The Chad government has become increasingly aware that there is a localised problem in the conservation and management of woodland in the region around its capital city, NDjamena. This situation has arisen for two main reasons:
(ii) NDjamena is located in the fragile Sahelian zone.
I.S. Ltd, together with the Department of Geography at the University of Leicester was awarded a contract to
(i) carry out a fuelwood inventory of a region within 125 km of NDjamena;
(ii) look at the change in woodland over the previous 10 year period;
(iii) provide a starting point upon which a woodland management plan could be devised.
Satellite data from SPOT provided information on the status of the fuelwood supply in 1994/5 (7 scenes), and Landsat Thematic Mapper data provided information on the woodland status in 1986 (2 scenes). These data, together with field measurements collected over a two week period in November 1995, have enabled I.S. Ltd to produce a fuelwood resources inventory.
Estimates of woody biomass from field measurements varied widely; from a minimum of 0.03dt/ha in the most severely degraded site to 0.52dt/ha in a site which was seasonally inundated. A large proportion of the sites had low levels of biomass (57% less than 5dt/ha, and 84% less than 15dt/ha). From these measurements three broad classes of woodland were derived: Semi-desert wooded grassland; Moist Acacia-Commiphora Bushland (Acacia Bushland); and Dry Sudanian woodland.
The satellite images were geometrically corrected, mosaiced, and classified using a maximum likelihood classifier. All processing was carried out using PCIs EASI/PACE image processing system. From the classification results the total proportion of woodland was calculated to be 30%. Half of this total is accounted for by Acacia Bushland. From these area measurements, the productivity was calculated by combining the yield (which was assumed to be 10% of the dry woody biomass measurements) with the area for each woodland type. The maximum estimated productivity of the region was calculated to be 580592 tonnes of fuelwood (1995).
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The World Bank has found that in other parts of the Sahel, the most efficient form of management has been to implement local, village-based structures rather than impose centralised control.
The initial task involved the identification of villages from the SPOT satellite imagery (881 in total), and the application of buffer zones around each village. [Note that the best current mapping for the area was 1:200000 scale maps produced by the Institut Geographique National in 1958 / 1959.] Each buffer zone was 10 km, the estimate of the woodland catchment for each village. The zonation involved three categories: red - non-commercial protected areas; yellow - non-managed resources away from population centres; and green -managed resources, where the management will be carried out by each village.
The woodland classification derived from the SPOT satellite imagery was superimposed upon this zonation in order to assist in the development of management practises. Research undertaken elsewhere in sub-Saharan Africa suggests that the development of village-based management systems should be based on the existing, indigenous woody biomass management systems in the region. The basic principle behind the management of wood resources in the green zones' should be sustainability. This will involve setting targets for fuelwood offtakes (as well as other offtakes) based on wood productivity that enable both the ecosystem and the village economy to continue at current or enhanced levels of production.
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It can be concluded that whilst the maximum estimated productivity of the region is sufficient to meet current demands for fuelwood, it would not meet the demand if urban households switched en masse to charcoal. The fuelwood supply / demand situation in the N'Djamena region of Chad is therefore finely balanced.
There is a need to implement a woodland management strategy to preserve woodland stocks, and through the use of supply enhancement techniques such as enrichment planting to increase stocks. In addition alternative fuels such as butane gas may need to be sought, together with the introduction of improved stoves. The butane gas solution is particularly attractive in the light of the development of oil fields in Chad. It is to be hoped that the oil resource is used wisely.
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