More on resilience and sustainability as an indicator of carrying capacity

g¦B0, U is shown by the curve marked HJKLM. J represents the maximum individual utility and occurs at a population size of N 2 . Beyond this point social utility keeps on rising up to a point N 3 if the set of social welfare functions repre- sented by W B apply. However, if the set of social welfare functions W A indicated in Fig. 4 apply, social utility will rise until population reaches N 4 . The socially optimal population size ‘social car- rying capacity’ is therefore determined by the chosen social welfare contours W A , W B , and so on. As Fig. 4 indicates, carrying capacities de- pend on normatively based social welfare func- tions see also Tisdell, 1990, p. 160. If higher welfare contours as those indicated in Fig. 4 were chosen this would mean that the carrying capacity will be transgressed. Discussions of welfare economics indicate that the welfare curve of Bergson-type cannot be es- tablished objectively by adding up individual utili- ties Rothschild, 1993, p. 71. Other approaches seem necessary to bring population number and human welfare into a relationship which is so- cially acceptable for present and future generations. One attempt to approach social welfare func- tions is to make use of ideas and expressions of society about how to live and what to aim for. This can provide an image of social carrying capacity, making this concept more concrete. Au- thors like Daily and Ehrlich 1992, p. 763 fall back on normative concepts which focus on con- ditions of the environment by calling upon sus- tainability and environmental standards. They stress the following connection: ‘‘A sustainable process is one that can be maintained without interruption, weakening, or loss of valued qualities. Sustainability is a nec- essary and sufficient condition for a population to be at or below any carrying capacity.’’ This definition of sustainability represents an equilibrium state like the concept of carrying ca- pacity in applied ecology does. Furthermore, in order to determine the level of maximal sustain- able use of resources Daily and Ehrlich 1992, p. 765 introduce the idea of a limit or threshold ‘below which the constituent stocks are so small that the resource cannot be used sustainably’. Yet, sustainability requirements and acceptable stan- dards are influenced by human choices. Thus, it has become clear that applications of the concept of carrying capacity to problems induced by hu- mans leads to a shift from a positivist-type con- cept to a normative one. This shift means that there is no longer an objective, single level of carrying capacity equilibrium population as in the blowfly experiment. Rather it is replaced by different more or less stable states of environment dependent on value-judgements, institutional ar- rangements, technologies, consumption patterns, and human aims. These factors must be concili- ated, be agreed upon and considered for estimat- ing the acceptable pressure on the environment, and for developing accompanying management schemes. Therefore, political and social ideas and norms about technologies, institutions, consump- tion, distribution etc. have to be discussed, har- monized and agreed upon to approach a stable quality of the environment equilibrium situa- tion. If discrepancies become visible, in other words, if human activities will not stay within the carrying capacity, society will have to discuss its values, develop its technologies and institutions, and review its aims.

5. More on resilience and sustainability as an indicator of carrying capacity

One of the most recent developments of the concept of carrying capacity has been to relate it to ecological resilience Arrow et al., 1995. How- ever, some writers making this connection, such as Arrow et al., do not see carrying capacities as particular critical limits, but rather as normative, variable concepts which accord with the view given above. Arrow et al., 1995, p. 521 state: ‘‘Carrying capacities in nature are not fixed, static, or simple relations. They are contingent on technology, preferences, and the structures of production and consumption. They are also contingent on the ever-changing state of inter- actions between the physical and biotic environ- ments. A single number for human carrying capacity would be meaningless because the con- sequences of human innovation and biological evolution are inherently unknowable.’’ Thus, it is clear that these writers reject particu- lar critical limits but they indicate that carrying capacity has been exceeded when ecosystem re- silience is lost and a system flips from one locally stable equilibrium to another because the ecosys- tem is so altered that its resilience in relation to its original equilibrium is overcome. Despite the above, suggestions can be found in the literature that the concept of carrying capacity is more definite than in Arrow et al. 1995, even when it is related to resilience. For example, Per- rings et al. 1995 suggest that there are critical points at which ecosystems will collapse and have most ‘unwelcome’ economic consequences for the human population. They state: ‘‘The notions of ‘carrying’ and ‘assimilative’ capacity are indirect measures of the level of stress that is consistent with a tolerable level of resilience what level of resilience is tolerable depends on the severity and frequency of the ‘shocks’ expected to occur. Since, for a given technology, human population growth implies an increasing level of stress on the ecosystems exploited under that technology, there is neces- sarily some point at which the associated loss of ecosystem resilience will become critical. Hu- man population growth will at some point cause the collapse of those ecosystems.’’ Per- rings et al., 1995, p. 8. This view, however, raises many questions. What is a tolerable level of resilience? Does not a decision about what is tolerable involve a value- judgment, and how will social agreement be reached about such judgments? What does it mean to say the loss of ecosystem resilience will become critical? Critical in what way, or from what point of view? Does critical imply a jump or discontinuity in the system? Is there likely to be a continuous reduction in ‘utility’ rather than a precipitous decline in it as some ecosystems ‘col- lapse’? What does it mean to say that an ecosys- tem collapses? Do they collapse or merely alter? Certainly many questions remain unanswered, even though the authors correctly stress the ability of human populations and activity to alter the nature of ecosystems and the natural environment.

6. Concluding comments: social carrying capacity and its application