Final answer:
Slash and burn agriculture is limited by poor soil fertility, the need for land to regain fertility through fallow periods, and the unsustainability caused by overpopulation leading to deforestation and soil degradation.
Step-by-step explanation:
What factors limit slash and burn agriculture? The efficiency of this method is primarily constrained when the population relying on it becomes too large. Slash and burn is sustainable in regions with small populations and where it is practiced in rainforest climates with poor soils that are otherwise infertile. Nutrients are added to the soil through burning vegetation, but this fertility is temporary. Rain leaching away soil nutrients and the need for land to lie fallow to regain fertility are additional limiting factors. Overpopulation can lead to the unsustainability of this practice, as it puts excessive pressure on the land, leading to deforestation and soil degradation. In contrast, agricultural practices in some developing countries have been adapted to local conditions and are highly efficient even on difficult terrains.