The Agricultural and Persistent Pollution Subsystems in World3

The agricultural and persistent pollution sectors of the Club of Rome´s World3 model are analyzed to obtain a better understanding of their inner workings, and to show how such understanding may be acquired step by step, using simple methods of systems and control engineering. Only few of the agricultural sector´s equations essentially affect standard-run behavior. Food production is mainly determined by industrial output (exogenous to the sector) and arable land, and is virtually independent of population and pollution. Except for the arable land subsector, the agricultural sector is found to act more or less algebraically. If pollution rises considerably above its standard-run values, however, the sector´s properties may be quite different. The persistent pollution sector is found to be fairly inactive for standard-run conditions, but, owing to a particular assumption on its absorption, pollution may suddenly rise to high levels under different conditions and therefore have an important impact on food production and population.