South Sudan referendum: 99% vote for independence

The great divide across Sudan is visible even from space, as this Nasa satellite image shows. The northern states are a blanket of desert, broken only by the fertile Nile corridor. Southern Sudan is covered by green swathes of grassland, swamps and tropical forest.

Sudan's arid northern regions are home mainly to Arabic-speaking Muslims. But in Southern Sudan there is no dominant culture. The Dinkas and the Nuers are the largest of more than 200 ethnic groups, each with its own traditional beliefs and languages.

The health inequalities in Sudan are illustrated by infant mortality rates. In Southern Sudan, one in 10 children die before their first birthday. Whereas in the more developed northern states, such as Gezira and White Nile, half of those children would be expected to survive.

The gulf in water resources between north and south is stark. In Khartoum, River Nile, and Gezira states, two-thirds of people have access to piped drinking water and pit latrines. In the south, boreholes and unprotected wells are the main drinking sources. More than 80% of southerners have no toilet facilities whatsoever.

Throughout Sudan, access to primary school education is strongly linked to household earnings. In the poorest parts of the south, less than 1% of children finish primary school. Whereas in the wealthier north, up to 50% of children complete primary level education.

Conflict and poverty are the main causes of food insecurity in Sudan. The residents of war-affected Darfur and Southern Sudan are still greatly dependent on food aid. Far more than in northern states, which tend to be wealthier, more urbanised and less reliant on agriculture.

Sudan exports billions of dollars of oil per year. Southern states produce more than 80% of it, but receive only 50% of the revenue, exacerbating tensions with the north. The oil-rich border region of Abyei is to hold a separate vote on whether to join the north or the south.