The Dahomey Gap is a biogeographical interruption of the tropical moist forest belt in West Africa, creating a discontinuity between the Upper Guinean forests to the west and the Lower Guinean forests to the east. The gap consists primarily of savanna, dry forest, and agricultural land and extends approximately 400 km along the coastal plain of present‑day Ghana, Togo, Benin, and western Nigeria.
Geography
- Location: Coastal West Africa, roughly between 5° N and 7° N latitude.
- Extent: From the Volta River basin in Ghana eastward through the Ouémé and Niger River basins of Benin into the western part of Nigeria’s Niger Delta.
- Area: Estimates range from 30,000 to 50,000 km², depending on the definition of the forest‑savanna boundary.
Climate
- Rainfall: Mean annual precipitation is 1,200–1,500 mm, lower than the adjacent rainforest zones which receive >2,000 mm.
- Seasonality: A pronounced dry season occurs from November to March, contributing to the dominance of fire‑adapted savanna vegetation.
Ecology
- The gap is dominated by Sudanian–Guinean savanna species such as Panicum grasses, Acacia spp., and fire‑resistant trees like Combretum and Terminalia.
- It acts as a barrier to the dispersal of many obligate forest species, resulting in distinct genetic lineages on either side of the gap (e.g., primates, birds, and certain tree taxa).
- Endemic and near‑endemic species are limited; the region is more notable for its role in shaping distribution patterns rather than for high levels of endemism.
Geology and Soils
- Underlying substrates are largely derived from Precambrian metamorphic and granitic rocks, overlain by lateritic soils that are relatively nutrient‑poor and favor savanna over forest.
Human Influence
- The gap coincides with one of the most densely populated corridors in West Africa. Intensive agriculture (cocoa, palm oil, and tuber cultivation) and urban expansion have further reduced forest cover.
- Historical settlement patterns, including the former Kingdom of Dahomey (now Benin), contributed to the naming of the gap.
Conservation and Research
- Because it separates two major rainforest blocks, the Dahomey Gap is a focal point for studies in biogeography, phylogeography, and climate change impacts on forest fragmentation.
- Conservation efforts are challenged by the high human population density and the prevalence of agriculture, though several protected areas (e.g., W National Park in Benin) lie within or adjacent to the gap.
Etymology
- The name derives from the historic Kingdom of Dahomey, which occupied much of present‑day Benin. The term was first introduced in scientific literature in the mid‑20th century to describe this discontinuity in the West African forest belt.