Tanzania - a second garden of eden

The Chagga are a mixture of different ethnic groups who settled on Kilimanjaro over the course of time. Even Swahili traders, a coastal people of mixed African and Arabic origin, sometimes decided to settle on the great mountain. All groups brought their specific domestic plants with them. The Swahili played a particularly significant role as importers of maize, cassava, sweet potatoes and other South American plants, to which they had been introduced by contact with the Portuguese as early as the sixteenth century.

This rich mixture of domestic plants eventually inspired a form of land use known as Vihamba, multi-story tree gardens characterized by their great diversity, giving visitors the impression of being in the Garden of Eden. Vihamba originated on patches of forest land where useful species remained standing, while other parts of the natural forest were gradually replaced by cultivated plants from Chagga nurseries.

Irrigation is another special feature of this cultural landscape. Long before the colonial period, the Chagga tapped the water in steep, remote gorges, digging canals and hollowing out tree trunks to conduct it to settlements on mountain ridges. This provided them not only with drinking water, but with water for domestic cattle. Cattle dung in turn, was available and used efficiently to fertilize crops in the tree gardens.

As early as 1885, a packet of coffee seeds from the island of R�union arrived at the mission in Kilema. Within the space of a few years, the Chagga were successfully growing coffee as a cash crop. By 1925 they had integrated well over one million shade tolerant coffee bushes into their Vihambas, and 20 years later the Kilimanjaro Native Co-operative Union had grown to include almost 30,000 members. Many Chagga became involved in trading and transporting their products. Those who were literate soon found jobs in the colonial administration. Even today, many of Tanzania's political and business leaders still from Kilimanjaro.

Between 1940 and 1980 the population grew steadily at around 3 per cent annually, thereby doubling every 20 years. In time, however, the highly innovative Chagga succeeded in striking a balance between population density and land use. Increased productivity in the Vihamba was decisive.

The Chagga have become masters at combining many types of plants which not only require different amounts of light but also have roots of varying depths. For example, yams, a liana with starchy nodules, tolerate the shade of neighbouring trees, and also need the trunks of these trees as climbing supports. Even root nodules growing close to the trunks of trees with deep root systems are able to obtain sufficient nutrients. Today, a Chagga farmer cultivates up to 60 different species of trees - and often many different varieties - on an area the size of a soccer field.

Chagga women and children attend to domestic needs, including production of food, fodder and fuelwood, while the men are concerned with the realms of alcohol and money, or more specifically the production of banana, beer and coffee. Income from coffee is used for school fees and is also invested in homes and farms.

The tree gardens produce considerable yields. In regions inhabited by the Chagga, where the average per capita income is considerably higher than the national average, coffee is the main source of income. In recent years coffee has been Tanzania's most important export.

More difficult to quantify, but certainly of great value, are the many different products grown in the Vihamba for home consumption or for local markets, including fuelwood used for cooking. One hectare is usually sufficient to supply a large family with fuelwood and timber. Women on Kilimanjaro need only a little longer than two hours per week to gather enough fuelwood for their families - much less than in other parts of Tanzania.

One of the most intriguing aspects of tree gardens is the way in which they spread risk by balancing food crops and cash crops. The fluctuating prices of coffee on the world market taught the Chagga at an early stage not to concentrate exclusively on coffee as a source of income. This is why bananas and other products which ensure basic subsistence never disappear from tree gardens even when coffee prices are high, despite the occasional recommendations to the contrary issued by the government-run coffee research station in Lyamangu.

As soon as the price of coffee drops below a certain level, the coffee plants are no longer fertilized, and the rust-fungus which grows on them is no longer treated with expensive fungicides. At this point yams and taro are dug up from "storage". Thus the Chagga system of resource use is not only ecologically but also economically sound.

The Chagga have developed the Vihamba into a complex agroforestry system which is without parallel. Many experts believe the tree gardens could be the starting point for an improved form of land use in tropical ecosystems - for example, in the rain forests of Costa Rica, Indonesia or Brazil.

Christian K�chli is a forest scientist based in Switzerland.

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