1999-2003 (NSF 9817743, #0138217) PI (Mamadou Baro, Gary Christopherson and Stuart Marsh co-PIs) on a grant “Creation of a GIS for six Cities in Arid Environments: in Morocco, Senegal, Mali, Niger, Tanzania, and Botswana.” funded by NSF ($499,735) to build a broad picture of urbanization in Africa and its impact on the natural resources of urban hinterlands through the use of remote sensing imagery and, at a later stage, urban research focussing on the poorer segments of six cities (Marrakech, Dakar, Bamako, Niamey, Dodoma and Gaborone). We are developing a diachronic picture of change in urban features such as garbage dumps, shanty towns, built up urban areas, market gardens etc that will allow one to hypothesize about the differential impact on the environment of demographic trends among the rich and poor or business and government urban sectors. A key finding was that a remote sensing diachronic sampling technique based on past and current housing form produces urban classes which are homogeneus in terms of a wide variety of socio-economic indicators while a similar set of classes based only on current housing form are vastly less socio-economically homogeneous.