Human Ecosystems: Introduction
16.2 THE NATURAL ECOZONES OF THE NIGER DELTA
The Niger Delta is a young, complex and dynamic ecosystem which can be understood in terms of five prime ecozones, unique to it, as described in Chapters 5-9. With the exception of the Estuaries and Offshore-Waters ecozone, the Niger Delta lies within the West African tropical rainforest biome, so that regardless of the human impact, the natural climatic climax vegetation is tropical rainforest. As already explained the prime ecozones group together a variety of subecozones and ecotones by five specific characteristics. Either:
- they have deep soils where drainage is generally not a limiting factor (the Lowland Equatorial Monsoon); or
- they have a fresh-water regime, where, with the exception of levees, excessive soil moisture generally creates reduced soil conditions (the Fresh-Water ecozone); or
- they have a brackish-water regime, where excessive soil moisture creates reduced soil conditions (the Brackish-Water ecozone); or
- they are on a Niger Delta sand barrier island; or
- they are marine (the Estuary and Onshore Waters ecozone).
These definitions help our understanding but the ecozones are no more than convenient boundaries for the description of the Niger Delta ecosystem as a whole. An ecosystem which itself is no more than a convenient boundary for study, and actually an interrelated part of a hierarchy of ecosystems. A hierarchy that may, for example start with the West African biogeographical sub-region and reach down to the estuaries of the Niger Delta and defined species populations that live in them. These ecological interrelationships become more obvious when they are subjected to human influence. For example:
- the man-made Kainji dam, up-stream of the Delta, holds back a substantial amount of the sediment load of the Niger River;
- as a result, the erosion-deposition balance of the Sand Barrier Islands may be tipped in favour of erosion;
- this could reduce the protection that the islands give to the mangrove forests,
- thus reducing the mangroves' vital role in the initiation of the food chain that supports fish production in the offshore waters.
Thus, in the end, the natural ecosystem of the Niger Delta is no more than a conceptual idea to help us understand the human ecosystem that it is today.
16.3 THE HUMAN ECONOMIC IMPACT
An appreciation of history and economic conditions is essential to the understanding of the modern landscape, in addition to an understanding of geography and ecology. To understand the culture of the landscape and how it evolved in relation to the environment, and how, in dynamic relationship, the environment has been shaped by the culture and by outside influences. The country around ancient cities such Benin City or Rome are extraordinary testimonies to the profound influence that a high culture has had on the landscape for hundreds of years.
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