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Environment and health
Desertification is by far the most pressing environmental problem in the northern states along the border with Niger. Nigeria is presently losing about 351 000 km² of its land mass to the desert which is advancing southward at the rate of 0.6 km/year.
Soil degradation is induced by human activities, such as:
- Urban encroachment due to overpopulation, where some farmlands have been converted into urban areas; concentration of intensive agriculture around urban centres exacerbates degradation of land and water resources.
- Deforestation due to uncontrolled land clearings for construction or agriculture purposes.
- Inappropriate use of agro-chemicals and the concomitant problems of chemical persistence in the soil in humid areas and soil-crust formation in arid climates, which have contributed to salinization and destruction of vast agricultural lands. The coastal areas of Nigeria are heavily affected by salinization.
Loss of water bodies and lowlands
Hydrology downstream from dams and major diversions and pumping stations has been modified, especially in the north. Extensive areas of fadama, fisheries and wildlife habitats were wiped out.
The Hadejia Nguru Wetlands in the northeast of the country receive their water from the Hadejia and Jama’are rivers, which meet to form the Komadougou Yobe river, flowing northeast into Lake Chad. So far, more than half of the wetlands have been lost due to drought and upstream dams. New development could divert still more water from the wetlands for irrigated agriculture in upstream areas, affecting both the ecology and the irrigated agricultural production in the floodplain using water from the shallow groundwater aquifer, as recharging would decrease further.
Inappropriate agricultural practices, such as lack of crop rotation, adoption of maximum tillage, inadequate or total lack of fallowing, inadequate fertilization, overgrazing, absence of mulching, and the opening up of riverbanks have led to silting of riverbeds and loss of watercourses.
Groundwater overexploitation and quality
Expansion of irrigated crop production in the fadama lands has led to a lowering of the water table in some areas. Overexploitation of groundwater starts to be felt in some areas also for industrial and municipal use due to the non-enforcement of controlled drilling. In the northern areas, it could build-up salinity and in the southern parts, salt-water intrusions are threatening due to the lowering of the groundwater table, as it is already the case in metropolitan areas such as Lagos and Port Harcourt, located in the coastal plains.
The quality of the groundwater is generally good. The occurrence of iron rich water in the Niger Delta can sometimes constitute a major problem in some isolated localities in the dry deltaic plains (AfDB, 2013).
Surface water quality
Wastewater treatment is almost inexistent, so most of the wastewater reaches water bodies without any treatment. The water quality of rivers is strongly influenced by human activities especially when passing through urban, industrial and agricultural areas. Generally, the water quality of rivers is good in the southern areas, but in the northern areas water quality decreases in the dry season with low flows.
In the Niger Delta, water resources are being polluted from oil exploration activities such as oil drilling and pipe leakages and vast farmlands have been destructed.