nature from an anthropencentric viewpoint or whether his standpoint also includes an independent concern for nature as such. In any case, it is clear that he does not advocate a ‘dark green’ position because he states: ‘First of all, the postulate to sustain development processes, must not lead to a rigid standpoint, like ‘keep hands off nature’
(Simonis, 1990, p. 11), so he may be taking an intermediate stance.
The question might also be raised of whether the optimal ratio of man
made capital to natural resource stock could differ between societies. This is indeed possible. For one thing, the natural resource endowment of countries differ. Hence, curves like the one shown by ACF in Figure 4 may differ between countries. Thus the optimal value of K/N may, for example, differ between China and Europe. The optimal value for China might be lower than for Europe. Nevertheless, the current K/N value for China may be less than its optimal whereas that for Europe might be in the neighbourhood of its optimum, given the different histories involved.
Those supporting strong conditions for sustainability often favour offset policies. This means that a development which destroys the natural environment might be allowed if it is offset by an initiative elsewhere which improves the natural environment. For example, the destruction of a natural wetland for a housing development may be allowed if an artificial wetland is established elsewhere. However, if this artificial wetland is established in an existing natural environment, it will destroy it. In this case, the natural environment, rather than remaining constant, is changed in its composition and there is arguably some reduction in the natural resource stock. The question of what is a suitable environmental offset for deterioration of the natural environment in some respect can be contentious. In some cases there may be little contention, e.g., in cases where land degraded by economic use is restored to a more natural state, and used as an offset for use of a natural environment of little value elsewhere.
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6. Concluding Comments
There are rational reasons, even given that our goal should solely be to benefit humanity, for believing that the standard economic objective for sustainable development is not always socially desirable. This is so taking into account Rawls’ principle of justice. Nevertheless, this is not at odds with account being taken of the welfare of future generations of human beings. It still may require strong conditions to be imposed on the substitution of man-made capital for natural resource/environmental capital. This has been illustrated diagrammatically, and a diagram has been used to help clarify the differences in views about whether strong or weak conditions should be imposed on the substitution of man-made capital for natural resource/environmental stocks.
Endnotes
1. Observe that the curve or path which has the maximum area under it will also yield the maximum expected value of income per unit of time or for each generation, if generations are equally spaced in time. The area under the curve being considered can be found by integration. If the time interval 0 < t < t„ is divided into n equal ‘periods’ each corresponding to a generation, then expected income for an individual as yet unborn can be found by dividing the area under the relevant curve by n. I am grateful to Christopher Tisdell for his suggestion about this mathematical point.
2. The contrast between these views is higlighted in a recent issue of Ecological Economics (Vol. 22, No.3, 1997) in honour of Georgescu- Roegen in which Daly and Solow, in conjunction with Stiglitz, are the main adversaries.
3. Hartwick (1977) in support of neoclassical growth theory, envisages sustainable levels of consumption being achieved by investment that offsets this wasting. The problem, however, as previously pointed out by Ströbele (1984) and Muller and Ströbele (1985), is that this further depletes the level of natural capital stock. Hence, it is not a means to achieve long-term sustainability.
4. Research at the Wuppertal Institute and elsewhere (World Resources Institute et al. , 1997) indicates that material throughput both absolutely and per capita continues to rise gobally and thus the level of the natural resource stock continues to diminish. This rise in per capita levels of throughput is even occuring in more developed countries.
5. What is being assumed here is that an appropriate balance between natural resources and man-made capital is needed to maintain production and utility. This is an application of the Law of Variable Proportions.
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