Factors Affecting the Climate of Africa Latitude: Latitude refers to the location of a place on the earth’s surface in relation to the equator. Tropical latitudes where the sun’s altitude is always high have hotter temperature than lower latitudes where the sun’s altitude is generally low. These differences in temperature in relation to different latitudes affect climate. Altitude: Altitude refers to the height of a place above the sea-level. As one moves higher into the atmosphere, the temperature decreases by 6.5˚C for every 1000m of ascent. This is called the normal lapse rate. High altitudes like high mountains contain less dust and water vapour and so allow heat to escape easily and remain cold. Continentality or distance from the sea: Land surface heats up and cools more quickly than sea surfaces. As a result of this, the sea warms coastal regions in winter but cools them in summer. The warming and cooling effects of the sea are felt in areas closer to the coast than the hinterlands. Similarly, rain bearing winds drop more water in the coastal areas and less water as the wind moves into the hinterland. Ocean currents: Ocean currents affect temperature. Warm ocean currents keep the surrounding lowlands warm. They lower summer temperature especially when carrying onshore winds. They force rain bearing wind to drop most water into the sea thereby, making the coastal land dry. Planetary winds and pressure belts: Onshore winds tend to lower summer temperature and raise winter temperature in temperate latitudes. In tropical climates, winds have a cooling effect on day temperatures and a warming effect on night temperatures. Pressure belts also have direct effect on winds in the sense that wind blows from the area of high pressure to area of low pressure. Slope and aspect: Steep slope experiences more rapid change in temperature than a gentle slope. Cloud cover: Cloud reduces the amount of solar radiation reaching the earth’s surface and the amount of solar radiation escaping from the earth surface into space. Day temperature in the equatorial region is always high because of the heavy cloud cover. Natural vegetation and soil: The thick foliage (leaves) of heavy forest cut off much of the incoming sunlight energy (insolation). As a result, the forest temperature is cooler and lower than that of the open ground (soil). Light soils reflect more heat than darker soils which are better absorbers of heat. Types of Climate in Africa The climatic types of Africa include: The Equatorial Hot Climate: This is found in the Zaire Basin of Central Africa and in the Coast of West Africa (Except that of Ghana). Characteristics of the Climate It has constant high temperature with daily temperature of 26˚C with no winter. It has high annual rainfall of over 200cm and rainfall is throughout the year. It has small annual temperature range of 2˚C – 3˚C. It has high humidity all year round with double maxima of rainfall. It has convectional rainfall accompanied by lightning and thunder. The Tropical Continental (Sudan) Climate: This is found in West Africa, and then curves southwards in East Africa and Southern Africa. Characteristics of the Climate The climate is characterized by hot, rainy and cool dry seasons. Extremes of temperature which varies from 21˚C – 32˚C. The annual temperature range is about 11˚C. High monthly temperature of about 27˚C. Annual rainfall is about 600 – 1500mm. Rainfall is seasonal mainly in summer. Rainfall is mainly convectional with single maximum. The Mediterranean Climate: This is found in the horns or tips of Africa. In other words, it is found in south western part of South Africa (Cape Town) and the North West of Africa (Morocco, Algeria and Tunisia). Characteristics of the Climate A dry warm summer of between 21˚C – 27˚C. Abundance of rainfall in winter with mean annual rainfall of 600-800m. Bright, sunny weather with hot, dry summer and wet mild winter. Prominence of local winds around the Mediterranean Sea such as Sirocco and Mistral. The Hot Desert Climate: This climate is found in Sahara desert. It is caused by cold Canary current in North-West Africa and the Kalahari and Namib deserts caused by cold Benguella current in southern Africa. Characteristics of the Climate High temperatures between 30˚C to 60˚C. Aridity or rainlessness is a common feature. Annual range of temperature varies from 9˚C to 20˚C. Annual rainfall is about 250mm. High rate of evaporation. Deserts are associated with cold currents. The relative humidity is very low. The Warm Temperate Eastern Margin: This is only found in