Dry corridor of savanna interrupting the West African rain forest and separating it into two parts known as the western Guinea and Central African Congo zones and reaching the Atlantic coast in Togo and Benin.

Due to the separation, the resident flora and fauna of the Guinea and Congo zones differs to a significant extent.

In terms of climate the gap has been wetter a number of times through history and has existed in its current state for around 4000 years.