Final answer:
Before the intrusion of outsiders, the economies of low islands were based on fishing, crop cultivation, and trade with nearby islands.
Step-by-step explanation:
The economies of low islands before the intrusion of outsiders were traditionally based on fishing, growing crops, and trade with nearby islands. Fishing has been one of the main economic activities, providing food for the local population and resources for trade. In some cases, tourism and the export of natural resources such as minerals and fossil fuels have also contributed to the economy of certain islands.