Final answer:
Slash-and-burn agriculture can become unsustainable with increased population growth due to heightened demand for land and resources, despite its historical efficiency in small population scenarios.
Step-by-step explanation:
The statement 'Slash and burn agriculture remains efficient only as long as the population and the amount of land available remain constant' is false. Slash-and-burn farming has been sustainable in areas where the population remains small and can produce a crop with minimal labor and effort. However, this farming method faces challenges when population growth leads to increased demands for land, food, water, and energy, leading to habitat destruction and potentially unsustainable practices. In regions with poor soils and harsh climates, variations of slash and burn known as Inga Alley Cropping have been suggested as alternative methods that can preserve forest cultures and maintain ecological sustainability over the long term.