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sources of directly consumable goods and as agents for the provision of
indirect products and benefits, has been hailed with conviction and enthusiasm.
However, is this display of confidence with regard to the repeatedly quoted
usefulness matched by evidence in terms of hard facts and quantitative data?
There can be little doubt that basically and in qualitative terms woody
perennials are to be considered useful not only by scientists for academic
purposes but also by farmers and land managers for practical reasons. How
else could the traditional practice of agroforestry with its inclusion of trees
in many places around the world be explained? However, the question must
be asked, 'How useful are they?' If we are to advance to a better understanding
of the complex processes involved in agroforestry systems in order
to assess and evaluate them with the objective of possibly improving the
systems not only ecologically but also economically, the quantification of
products from trees is as important as yield data from crops or livestock.
If agroforestry claims to be superior to other more conventional landuse
systems under certain circumstances, it will have to prove it, and therefore
has to expose itself to a comparison with the latter. This proof, however,
will be conducted by comparative evaluation and by a comparative economic
analysis of systems of different approaches. In such a comparison
agroforestry may stand a chance of emerging as the 'winner' if it is judged
only along environmentally motivated ideological lines, whereby qualifying
and not quantifying its benefits may be considered adequate. But selling
the concept to individual farmers, land owners and land managers, whose
livelihood depends on the economic outcome of the landuse, will require
hard economic facts as the measure by which agroforestry approaches will be
judged. A valid and satisfactory comparative evaluation will depend on a
reasonable level of knowledge of the quantitative productivity of its components,
which often compete for the same piece of land. But even if trees
constitute a desirable supplementary and crop-supporting rather than a
competitive component, as is the case, for example, with Acacia albida
intercropped with millet in some parts of Sahelian Africa, the need remains
to quantify this additional benefit to verify the superiority of such a system.