Final answer:
The Sahel region has transitioned from a once prosperous civilization with ample biodiversity to a barren desert due to climate change and overgrazing, indicative of desertification. Historical evidence shows that the Sahara enjoyed tropical conditions in the post-Ice Age period, but saw desert zones expand dramatically from around 6000 to 2500 BCE.
Step-by-step explanation:
The region that was once a prosperous civilization but has become a barren desert due to deforestation is the Sahel. The Sahel is a transition zone in Africa between the Sahara Desert to the north and the savannas to the south. It has been affected heavily by desertification due to factors such as climate change and overgrazing by livestock. Historically, the Sahel and the larger Sahara region enjoyed more fertile conditions with ample biodiversity. The Sahara, which is the largest desert in the world, is expanding southwards and bringing about significant ecological and economic changes. In the post-Ice Age period, much of the Sahara experienced tropical conditions with monsoon-like climate, supporting pastoralists and their herds. However, a great drying occurred between 6000 and 2500 BCE, leading to the expansion of desert zones and significant challenges for the inhabitants, whose traditional ways of life became unsustainable in the new, harsher environment.