Introduction: Lakeland

There are other renewable resources than soil such as water, fish and forest produce. Let us make a trip to the imaginary country Lakeland to illustrate the nexus between population and resource exploitation. The country consists of two subsystems: a lake or coastal area with fish and their food – say, daphnia, a kind of water flea – and the economy of people, fishing boats and a reserve of mineral ore with high gold content (Figure 12.1). The Lakelanders get their food from fishing in the local lake and make their boats and nets from local materials. There are only two capital stocks: boats and nets, and mining equipment. They change because of investment and depreciation, with the latter assumed to be inversely proportional to the economic lifetime. The demand for fish is growing over time because of population growth. This means more boats and nets. Therefore, you can make three reasonable assumptions about the fishermen behaviour and the ecosystem:

• fishermen invest in new boats and nets in order to satisfy expected growing demand;

• there is an upper bound to the annual fish catch; and

• gold mining causes pollution, which negatively affects the daphnia.

Each season the fishermen go out harvesting fish, which is sold on the local market at the end of the season. Assuming a population growth of 1 percent per year (%/yr), the Lakeland fishing grounds are sustainably exploited over the chosen simulation period of about twenty years (1,100 weeks; Figure 12.2a). As long as the population and fish demand hardly change, the fleet size remains about constant. Such a sustainable state has existed in many places and for long periods, with different institutional arrangements. Note that the model is meant to be an illustration and has not been implemented for a real-world situation.