Bush encroachment affects the agricultural productivity and biodiversity of 10-20 million ha of South Africa. Many people believe that we understand the causes of bush encroachment. We do not. Many people believe that either fire or heavy grazing by domestic livestock is the sole cause of bush encroachment. This is wrong. Bush encroachment occurs in many arid regions where fuel loads are insufficient for fires to be an important causal factor. Keywords: disturbance, fire, grazing, plant-herbivore interactions, rangeland, shrub encroachment.