Dynamics of Built-Up Areas and Loss of Vegetation in Secondary Towns: Case Study of Sarh Town in Chad, Central Africa

The expansion of secondary towns in Africa, although less rapid than that of capital cities, poses significant challenges for environmental sustainability. Sarh town (Chad) is an example of this urbanisation phenomenon, which has led to a significant loss of vegetation. This research aims to analyse the dynamics of land use, focusing on the expansion of built-up areas and the loss of vegetation. The methodology used includes the analysis of Landsat images from 1994, 2003, 2013 and 2022, supplemented by field data, statistical analysis, interviews and documentary analysis. The results show that the built-up area, estimated at 806 hectares in 1994, reached 2,603 hectares in 2022, representing an annual increase of 4.1%. Moreover, the area of vegetation decreased from 759 hectares to 231 hectares, a reduction of 69%. In addition, there is a strong negative correlation (r = ̵ 0.93) between the expansion of built-up areas and the loss of vegetation. On average, the annual growth of built-up areas (4.1%) exceeds that of the population (3.33%). Field surveys reveal that this situation is due to a preference for more spacious housing, inadequate land management and limited resources for vegetation rehabilitation. These results highlight the need to adopt effective planning tools to ensure sustainable land use.