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Journal Articles

Managing the resilience of lakes: a multi-agent modeling approach

Janssen, M.A. and S.R. Carpenter

1999 Conservation Ecology 3(2): 15.


We demonstrate an approach for integrating social and ecological models to study ecosystem management strategies. We focus on the management of lake eutrophication. A model has been developed in which the dynamics of the lake, the learning dynamics of society, and the interactions between ecology and society are included. Analyses with the model show that active learning is important to retain the resilience of lakes. Although very low levels of phosphorus in the water will not be reached, active learning reduce the chance of catastrophic high phosphorus levels.

Keywords: active learning, eutrophication, integrated modeling, lake dynamics, lake management, multi-agent modeling, phosphorus, resilience, restoration, simulation.


Perspectives on global energy futures: simulations with the TIME model

Vries, H.J.M. de, M.A. Janssen and A. Beusen

1999 Energy Policy 27(8): 477-494.


Many uncertainties and controversies surround the future of the global energy system. The Targets Image Energy (TIME) model of which a concise description is given, is used to explore the consequences of divergent assumptions about some uncertain and controversial issues. The IPCC-IS92a Conventional Wisdom scenario is used as a reference and, in combination with two other scenarios, discussed in the context of other recently published global energy scenarios.

Keywords: Global energy scenarios; Energy modelling; Climate change.


An integrated approach to simulating behavioural processes: a case study of the lock-in of consumption patterns

Janssen, M.A. and W. Jager

1999 Journal of Artificial Societies and Social Simulation 2(2).


Lock-in denotes a phenomenon of monopolistic dominating technologies or consumer goods in a certain market. These lock-ins cannot be explained by superior characteristics of the good or technology. Previous studies mainly used probabilistic models to study lock-in effects. In this paper an integrated conceptual model of consumer behaviour is used to identify relevant processes of lock-in dynamics of consumption patterns. An agent-based model is developed to simulate consumats, artificial consumers, who are confronted with two similar products. We found two types of lock-in, namely, a spatial lock-in and a global level lock-in. The spatial lock-in related to the spatial patterns that occur in consumption patterns and relates to the satisfaction of the need for identity. The global lock-in relates to price effects and occurs only if individual preferences are not significantly weighted in the cognitive processing.

Keywords: Lock-in, multi-agent modelling, social psychology, need satisfaction, consumer behavior.


Book Chapters

An evolutionary integrated modelling approach: a case study for climate change

Janssen, M.A.

1999 In Complex Problem Solving: Methodological Support for Societal Policy Making, edited by D.J. DeTombe & E.A. Stuhler, pp. 130-139,  Rainer Hampp Verlag, Munchen u. Mering.


Addressing global change demands an integrative consideration of interactions between humans and the environment on a world wide scale. An assimilative integrated system approach seems to be appropriate for investigation of this complex global problem. In this paper an integrated modeling approach is proposed that is based on an evolutionary view on global change. A case study is worked out where images of the future using a multi-agent model are assessed, and where agents differ in their world view and thus also in their preferred management style. The perspective of agents may change due to new information they derive from the system. A simple model is constructed to illustrate the consequences of this approach on climate change scenarios.


Global modelling: managing uncertainty, complexity and incomplete information

Janssen, M.A. and H.J.M. de Vries

1999 In Validation of Simulation Models, edited by  Cor van Dijkum, Dorien DeTombe and Etzel van Kuijk, pp. 45-69, Amsterdam: SISWO.


Human activities change the environment on a global level. Global modelling is used to derive insights in the interactions between humans and their environment. However, the possibility to validate those global models is limited. In fact, too little information is available, many subjective assumptions are made and a single model cannot cover all relevant scale levels and processes. These limitations already appeared in the early seventies. Current global modelling activities still deal with the same dilemma’s, often in the same way as the strongly criticised world models of the early seventies. We sketch some recent developments which can help to manage the persistent dilemma’s. We focus on the use of different modelling paradigms and on the use of different world views to analyse the consequences of subjective assumptions to be made in global models.

Keywords: global modelling, validation, complexity, uncertainty.


Book Reviews

Ford, A. (1999). Modeling the Environment: An Introduction to System Dynamics Modeling of Environmental Systems. Island Press. Washington, DC

Janssen, M.A.
1999 Ecological Economics 31(3); 464-465.


Consumats in a commons dilemma. Testing the behavioural rules of simulated consumers

Jager, W., Janssen, M.A., Vlek, C.A.J.
1999 COV report no. 99-01. Groningen: Centre for Environment and Traffic Psychology, University of Groningen.


In this paper we report on a series of computer simulation experiments on the management of a common resource. We were particularly interested in the effects of uncertainty and satisfaction on the harvesting behaviour of simulated agents. Because the experimental study of the long-term dynamics of resources that are being depleted to a serious extend can hardly be done using real human subjects, we experimented with simulated consumers. These simulated consumers, or ‘consumats’, have been developed using a multi-theoretical framework integrating various theories that appear to be relevant in understanding consumer behaviour. The consumat is equipped with needs and abilities, and may engage in different cognitive processes, such as deliberating, social comparison, imitation, and repeating previous behaviour. In a first series of experiments we tested these cognitive processes on their functioning. In a later series we experimented with the consumat attributes and the resource characteristics. It was found that an increased uncertainty resulted in an increased ‘optimism’ of consumats regarding future outcomes, an increased likelihood of imitative behaviour, and a lesser adaptation during resource depletion. These ‘process-effects’ caused higher uncertainty resulting in higher levels of harvesting, an effect that has been demonstrated previously in experiments with real human subjects. The paper concludes with a discussion on the ecological validity of the simulation results.


SIMBIOSES-Modelling industrial metabolism in a regionalised economic system

Janssen, M.A. and J.C.J.M van den Bergh
1999 Tinbergen Institute discussion paper, TI 99-060/3.


A model framework, SIMBIOSES, is presented which describes economic activities and related material, substance and energy flows in a multi-region and multi-sector economic system. The conceptual design of the framework is discussed in relation to current issues on “dematerialization” and “decoupling”.

Three types of models to implement SIMBIOSES are discussed: a static equilibrium model, a dynamic optimisation model, and a system dynamics model. The static model determines the static equilibrium of extraction, production, recycling, and energy recovery from waste. The dynamic model determines the long-term investment decision that optimises total discounted utility of consumption. The dynamic model incorporates technological change, allocation of resources, and damage costs due to accumulation of substances in the environment. The system dynamic model generates endogenous economic growth and technology development and includes bounded rationality of economic agents.

Keywords: dematerialization, mass balance, integrated models, Environmental Kuznets curve, equilibrium analysis, dynamic optimisation, system dynamics.


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