The sparse population in the middle belt of West Africa can be traced to all the following except

Analyze the question: This is an "except" question. Three options are real causes of sparse population in the Middle Belt of West Africa, and one is not. We need to find the one that is NOT a cause.

Concept: The Middle Belt (the Guinea savanna zone between the forest in the south and the Sudan savanna in the north) is known for low population density. The main historical and environmental reasons include:

• Tsetse fly infestation: The fly spreads sleeping sickness in humans and nagana in cattle. This discouraged settlement and livestock keeping.
• Inter-ethnic wars and slave raiding: Conflicts in the 18th-19th centuries (for example, the Fulani jihads and Yoruba wars) depopulated or displaced people from the area.
• Slave trade: Raids, including those linked to the trans-Saharan (Arab) trade, drew captives from the Middle Belt and left it depopulated.
• Poor soils and unreliable water supply in some parts.

Step by step:

1. A. Concentration of industries: Industries attract people and create dense populations (e.g., Lagos, Kano, Ibadan). The Middle Belt is not heavily industrialised, and industry would increase population, not reduce it. So this is not a cause of sparse population.
2. B. Inter-ethnic war: This is a cause, as it forced people to flee or killed many.
3. C. Tsetse fly infestation: This is a cause, as it made the area unhealthy for people and livestock.
4. D. Arab slave trade in the north: This is a cause, as raids took away much of the able-bodied population.

Tip: In "all of the following except" questions, find the option that works in the opposite direction. Here, industries attract people, while war, disease and slave raiding drive them away. Industry is the odd one out.