Page:Niger Delta Ecosystems- the ERA Handbook, 1998.djvu/50

What is the Niger Delta? 4 WHAT IS THE NIGER DELTA?


 * A Unique Ecosystem
 * Relief
 * Local Climate
 * Hydrology
 * Soils
 * Natural Vegetation
 * Natural Animal Communities
 * The Natural Ecosystem

4.1 A UNIQUE ECOSYSTEM

The Niger Delta is unique by virtue of its size (nearly 26,000 km2 – see 11.2), its location and its origins.

Although it is situated in one of the wettest places on earth, it is fed by a river that passes largely through Sahel and dry savannah landscapes - geologically, some of the oldest on earth.

Considering the other continents, there are also few comparisons lying within the tropics. The Ganges Delta is only just within the tropics, but the Ganges Plain itself, to the North, is largely fed by the young Himalayan mountains. The large South American rivers reach the sea through flooded valleys rather than deltas; the Orinoco has a delta at latitude 10 degrees north, but its catchment is very different, lying within the Andes mountains and then a humid plain. Similar ecosystems to the Niger Delta might be expected in some of the Southeast Asian deltas such as the Mekong or the Fly (in New Guinea). However these river systems are shorter than the Niger/Benue and again run through humid plains rather than dry Savannah.

Some of the smaller deltas along the West African coast are similar, but they largely drain humid biomes. The Volta is an exception; Map 3 shows its large catchment area in the dry Savannah hinterland. However it discharges in the Dahomey Gap, an area of low rainfall, and could never have been a similar ecozone to the Niger Delta. (Human activity has also markedly changed the Volta delta, now being rapidly lost to coastal erosion as the Volta Dam traps most of the river's sediment load.)

Map 1 shows the Niger Delta in relation to the rest of Africa. It is a huge fan of land, fed by deposition from the Niger-Benue river system as it spreads out to reach the Atlantic Ocean on the coast of Nigeria. The Niger Delta lies just North of the equator, facing the Southeast trade winds in one of the areas of highest rainfall.

Map 1 also shows the West African biomes and how the forest biome relates to rainfall. The Dahomey Gap, an area of savannah country on the Ghana coast, separates the two distinct areas or sub-regions of high rainfall forest biomes.

In biogeographical terms, the Delta lies in the West African sub-region of the Afrotropical region. The following sections describe the principal parameters of the Delta in its physical geography and as an ecosystem. 48