southern-eastern margin of Southern Africa (in Natal province). Characteristics of the Climate It has a warm wet summer and a cool dry winter. Mean monthly temperature is between 4˚C and 26˚C. Annual temperature range is 25˚C. Annual rainfall is between 600 – 1500mm. The Temperate Continental (Steppe): This is the temperate grasslands. Example is found in the veld of South Africa. Characteristics of the Climate The vegetation is associated with the temperate continental climate, also called the steppe. Hot summer with temperature of over 20˚C. Cold winter with temperature below 0˚C. Average rainfall is about 508mm. Rainfall is convectional and light. Characteristics of the Vegetation The dominant vegetation cover is savanna. The grasses have different names in different areas where they are found. These are: The Steppe of Central Europe and Russia, The Prairies of North America, The Pampas of Argentina, The Veld of South Africa, The Downs of Australia. Economic Importance Mechanized agriculture is practiced where crops are grown with the aid of irrigation. Pastoral farming is also practiced due to abundance of grasses. The grassland is used as tourist centres. Nomadic herding is also carried out by the local people. The savanna is also used for game reserves for wildlife for (wild animals).
Factors Affecting Vegetation The factors affecting the vegetation of Africa include: Climatic factors. Geomorphic factors. Edaphic factors. Biotic factors. Climatic Factors High temperature with low rainfall leads to sparse vegetation. The higher the rainfall, the denser the vegetation. High temperature and high rainfall lead to luxuriant vegetation. Where temperature is low, no plant grows. Sunshine provides energy for photosynthesis needed for luxuriant growth. Geomorphic or Topographic Factors The steeper the slope, the lesser the vegetation. Rainfall on steep slopes leads to run-off, leading to low vegetation. Eroded top soil in sloppy area does not support vegetation growth. Given the same climate and soil, flat lands have denser vegetation. In higher latitudes, aspect plays an important role on available energy and vegetation distribution. Edaphic or Soil Factors The type of soil in an area affects the rate of percolation of water. Sandy soils are loose and porous, leading to sparse vegetation. Clayey soils do not allow percolation but support little vegetation more than sandy soil. Loamy soil supports luxuriant vegetative growth. The type of soil determines what plant would grow there. Biotic or Human Factors The activities of man either support or reduce vegetation. Bush burning reduces vegetation. Cultivation and animal grazing reduce vegetation. Deforestation also reduces vegetation. Excavation and mining reduce vegetation. Afforestation and irrigation support vegetation. Types of Vegetation in Africa The vegetation types in Africa include: Tropical Rainforest: This is found in Zaire Basin of central Africa and the coasts of West Africa. It is associated with equatorial climate. Climatic Conditions Affecting the Vegetation Favourable temperature of 26˚C with an annual range of 2˚C – 3˚C. Rainfall throughout the year with two peaks (double maxima). Annual rainfall of over 2000mm. Abundant sunshine and fertile soils. Vegetation Characteristics Forest is evergreen with broad leaves. There are various layers of trees – lower, middle and upper storeys or canopies. Trees are of great varieties i.e. trees are heterogeneous. Trees are not in pure stand i.e. they are scattered. Presence of abundant hardwoods. Presence of creepers, climbers, epiphytes and parasitic plants. The forest has little undergrowth. Plant communities The rainforest provides tropical hardwood which includes Iroko, Obeche, Mahogany, Ebony, African Walnut, Opepe, Limba, etc. These woods provide timber for building and other constructions. Economic Importance Provision of hardwood which is the source of timber used for buildings, furniture and other constructions. Lumbering is one of the major occupations of the people due to the presence of numerous timbers. Cultivation of food and cash crops like yam, cassava, cocoa, oil palm, rubber, etc. Hunting of wild animals. Rainforests are also tourist centres. Provision of foreign exchange through the export of timber and other products. Tropical Savanna (grassland): This is found in West Africa, East Africa and southern Africa. It is associated with the tropical continental (Sudan) type of climate. Climatic Factors Affecting Distribution Vegetation Characteristics The dominant vegetation cover is grass; hence, the name given