Page:Niger Delta Ecosystems- the ERA Handbook, 1998.djvu/42

What is the Environment? 3.4.2 BIOGEOGRAPHICAL REGIONS

These divide the Biosphere into regions of distinct and characteristic combinations of plants and animals across a gradation of climates. They tend to be divided by oceans, deserts and massive mountain ranges. Ecologists differ on the specific definition of the Biogeographical regions but a useful classification defines eight:


 * the Nearctic region - North America;
 * the Neotropical region - South America;
 * the Palearctic region - Eurasia and N. Africa;
 * the Afrotropical region;
 * the Oriental region - India and South East Asia;
 * the Australasian region;
 * the Oceanic region; and
 * the Antarctic.

3.4.3 BIOGEOGRAPHICAL SUB-REGIONS

These define the biogeographical regions in more specific terms and are more closely related to geographic factors such as climate and relative isolation. The Niger Delta is in the West African sub-region, which also includes the Congo river basin and the more humid (southerly) part of the Niger/Benue river basin, as well as all the West African coast the mouth of the Congo.

3.4.4 BIOMES

These are large areas containing characteristic communities of plants and animals. Thus the West African biogeographical sub-region contains both Tropical Rain Forest and savannah biomes.

3.5 ECOSYSTEMS

Ecosystems are what ecologists are really interested in: they describe the mechanics of the landscape.

Technically an Ecosystem is an area within a biome which can be given a physical boundary for convenient ecological study.

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 * as places which can be recognised within their general surroundings, such as the levee forest at Okoroba or a shrine forest at Botam-Tai;
 * as places which are defined by the predominance of one plant species, such as the Rhizophora mangrove forests of Akassa Creek; or
 * as places which are defined by the territory of one animal, such as the Chimpanzees of Okoroba.