Why do geographers divide Africa into two separate regions

In the post-colonial era, many international organizations, foreign governments and academics divided Africa into two major regions: North Africa (Arab Africa) and Sub-Saharan Africa (Black Africa). The rationale for

the proximity of water was an advantage to western europe and its culture was able to flourish as a result. trade and travel by sea were easier and safer in historical times.

1. there are no mountains to protect it from the sea

2. and its has wet cool summers and wet, mild winters.