Facteurs de dégradation des peuplements d’acacias gommiers dans le département de Dourbali (Tchad)

Abstract

Natural resources in the Sahel region face increasing threats that compromise their sustainability and availability over time. The combined effects of anthropogenic and climatic pressures are jeopardizing the ecological balance and resilience of ecosystems in arid and semi-arid regions of Africa. This dissertation examines the factors driving the degradation of gum acacia stands in the Dourbali department, taking into account anthropogenic, institutional and climatic influences. Acacia gum stands play a crucial role in this local community, providing a socio-economic source, notably in the production of gum arabic and wood energy, and maintaining the area's ecological balance in the face of the worrying advance of the desert. However, these stands are facing increasing pressures that threaten their health and long-term viability. A mixed-methods approach was adopted, combining qualitative and quantitative methods. Field surveys and floristic inventories were carried out to assess the condition of Acacia gum tree stands, with the aim of collecting field data. According to the results on the dynamics of land use change between 2000 and 2023, fields and fallow land have increased by more than 12% of the total surface area, showing that the creation of agricultural plots to meet the needs of local populations has led to the degradation of wooded savannahs and more or less dense galleries. And the spread of bare soil, sandbanks and buildings has led to the degradation of wooded to shrubby savannahs and degraded steppes and shrubby savannahs (a regressive dynamic of 14.64% over 23 years). Secondly, degraded shrub-steppe has fallen from 32.63% in 2000 to 20.69% of the total area in 2023.So, two factors have been at the heart of this mutation: anthropogenic factors (overexploitation of Acacias for firewood, overgrazing, as well as conversion of forest land for agriculture and habitat expansion etc.); natural factors (proliferation of insect pests, rainfall variability, increased drought, land degradation etc.).On the institutional side, institutional inefficiency in charge of the environment. These factors have contributed to the degradation of these natural stands, with detrimental ecological and socio economic effects.