to the grassland is Savanna or Parkland. Presence of tall grasses that is fibrous when old. The trees are deciduous i.e. they shed their leaves during the dry season to reduce transpiration. Plant Communities The major plants are grasses called savanna (in Africa and Australia), campos (in Brazil) and lanos (in Orinoco in South America). Popular trees include acacia, baobab and shea-butter. Economic Importance Livestock farming due to presence of abundant grasses and low Tsetse fly infestation. Arable crop production like rice, maize, millet, sorghum, etc. People are involved in hunting for wild animals. Savanna is a centre of tourism. Nomadic herding is also carried out by the local people. The savanna is also used for game reserves or wild life. The Mediterranean Vegetation: This is found in the North West of Africa (Algeria, Morocco, and Tunisia) and in South Africa (Cape Town). Vegetation Characteristics The trees are evergreen. Plants are adapted to long period of drought prevalent in the region: Tough, small, leathery, hairy leaves to guard against excessive transpiration. Some plants like Oak have tough, thick bark which helps to reduce the rate of transpiration. Some have long roots for drawing moisture from deep down the soil. The trees have slow growth throughout the year but quicker growth during the winter rains. Plant Communities The dominant plant species are the evergreen wood plants such as oak, wild olive, cypress and redwood. Presence of evergreen coniferous tree (soft wood) such as pines, firs and cedars. Presence of Mediterranean bushes and shrubs such as acacia, laurel, rosemary and marquis. Economic Importance Orchard farming where wide varieties of citrus fruits like grape, lemon, orange, etc. are grown. These are used in wine making. Viticulture, which is the cultivation of grape fruits, is common. Production of oak cork used in corking bottled wine. Trees also provide wood for construction purposes. Desert Vegetation: This is found in the Sahara, Namib and Kalahari deserts. Climatic Characteristics High temperature between 30˚C and 60˚C. Aridity or rainlessness is common. Annual range of temperature varies from 9˚C to 20˚C. Annual rainfall is about 250mm. High rate of evaporation. Deserts are associated with cold currents. The relative humidity is very low. Vegetation Characteristics Vegetation in deserts is sparse or scanty. Common vegetation includes grass, shrub and herbs. Most plants are xerophytes (drought resistant plants) like thorny bushes, the bulbous cacti, wiring grasses, date palm and acacia. Some plants are halophytes (salt tolerant plants). Adaptations of Plants to Desert Climate Possession of long roots to search for water in the soil. Presence of few and wiring leaves or no leaves at all to prevent transpiration. Presence of wax on leaves to prevent transpiration. Some possess thick succulent stems e.g. cacti, to store excess water. Some shed their leaves during drought. Human Activities Food gathering e.g. fruits. Nomadic hunting for wild animals. Nomadic pastoral farming e.g. rearing of cattle. Crop production like cotton, rice, sugar cane, millet, etc. with the aid of irrigation. Temperate Grassland (High Veld): This is found in South Africa. Vegetation Characteristics The dominant vegetation cover is grass; hence, the name given to grass land is Savanna or Parkland. Presence of tall grasses that becomes fibrous when old. Presence of short scattered trees. The trees are deciduous i.e. they shed their leaves during the dry season to reduce transpiration. Plant Communities The major plants are grasses called savanna (in Africa and Australia), campos (in Brazil) and lanos (in Orinoco in South America). Popular trees include acacia, baobab and shea-butter. Economic Importance Livestock farming due to presence of abundant grasses and low Tsetse fly infestation. Arable crop production in rice, maize, millet, sorghum, etc. People are involved in hunting f wild animals. Savanna is a centre of tourism. Nomadic herding is also carried out by the local people. The savanna is also used for game reserves or wildlife. Montane Vegetation: This is found in Ethiopia, Mts. of East Africa and Mount Cameroun. Thick forest is found on the windward and light vegetation on the leeward side of the highland.
