Thinking in Systems
In a physical exponentially growing system, there will always be one reinforcing loop driving the growth and at least on balancing loop constraining the growth. This ensures that no system grows forever.
In a two stock system, as the resource become more scarce, it becomes harder to obtain and therefore rises in price.
Two stock systems can depend on two types of resources: non-renewable, and renewable.
Systems that depend on a non-renewable resources will reach and end of the stock and therefore the system. The only thing that can be controlled in this type of system is the amount of time the stock will last.
The amount of the resource makes little difference if the growth is exponential.
To control how long the stock lasts, the extraction rate must be closely controlled. The faster the extraction rate grows and higher it gets, the more capital the stock will produce, but the shorter life it will have.
Systems that depend on renewable resources can provide resources indefinitely, but require a delicate balancing act.
If the system has a strong balancing loop and low technological advances, they can reach a point of balance with the renewable resource.
If the system has a weaker balancing loop, or technological advances allow further resource extraction without a cost increase. Then, the system will never reach an even balance. Instead, it will oscillate around the ideal balance point.
A renewable resource can also turn non-renewable if the balancing loop is too weak. In this case, the reinforcing regenerating loop of the resource becomes dominated by the balancing loop of extraction and the resource stock starts declining into extinction.