Juliet Prior is at the Department of Pure and Applied Biology, Imperial College of Science and Technology, Prince Consort Road, London SW7 2BB, England. She emphasises the need for closer liaison between project planners and research workers.

A wealth of evidence concerning Man's past choice of fuelwood exists in archaeological sites throughout Africa, yet this information has been largely ignored. Trees have long been vital throughout the rural drylands of Africa, where up to 90% of the local population still depend upon fuelwood supplies for cooking and heating. Deforestation is resulting in many households being close to the minimum energy requirement for basic needs; an increasing number are falling below this level.

Few rural Africans have funds for the purchase of alternative energy sources and populations are currently increasing at an annual rate estimated to be approximately 2.6%. Since none of the principal food crops the tropics and sub-tropics is palatable when uncooked, it follows that a lack of fuel is becoming as much a cause of malnutrition as crop shortages.

Recent reports by multi-lateral agencies such as the Food and Agriculture Organisation of the United Nations, stress the severity of the present fuelwood crisis and recommended a five-fold increase in the annual rate of tree planting by the end of the century.

Of recent years, forestry schemes in operation in the arid and semi-arid tropics have concentrated upon the use of fast growing exotics, particularly those originating in Australia and Central and South America. Many of the species concerned are of commercial importance, so stocks are readily available and the silvicultural techniques needed to introduce wood of the desired quality are well established.

Yet a recent report from Botswana states that the production of Eucalyptus trees is no solution to the fuelwood problem and an evaluation of results obtained in the Northern Sudan and Sahel regions has led to the conclusion that exotics are often unsatisfactory in such harsh environments.

Increased attention is now being focused upon the use of multi- purpose, indigenous trees in future agroforestry schemes. These trees were not previously considered on account of their slow growth rate, yet the wood ultimately produced is dense, slow burning and of high calorific value. Further, the multi-stemmed growth habit of many species is ideal for coppicing, a technique which ensures a continuous supply of small pieces of wood, suitable for domestic fires.

No nursery stocks of seed from such trees exist and many of the trees concerned, such as Acacia species, are thought to be cross pollinating. Whilst cross pollination leads to genetic variation which is of considerable survival value to the species as a whole, it does not necessarily ensure maximum survival of a species in the more extreme parts of its range.

In environmentally hostile, drought stricken areas it is vegetatively produced seedlings, possessing the combination of characters known to be most suitable for survival in a particular area, which will have the best chance of success. Vegetative propagation of suitable seedlings cannot therefore take place without a full understanding of the structure and functional characteristics which impart drought tolerance. Little information of this type is currently available.

Archaeological Evidence

What kind of archaeological evidence is being largely ignored? Charcoal fragments excavated from a rock shelter in Swaziland, Southern Africa, represent the remains of trees and shrubs selected as fuelwood by successive populations over a period of at least 10,000 years. The changing spectrum of woods used reflects minor climatic fluctuations. The charcoals have been identified at Imperial College, London, using scanning electron microscopy and charred, modern comparative material. Certain aspects of the results are of particular significance today. Past fuelwoods chosen, even in moister periods when trees and shrubs were particularly abundant, belonged almost exclusively to two families, the Combretaceae (leadwoods) and the Leguminosae (acacias and sickle bush). Recent village energy surveys in southern Africa have shown that it is members of these families which are still preferred today.

Field studies, using modern plants belonging to these same species, show that in drought stricken areas, survival is dependent not only upon gelatinous fibre formation but upon complementary physiological mechanisms which minimise water loss and enable vital processes to be maintained in areas of particularly low nutrient availability. Further research is urgently required, so that the mechanisms imparting drought tolerance can be fully understood before suitable stocks are produced.
Last edited by Miriam Hansen .
Page last modified on Thursday October 7, 2010 09:19:11 GMT.
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