Operattonaiizing Sustainable Development : Dynamic Economic - Ecological Models . '

Since the mid-eighties, a vast literature has evolved around the concept of sustainable development. It shows a wide support for changes in policy-making and decision-making, for instance, to integrate environmental interests in national and international political processes. Remarkably, recommendations of contours and new elements of research methods and policy analysis for sustainable development are rare, although this is just as essential as the renewed attention for the political dimension. A clear view on how to use and change adequately existing techniques and models for sustainable development will contribute to a more satisfactory operationalization of it. This paper examines the implications of ecologically sustainable economie development for integrated dynamic modelling. After a concise discussion of sustainable development it is suggested that five concepts are central to it: intergenerational equity, the regional scale, multiple use, long term unceitainty, and economic-ecological integration. The discussion of each of these issues is focused on the implications for model elements and uses. Thereby, old ideas are reviewed and new ones are proposed. The aim is not to come up with a rigid framework for dealing with sustainable development but rather to suggest which alternatives are available to deal with the central concepts, although in a section on economic-ecological integration general requirements for dynamic economic-ecological models are mentioned explicitly in order to offer a general frame of reference. These requirements are fairly general and may be taken up in ensuing discussions of the methodological aspects related to sustainable development. The main condusions are the following. We view economicecological integration in the sense of combining processes instead of one process and a variable. To deal with intergenerational equity one may choose objectives, various constraints, or a combination of botb, For regional models one may consider various types of conditions on cross-boundary flows and external factors of regional processes. Multiple use can be modelled as an intermediate stage between single resource models with a partial view and complex models with a general view. Sensitivity, probability and scenario analyses can be used to deal partially with the various types of long term uncertainty, although this remains