The brown locust is endemic to the semi-arid regions of South Africa and southern Namibia, posing a threat to food security as far north as Zambia. Outbreaks occur – over roughly 24 million hectares of the Karoo – when good breeding conditions result in a dramatic increase in the density of scattered, solitary adult locusts. Previous studies have shown that there is a strong correlation between the scale and extent of outbreaks and early summer rainfall. A CPP project is helping to develop a brown locust early warning system (BLEWS). The distribution of outbreaks has been examined, using historical records of brown locust occurrence collected since the start of the twentieth century together with environmental data for the same period.