Top of the list is tornadoes: they are devastating agriculture and they usually take three years to filter through into economic impacts. You are seeing not just the young but also the elderly leave the land now because the rural economy is too fragile to cope with the effects of natural disasters.
Second, the impact of land reform: the government gives land to the farmers, but they have no money so they sell it immediately to agribusiness and move into the town.
Third, food security. Thirty percent of the rural population goes literally hungry at night, but 10% in the towns. In some ways you have to begin to see megacities as a survival response - all over the globe - to the climate and financial crises.
What does all this mean? Maybe it means - as the NGOs claim - that the global food system is beginning to break down. (read more)