This paper analyzes the dynamics of population growth and urban expansion in the city of Xalapa, Mexico. It focuses on the establishment of informal settlements, which are one of the many threats to forest and farmland conservation (although these settlements are not the only source of the problem). Spatial analysis of growth data (using Geographical Information Systems (GIS) and statistical modelling) showed that by 2007, 90 per cent of the land area in the municipality of Xalapa had already been altered by human activity.