The traditional agricultural system of semi-nomadic people, in which a small area of forest is cleared by burning, cultivated for 1–5 years, and then abandoned as soil fertility and crop yields fall and weeds encroach. Ideally vegetation succession subsequently returns the plot to climax woodland, and soil fertility is gradually restored. Shifting cultivation of this type was once practised worldwide but in modern times it has been primarily associated with tropical rain-forest areas. The system is best suited to low population densities. With increasing population pressure, abandoned plots are often cleared again before a full climax community has been restored, leading eventually to nutrient depletion of the system and degradation of forest to open savannah-type woodland or scrub.