What makes Southern Africa a region

One customs area, and one rate of exchange

The Southern African Customs Union rests on an agreement of 1910 between the Union of South Africa and the territories then called Bechuanaland, Basutoland and Swaziland. Independence changed the names on the document rather than the membership: Botswana and Lesotho in 1966, Swaziland in 1968, and a renegotiated agreement signed by the four in 1969. Namibia was administered by South Africa until it took its seat at the United Nations on 23 April 1990, and acceded after that. A further agreement signed in 2002 came into force on 15 July 2004 and gave the union a permanent secretariat, which sits in Windhoek.

Money runs on a separate treaty and a slightly shorter roster. The Common Monetary Area binds South Africa, Lesotho, Namibia and Eswatini under the Multilateral Monetary Agreement of 1992, and the loti, the Namibian dollar and the lilangeni are each exchanged one for one with the rand. Botswana replaced the rand with the pula in 1976 in order to set interest rates of its own, and the difference still shows in the records: Lesotho and Namibia each list two currencies, Botswana one.

Where the edges are argued about

The roster follows the M49 groupings published by the UN Statistics Division, which read Southern Africa narrowly and file Angola under Central Africa and Zambia, Zimbabwe, Malawi and Mozambique under East Africa. The Southern African Development Community reads the region far wider, and its own membership reaches the Democratic Republic of the Congo and Tanzania. Both readings are in ordinary use, and a reader who arrived expecting to find Zimbabwe here has met the wider one. M49 states that its groupings are a statistical convenience implying nothing about political affiliation, and this catalogue takes the same position: the grouping is a way of finding a page, not a claim about who belongs with whom.

What the borders do

South Africa shares a land boundary with every other member, and nothing else in the group touches more than two of its neighbours here. Lesotho has one neighbour in the world and it is South Africa, whose territory surrounds it on all sides. Eswatini has two, South Africa and Mozambique, and only one of those is inside the group. Three members have no coast at all, while South Africa's shoreline runs from the Atlantic round to the Indian Ocean and Namibia's faces the Atlantic alone.

The high ground is held in common as well. Thabana Ntlenyana in Lesotho reaches 3,482 metres and Mafadi in South Africa 3,450 metres, a difference of 32 metres between two summits on the same escarpment. At the other end of the relief, the lowest point recorded for Botswana is the Limpopo at 513 metres, for Lesotho the Orange at 1,400 metres and for Eswatini the Maputo at 21 metres: in each landlocked case a river, and in each case a river that also serves as a border. Standard time across the group is UTC+02:00, and English is an official language in all of them.