All Western cities face significant challenges on social integration. Our populations are booming, but social integration is not keeping pace. Rapid growth is a sign of our success, but it also puts stress on housing, infrastructure - and on communities.
The factors that have been holding farmers back are similar to those that threaten other types of growth in Africa. Infrastructure and transport are in many cases quite poor, resulting in the losses of huge amounts of produce.
The bigger the city is, the less infrastructure you need per capita.