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Port Harcourt industrial, commercial and administrative purposes, but the majority of the residents live, and much of the commercial and industrial activity takes place in unplanned and unofficial places. Also, growth is rapid and extends into areas that are unsuitable for human habitation. Houses in most areas are overcrowded while basic public services such as treated water, sewage and refuse disposal, and electricity supply are either basic, erratic, or non-existent, in even the most salubrious areas; and pollution levels are high.

The destiny of Port Harcourt is to become the centre of a major conurbation the impetus for growth of which is the oil industry and the continuing rapid regional population growth. Within the next 40 years, trends suggest that the city will become the centre of a conurbation extending North and East in a semi-circle radiating 15-20 kilometres from the State Government Secretariat and extending from the Old Calabar River to the high ground east of the Bonny River. Tentacles will stretch through to Bonny, to Bori, along the main road to Warri, and across the Imo River to Aba. Outlying parts of the conurbation will include Owerri, Aba and Ikot Abasi, giving it a population of between 3 and 5 million people.

21.5 ECOLOGICAL SETTING

Port Harcourt was founded on the very edge of the West African Lowland Equatorial Monsoon ecozone defined as the high ground above the Bonny River, which is the tertiary raised coastal plain of Nigeria. This Port Harcourt ecozone contains as subecozones small areas of West African Fresh-Water Alluvial Monsoon ecosystems, for instance along the Diobu river before it becomes brackish as the Diobu Creek at Amadi Flats. The Lowland Equatorial Monsoon ecozone is the most suitable for urban development within the Niger Delta because the soils are comparatively deep and well drained (which, coupled with high rainfall, is why the natural vegetation climax is a dense tropical rainforest of tall trees). It is in this ecozone that the northward growth of Port Harcourt is occurring.

However, and conversely, the Brackish-water Alluvial Monsoon ecozone upon which the unofficial waterside and official sand-filled development is taking place is not suitable for human settlement having a high brackish water table and being subject to flooding. Naturally the vegetation climax of this ecozone is mangrove forest, although, in the unlikely event of the area being deserted by mankind a post-modern ecological climax would include the Nipa palm, an exotic plant introduced into Nigeria at the beginning of this century.

The waste products of Port Harcourt have a dramatic impact on the Brackish-water ecosystem of the city, especially as the wastes are not easily flushed out of the system into the sea because tides tend to push them back up the Bonny Estuary. Organic products, such as oil, human sewage, and vegetable and animal refuse, may to a certain degree have a positive impact by enriching the nutrient source at the beginning of the food chain. However, if the system is overloaded with such products Biological Oxygen Demand (BOD) by bacteria and other micro-organisms that breakdown the wastes becomes so high that dissolved oxygen in the water is depleted, limiting and even entirely obliterating fish and aquatic plant life. Non-degradable or slowly degradable man-made products, such as plastics, become physically incorporated into the soil structure; but more serious are inorganic compounds, such as heavy metals, which are the by-products of industrial processes, which build up and concentrate down the food chain possibly to toxic levels, and particularly in the filter feeding arthropods and 243