If Lake Malawi didn't exist, the Central Railway wouldn't have to move north, and northern Mozambique, rich in natural harbors, could entirely replace the role of Dar es Salaam City.
Of course, the existence of Lake Malawi has both advantages and disadvantages for East Africa overall; naturally, it's better to have the lake. After all, lakes are precious natural resources, and a giant lake like Lake Malawi is a rare resource for many countries. Moreover, the presence of Lake Malawi doesn't necessarily mean a complete disadvantage in transportation. The Malawi Lake Industrial Zone took shape by relying on the local lake transport industry.
The natural conditions along the Lake Malawi shore are excellent, and it serves as an important transportation link connecting East and Central Africa, allowing for rapid resource circulation within the region.