Drainage refers to water bodies like rivers and lakes. Drainage of Nigeria is discussed in two parts – rivers and lakes. RIVERS IN NIGERIA: Nigeria is drained by two main rivers – Rivers Niger and Benue. River Niger, the largest river in Nigeria has its source from Guinea highlands in Guinea. It passes through Mali and Niger Republic to Nigeria. River Benue has its source from eastern highlands and joins the Niger at Lokoja. Because of this, Lokoja is known as a confluence town. Other rivers in Nigeria take their sources from highlands in Nigeria known as Hydrological centres. These are: Western Highlands: They have rivers such as Ogun, Osun and Osse which flow directly into the Atlantic Ocean. North-Central Highlands: They have such rivers as Kaduna, Hadeija, Zamfara, Yobe, Gana, Gongola and Rima. Eastern Highlands: They have rivers like Donga and Kastina-Ala. Eastern Scarplands: They have rivers like Anambra and Cross River. Characteristics of Nigeria Rivers The volume of water increases during the rainy season and decreases during the dry season. Most rivers have rapids and cataracts which impede or disturb inland navigation. Most Nigerian rivers do have lots of debris like dead leaves, mud, wood, etc. when they flow through forest. Most rivers are usually very short and flow rapidly or swiftly e.g. Rivers Ogun, Osun and Cross River. Rivers in the south flow in the north-south direction into the sea while rivers in the north flow in a radial pattern to different directions. Most rivers are very shallow and full of silt associated with high evaporation and seepage of water into the soil. The rivers have muddy and dirty colour during rainy season but remain clear and clean during dry season. Most rivers flow during rainy season but stop or reduce flowing during the dry season. Importance of Nigerian Rivers Rivers, especially the large ones serves as medium of transportation from one place to another. Many rivers are dammed in areas of water fall and rapids for the purpose of generating electricity. Water from rivers is used for irrigation purposes (i.e. irrigation agriculture) especially in areas of low rainfall to aid crop cultivation. Water from rivers is used for various domestic purposes such as cooking, washing, bathing and drinking. Water from rivers is also required by many industries such as textile, brewery and chemical industries. Rivers do provide employment to many people e.g. fishermen, canoe and ship builders. Rivers are known to provide food for man in form of fish, prawns, crayfish, crab, etc. Some rivers are centers of tourist attraction and may generate foreign exchange for a nation. Some rivers are good sites for the construction of seaports and river ports. Formation of flood plains by rivers also provides fertile soil for agricultural activities. Problems Encountered in the utilization of Nigeria Rivers Seasonal fluctuation of the water volume. Rapids and falls on the rivers. Growth of water weeds. Narrow channels. River pollution. Inland drainage into lakes. Silting at river mouths. Shallow channels. Shortness of rivers. RIVER BASIN River basin refers to the area generally drained by a river and its tributaries. In other words, river basins are naturally depressed lowland areas. River basin is also called catchment area. In Nigeria, there are five major river basins. These are: The Niger Basin. The Benue Basin. The Chad Basin. The Cross River Basin. The South Atlantic Basin. The rivers in these basins are grouped into three classes of: Long rivers with large basin: These Rivers flow to the sea across long distances through the land e.g. Rivers Niger and Benue. Short rivers with small basin: These Rivers also flow to the sea but are very short e.g. Rivers Osun, Ogun, Cross river, etc. Rivers in basins of inland drainage: These Rivers do not reach the sea but rather they flow into Lake Chad e.g. Rivers Yobe, Hadeija and Yedseram and Gana. Importance of River Basins As a result of the fact that river basins are depressed lowlands, it enables people to settle and build houses. Some river basins with alluvial plains are fertile lands for agricultural purposes. The presence of rivers enables people to transport themselves and their goods from one place to another. Depressed or lowland areas do serve as deposits for minerals e.g. petroleum. Water from rivers in the basins may be used for domestic and industrial purposes. Rivers in the basins do provide or act as fishing ground for fishermen. LAKES IN NIGERIA: A lake is a body of water surrounded by land. The lakes in Nigeria are grouped into two major types. Man-made or artificial lakes: These lakes are constructed by man. Examples of such lakes are Lake Kainji on River Niger and Shiroro Lake on River Kaduna. Natural lakes: These are lakes which exist naturally. The only popular example is Lake Chad. Lake Chad is also described as an inland