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What is the Environment? However, the activities of mankind can have a profound influence on the hydrology of an area. For instance a natural forest ecosystem tends to act as a sponge, soaking up water in wet weather and releasing it slowly in dry thus moderating the water supply to a river systems. Where natural forest is removed or substantially transformed this sponge function of the forest—effectively a natural reservoir—is lost so that flooding becomes more frequent in wet weather and river failure in dry. The same process may apply to lakes and to ground water systems.

3.2.4 SOILS

Soil forming processes are a function of geology, topography, climate and hydrology and it is important to stress that soils are the unique expression of these predetermining factors.

Thus, for instance, a soil formed on the tropical coast, on alluvial deposits, will have quite different characteristics from a soil formed on the same latitude, with the same rainfall patterns, on a hillside at an altitude of 500m. Moreover, it will have different characteristics from a coastal soil formed on alluvial deposits in the temperate zone.

A soil map of the Niger Delta would show a complex series of soils, the common feature being that they are all the result of a tropical rainy climate. This ensures that they tend to be either highly leached and eroded (where there is free drainage), or arising from rapid rates of deposition and subject to water-logging (for instance the peat swamp soils and the mangrove soils). Moreover in certain conditions—river terraces for instance—soil formation is subject to a dynamic combination of both these activities.

Within this general climatic condition soils are differentiated both regionally and locally by geology and by topographical features.

It is important to remember that soils are alive so that their characteristic are as dependent on microbiotic life forms, such as fungi and bacteria, as they are upon water, mineral particles and humus.

3.2.5 VEGETATION

Natural vegetation climaxes are determined by soil conditions.

If the soil conditions are themselves understood in terms of their relationship to geology, topography, climate and hydrology, then there is no need to go beyond soil conditions in order to understand vegetation climaxes. This must be stressed, because too often vegetation is described purely in terms of "Latitude, Altitude and Climate." This is not sufficient for ecological purposes: the soil must be understood first.

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In terms of plant diversity, the general rule is that the warmer and wetter the climate, the greater the diversity. It is not surprising, therefore, that the Niger Delta has international significance in terms of its importance to the maintenance of global biodiversity.

3.2.6 ANIMAL COMMUNITIES AND HABITATS

Within a given climate, vegetation and hydrology/water quality define animal habitats which in turn determine animal communities. Thus a consideration of animal communities involves an understanding of their habitats, both aquatic and terrestrial (and many animals, it must be remembered, inhabit both). 37