The Carring Capacity Myth

by William Cheung

In a public forum "The Marine Environment of Hong Kong: Now and Beyond 2010" organized by the Hong Kong Marine Biological Association on 2 December 2000, one statement that was brought up in the discussion session was "…allowing disposal of waste into the sea, that is, within the carrying capacity of the ocean." The thing that stimulated my thinking was not on the issue of using the sea as our garbage bin, but more on the "carrying capacity" aspect. In fact, usage and exploitation of the sea within its carrying capacity has been a primary goal of marine conservation in the last century. However, I argue that "carrying capacity" is an unattainable and inappropriate goal of marine conservation. Alternatively, I propose that rebuilding or restoring our natural resources and environment to its past under-exploited state should be our new goal. In this article, I will focus the discussion on marine conservation issues, but I do not see any limit to expanding the same argument to the terrestrial side.

Carrying capacity is defined here as the level of use, at a given level of management, which a natural or man-made resource can sustain over long period of time (Scialabba, 1998). It seems that this is an attractive and plausible term. With the advocacy of "within the carrying capacity", people can unwarily exploit natural resources or dispose waste into the sea. However, before that, one must determine what is the carrying capacity of our environment. This will inevitably rely on the search for reference points which provide people with an indication of the limit of our natural environment. For instance, fishery scientists or managers put tremendous effort in determining reference points such as the Maximum Sustainable Yield (MSY) over the last century. In the past (and some still do believe that nowadays), they claimed that fishery exploitation within MSY can be sustained forever! Another example is the use of various Water Quality Objectives such as level of Biochemical Oxygen Demand, E. coli amount etc. in water to determine how much sewage we can dispose into the sea. These indicators are used to determine the "carrying capacity" of the sea.

I called "Carrying capacity" a myth because it can never be truly determined. The first reason is the inability of these reference points in indicating the actual carrying capacity of the ocean. In general, determination of reference points Requires baseline information of the environment, so that usage of natural resources within the specific reference point does not have a significant impact on the environment as per the baseline. However, if someone is able to compare the environmental "baseline" from previous generations to the present day one, it may be obvious that the "baseline" is shifting (and sadly most shifts are unidirectional to a lower standard baseline). For example, in the 70s, people swam every morning in the Victoria Harbour just outside North Point. Nowadays, the baseline of our Harbour is that it is only good for providing toilet flushing water. In my father’s generation, Tolo Harbour was a pristine coast with fringing corals, and I would say that my personal impression of Tolo Harbour is its polluted water. Similar shifts in baseline have also been widely documented in fisheries, in which each generation of fisheries scientists accepts as a baseline the stock size and species composition that occurred at the beginning of their careers, and uses this to evaluate changes. Pauly (1995) termed the phenomenon "Shifting Baseline Syndrome". With this shifting baseline, do you think that the carrying capacity of the ocean is also shifting? The answer is no. It merely reflects our inability in determining the true carrying capacity of our ocean.

The second reason for the "Carrying capacity" myth is the difficulty in the estimation of the specific reference point, even if no shift in baseline is assumed. Both the biotic and physical aspects of the marine environment are highly uncertain. For example, water current, upwelling, water temperature etc. can vary greatly in an event of El Niño. Recruitment in fish stocks is largely unpredictable. Since the true carrying capacity of the ocean is associated with highly varying environmental conditions, there is a large uncertainty in estimation of the specific reference point used to determine the carrying capacity. Even if the precautionary approach is applied, it is often difficult to arrive at a consensus between various stakeholders ( i. e. the government, conservationists, scientists and resource-users) for adopting a conservative reference point. Moreover, to determine the carrying capacity, one must over-load the system first so to identify the threshold. However, irreversible damage may have already been imposed on the environment before the realization that the carrying capacity has been over-reached. Again, these problems suggest that the determination of carrying capacity is both difficult and dangerous.

Owing to the inappropriateness of the "Carrying capacity" myth, it is suggested that rebuilding and restoring should be a new goal of marine conservation. This idea was initiated from Pitcher and Pauly (1998) who suggested the novel idea of rebuilding the past under-exploited ecosystem, rather than sustaining at the present level of misery, should be the ultimate goal for fishery management. This idea should also be suitable in marine conservation in general. It should be noted that there is no intention to bring our environment back to prehistory. Instead, we should target for a state where every users of the ocean, including organisms in the marine ecosystem, enjoy a justified share of the resources (Brunk and Dunham, 2000).

Sceptics say that costs (in terms of pure market value) will be too high to make the restoration/rebuilding goal realistic. Such conclusion was drawn because non-market values, which include social and ecological values, were not taken into account. The social and ecological values can be understood as the benefits obtained from people having a good environment, and the intrinsic value of the ecosystem respectively. Moreover, intergenerational equality must be considered, which means that our children and grandchildren should be able to see the sea and marine resources as valuable as we see nowadays. With cost-benefit evaluations including all of the above factors, it should be obvious that more benefits could be obtained from restoration/rebuilding. This has been shown quantitatively in fishery resources studies (Buchary et al., in prep; Sumaila et al, in press).

The restoration/rebuilding goal sounds theoretical, but it should not be viewed as a "Hanging Garden". To implement restoration/rebuilding of the marine environment, consensus must first be made between different stakeholders on what state of the marine environment should we target for. Then cost-benefit analyses of restoration should be carried out. After that, suitable measures or policies should be developed to facilitate restoration.

In conclusion, it has been argued that the target on the Carrying Capacity Myth is inappropriate for marine conservation. Effort should be redirected to restore/rebuild a healthy, under-exploited, marine environment. Standing on the shoulder of a giant, I just want to arouse more discussion to search for directions for marine conservation in the new millenium. The hope of swimming in Victoria Harbour without worrying about going to hospital because of intestinal infection, or fishing sizeable sea perch in Castle Peak Bay, as one of Mr. Peter Wong's wishes in a recent public forum, is always here.

Bibliography

Brunk, C. and S. Dunham. (2000). Ecosystem Justice in the Canadian Fisheries. Pp. 9-33. In H. Coward, R. Ommer and T. Pitcher (eds.). Just Fish: Ethics and Canadian Marine Fisheries. Institute of Social and Economic Research, Memorial University of Newfoundland, St. John.

Buchary, E.A., W.L. Cheung, U.R. Sumaila and T.J. Pitcher. in prep. Back to the Future: a paradigm shift for restoring Hong Kong marine ecosystem.

Pauly, D. (1995). Anecdotes and the shifting baseline syndrome of fisheries. Trends Ecol. Evo. (U.K.) 10:430.

Pitcher, T. J. and D. Pauly. (1998). Rebuilding ecosystems, not sustainability, as the proper goal of fishery management. pp. 311-329. In T. J. Pitcher, P. Hart and D. Pauly (eds.). Reinventing Fisheries Management. Kluwer Academic Publishers, London.

Scialabba N. (ed.) (1998). Integratred Coatal Area Management and Agriculture, Forestry and Fisheries. FAO Guidelines: 256 p.

Sumaila, U.R., T.J. Pitcher, N. Haggan and R. Jones. (2000). Evaluating the Benefits from Restored Ecosystems: A Back to the Future Approach. In R.S. Johnston and A.L. Shriver (eds.): Proceedings of the 10th International Conference of the International Institute of Fisheries, Economics and Trade. Corvallis, Oregon, USA (in press).

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