There are those who blame poor husbandry in the interior. They say indiscriminate development and bad farming practice on the central uplands of southern Africa have destroyed the indigenous capacity of the region's grasslands and wetlands to absorb the naturally recurring periods of heavy rainfall.
They liken the central plateau, which runs northwards from the Cape, to a roof on which the downward folds of the escarpment act as gutters to channel the rain through the river systems to the ocean. The grasslands and wetlands, acting like sponges, so they say, were able to control this system; but with their capability in this respect diminished, the untrammelled waters rush headlong to the sea, overflowing their banks and resulting in the misery that is Mozambique today.
They may be right. On the other hand, there is no doubt that the recent rainfall in the region has been exceptional. And to understand the reasons why, we have to recall a phenomenon that became a household word three years ago: El Nino.
El Nino, literally "the boy child", is the name given to a periodic warming of the surface waters of the eastern tropical Pacific Ocean, which occurs every three to seven years. This warming adds extra energy to the atmosphere, and the climatic effects reverberate around the world.
During an El Nino episode, the normally arid western coasts of South America are drenched with rain, the Indian monsoon may falter, and Indonesia and parts of Australia suffer serious drought. A particularly strong El Nino occurred in 1997/98.
Less well known, however, is El Nino's alter ego, , called La Nina, or "the girl child". The La Nina phenomenon sometimes happens in the gaps between El Ninos, and is a spell when the surface waters of the tropical Pacific are anomalously cold. . The present La Nina is in its second year and it, too, has a pervasive effect upon the global climate, notably on the Intertropical Convergence Zone in Africa.
The ITZ is the region in the vicinity of the equator where the south-east trade winds of the southern hemisphere meet their northern counterparts, the north-east trades; it is a narrow zone of high rainfall that moves north and south with the seasons. From December to March it lies close to Zimbabwe, Zambia and Mozambique, providing these countries with their normal rainy season.
During a La Nina episode, however, rainfall productivity in the ITZ is often significantly enhanced; add in a tropical cyclone or two - also more frequent in the Indian Ocean with La Nina - and the present miseries of Mozambique are understandable.