Published online by Cambridge University Press: 22 May 2009
The vast majority of the decisions made in our global society are responses to problems in which cause and effect are closely related in time and in space. When a problem becomes important, its source is usually obvious, and any appropriate response usually becomes effective in time to eliminate the difficulty. For this class of phenomena it is satisfactory to react after a problem is already apparent. Thus, the institutions involved need only monitor the current status of the system; they need not maintain a long planning horizon. It is important to realize that most environmental problems do not fit into this category. The delays associated with most environmental processes will require us to add an explicit consideration of the time dimension in formulating environmental policy.
1 An excellent example is provided by the attempts to alleviate air pollution in the United States. Although new technologies have been developed and new laws have been enacted to drastically reduce the amount of pollution emitted by many sources, population and production are growing rapidly enough that total air pollution continues to worsen. (See Environmental Quality: The Second Annual Report of the Council on Environmental Quality, together with the Message of the President to the Congress [Washington: Government Printing Office, 08 1971], pp. 212–217.)Google Scholar
2 The system dynamics methodology was developed by Jay W. Forrester of the Massachusetts Institute of Technology during his study of corporate problems. The field is widely known as industrial dynamics, after Forrester's book by that name, but the title is no longer appropriate. Fourteen books and over 100 articles published by the System Dynamics Group at MIT have illustrated the application of the approach to problems including internal body disease, urban decay, commodity price fluctuations, and population growth in traditional societies. The basic elements of the approach are described in Forrester, Jay W., Industrial Dynamics (Cambridge, Mass: M.I.T. Press, 1961);Google Scholar by the same author, Principles of Systems (Cambridge, Mass: Wright-Allen Press, 1969);Google Scholar and Pugh, A. L., DYNAMO II User's Manual (Cambridge, Mass: M.I.T. Press, 1970).Google Scholar
3 Randers, Jorgen and Meadows, Dennis, “System Simulation to Test Environmental Policy: A Sample Study of DDT Movement in the Environment” (Unpublished working paper, System Dynamics Group, Alfred P. Sloan School of Management, MIT, Cambridge, Mass., 1971).Google Scholar
4 The most serious uncertainty does not involve the various paths of DDT movement but rather the biological implications of its presence at various concentrations in different species. That important issue does not concern us in this analysis of DDT transmission delays though it is important in evaluating the relative costs and benefits of alternative policies.
5 Harrison, H. L. et al. , “Systems Studies of DDT Transport,” Science, 10 30, 1970 (Vol. 170, No. 3957), pp. 503–508;Google ScholarWoodwell, G. M. et al. , “DDT in the Biosphere: Where Does It Go?,” Science, 12 10, 1971, (Vol. 174, No. 4014), pp. 1101–1110.Google Scholar
6 Randers, Jorgen, “The Dynamics of Solid Waste Generation” (Unpublished working paper, System Dynamics Group, Alfred P. Sloan School of Management, MIT, Cambridge, Mass., 1971).Google Scholar An abridged version of the paper is presented in Technology Review, April 1972 (forthcoming).
7 Anderson, A. A. and Anderson, J. M., “System Simulation to Test Environmental Policy III: The Global Distribution of Mercury” (Unpublished working paper, System Dynamics Group, Alfred P. Sloan School of Management, MIT, Cambridge, Mass., 1972);Google Scholar and Anderson, J. M., “System Simulation to Test Environmental Policy III: The Eutrophication of Lakes” (Unpublished working paper, System Dynamics Group, Alfred P. Sloan School of Management, MIT, Cambridge, Mass., 1972).Google Scholar