The Gambia

Major Gambian Land Use Zones

The patterns of land use in The Gambia are related to the different vegetation zones. These again depend heavily on the fluvial influence and soil conditions, as the climatic conditions are relatively homogeneous all over the country. In an overview, it can be stated that the mangroves are fairly untouched by human action and the floodplains are used for irrigated agriculture (e.g. rice) and to some extent for grazing and firewood gathering. The plateau, on the other hand, is subject to rain fed agriculture (mainly food staples and groundnuts) with fallow periods of differing duration, large scale extensive grazing, firewood gathering and different types of human settlement and edification.

Agricultural land: About one third of The Gambian territory is put into active agricultural use, excluding lands lying fallow. Major food crops are early and late millet, rice, maize, sorghum and cassava. Major cash crops are groundnuts, cotton and sesamy. Further, horticulture is widespread. The poorer, but well drained, soils of the plateau are used for all these crops, while the waterlogged lowland soils only are used for the growing of rice. With the exception of irrigated rice fields and domestic gardens, agricultural land use is generally extensive, in the meaning of low/few inputs and low returns. Slash and burn of bush or fallow land and subsistence agriculture is the norm. The current intensively managed area consists of less than 1,200 ha irrigated rice fields and about 800 ha more or less irrigated vegetable and fruit gardens.

The traditional means of keeping soil fertility at satisfactory levels are shifting cultivation and intercropping. Shifting cultivation includes using fallow periods and crop rotation. In The Gambia, traditionally the soil was subject to a fallow period of over twenty years after four years cropping. A typical cycle of crop rotation in The Gambia featured groundnuts in the first year, thereafter late millet, early millet or sorghum and finally groundnuts again. Finally, intercropping is common in The Gambia. Intercropping of different crops, with differing demands of water and nutrients, is an effective way to postpone soil exhaustion. In The Gambia, intercropping of groundnuts with millet and maize, early millet with late millet and maize or sorghum with late millet are somewhat common. Single cropping, with the exception of sorghum, is however getting more and more the norm.

While crop rotation, and to some extent intercropping, still is widely practiced throughout The Gambia, long fallow periods are coming to an end. From a traditionally fallow period of over 20 years, they had dropped to one or two years in 1983, having severe effects on soil fertility. Now, many fields do not experience fallow periods at all. Applying organic fertilizers (manure), has been a traditional means of upgrading soil fertility. Almost 50% of farmers used this method in 1982, but numbers are probably higher today. The use of chemical fertilizers is not widespread in The Gambia.

Bush: Over 60% of The Gambian territory is bush, in the sense of land not in active agricultural use. This includes forests, savannah, fallow lands and mangroves. The bush is, however, in active use as a source of wood and pasture and as a soil restoration of agricultural land. In fact, its use is vital to the rural population, providing key resources. Large cattle herds graze in the plateau bush in the wet season, while the wetlands provide additional fodder resources in the dry season. The dry season represents a bottleneck for animal husbandry, especially because of the low nutritional value of the dried grasses. However, the pasture normally is sufficient for Gambian herds, when there are not bushfires taking a big toll of the pasture locally. Grazing and trampling of the large livestock herds causes substantial stress on the geo-ecological environment. Further, the wood resources of the bush are vital as an energy supply and for construction and fencing. More than 80% of The Gambian national energy consumption was estimated to be firewood in 1995. Wood is generally only collected from dead trees, but the high bushfire frequency due to human activity often causes trees to die. 

Bushfires are in general caused by human activities, and are ignited deliberately or accidentally. Deliberately ignited fires are set to prepare new agricultural land, fertilize agricultural land or to kill or drive away pest animals, such as insects, bush pigs, snakes, parasites, etc. These fires, however, often get out of control and devastate large areas. Most fires, though, are probably ignited accidentally, caused by cigarettes, cooking fires, etc. Bush fires are believed to burn about 80% of the bush annually.

Data: Key data about environmental effects of land use in The Gambia have been produced through satellite images by Deutsche Forstservice GmbH in their "Land Use Inventory for The Gambia" (Ridder; 1991). Combining his results with earlier inventories, Ridder produce a table showing land use and changes in land use in The Gambia (see table 1).

In Ridder’s land use classes, closed forest is defined as forests with a canopy cover exceeding 50% and a tree height of at least 11 m (though not including mangroves), open forests have a crown cover of 10 - 50% and savannah areas have a tree and shrub vegetation of less than 10% crown cover. Cultivated areas are cropland and fields with relatively few or no trees, while the category "other areas" includes mangroves, swamps, water-cover, unvegetated areas and human settlements.

The distribution between closed forest, open forest and savannah does not reflect the natural vegetation zones (although they certainly are influential), but the product of a long history of human land use. The inventory clearly documents trends of deforestation. Areas with dense tree cover tend to get less dense, and the cultivated area is expanding on expense of forests and savannah. Ridder attributes these trends to population growth, causing a bigger demand for firewood, agricultural production and larger livestock herds. Further, bushfires, less precipitation and an ineffective forest administration are to blame.

Another clear trend is the continuous shift from land use classes with high biological productivity to classes with less biological productivity. This is illustrated in table 2, where biological productivity is measured in biomass increment (m³/ha) per year. The exceptions remains the highly productive mangroves, which keep relatively untouched by man. This, due to the regular intrusion of salt sea-water, making them infertile for other than specialized plants.

Consulted Bibliography

Fyhri (1998), The Gambia: The complexity of modernising the agricultural Sector in Africa, thesis in geography, University of Oslo. Available in our library!

Ridder (1991), Land Use Inventory for The Gambia, for Deutsche Forstservice GmbH, München.

Trolldalen (1991), On the Fringe. A systems approach to the evolution of the environment and agricultural production in The Gambia, West Africa 1948-1983, NORAGRIC Occasional Papers Series C, Oslo.

 

© afrol News.    You can contact us at mail@afrol.com