drainage because it receives water from many rivers such as Hadeija, Gana, Yobe, Yedseram. In spite of the fact that Lake Chad receives water from many rivers. It is very shallow. Reasons for the shallowness of Inland Drainage (Lake Chad) Nature of the rivers flowing into the lake: The five rivers that supply the lake with water are shallow, flow sluggishly and pass through semi desert. Hence, most of the water is lost through evaporation and percolation into soil leading to reduced flow of water into the lake. Tapping of some rivers by river Benue: Specific Rivers like River Lagone (outside Nigeria) is being tapped by the Benue headstream. This contributes to reduced volume of water. Location of the lake: The Lake is essentially located in Sahara desert and thus it experiences high evaporation leading to low volume of water. Underground drainage: It has been suspected that Lake Chad is experiencing underground seepage to nearby oasis, hence, the shallowness of the lake. Importance of Lakes Employment. Provision of food e.g. fish. Irrigation. Generation of H.E.P. Development of the area. Industrial uses. Transportation. Tourism. Domestic uses.
Relief refers to the surface features of the land above the sea level. Relief of Nigeria can be grouped into two main classes which are lowlands and highlands. Lowlands: Lowlands refer to the areas below 300m above the sea level. Areas of Lowland in Nigeria and their Altitude or Height The Sokoto plain in the North West (200 – 300m). The Niger-Benue trough/valley (100 – 300m). The Chad basin or Borno plain (100 – 300m). The Niger Delta (0 – 100m). The Cross River basin (120 – 180m). The interior coastal lowland of Western Nigeria (100 – 300m). The coastal plain (0 – 100m). Rocks Associated with Lowlands Coastal plain: Sedimentary rocks of alluvial deposits. Niger-Benue trough: Sedimentary rocks of limestone, sandstone and shale. Sokoto plain: Sand, clay, sandstone and limestone. Chad basin: Made up of sand and clay. Rocks generally known to be associated with lowlands are the sedimentary rocks. Importance of Lowlands Plains, especially level ones are good for human habitation. Population and settlements are usually concentrated on plains. Some plains are rich sources of minerals like petroleum and coal. Plains, especially depositional plains have rich fertile soils which favour intensive agriculture. Plains, generally favour communication as roads, railway, and airports are better built on levelled lands. In areas of low rainfall, rearing of animals is carried out in plains as it favours the growth of pasture. Rivers in plain provide water for drinking and transportation. Rivers in plains (basins) provide jobs e.g. fishing. Disadvantages of Plains Some plains, especially in delta areas may be flooded with water and this reduces human activities. Some may pose serious barrier to communication, especially in areas flooded by excess water either from river or after rain. It, therefore, increases the cost of developing these areas e.g. construction of flyovers. Highlands: Highlands refer to areas over 300m above the sea level. Areas of highlands in Nigeria and their height or altitude The highlands in Nigeria are grouped into four areas. These are: The North-Central Highlands: It lies in the centre of Northern Nigeria around Kano, Kaduna, Bauchi, Jigawa and Plateau States. Jos Plateau (200 – 1500m) is found in this highland and is a great hydrological centre or watershed with radial pattern of drainage in which rivers like Hadeija, Kaduna, Sokoto, etc. take their sources. The highest point of Jos Plateau is Shere Hills (1650m). The Western Highlands: The Western Highlands or upland is found in the western part of Nigeria around Ondo, Oyo, Kwara and Osun States. Important hills in this area include: Idanre hill (highest point) – 950m, Apata hill (400 – 700m), Epeme hill (350 – 600m). Three important rivers – rivers Ogun, Osun and Osse have their sources from these highlands. The Eastern Highlands: These are found in the borders between Nigeria and Cameroun. They represent the highest zone in Nigeria. Among the mountains are: Mandara mountain (1200 – 1500m), Biu Plateau (800 – 1000), Adamawa mountain (1800 – 2400m), Alantika and Shebshi hills (1600 – 2000m), Obudu and Oban hills (1200m). The area has rivers like Rivers Gana, Ngoda and Yedseram which flow to Lake Chad. The Eastern Scarpland: This is found within the eastern region of Nigeria, especially around Enugu and Nsukka. The major highland in this area is the Udi-Nsukka Plateau (300 – 600m). Rivers Anambra, Imo and Cross have their sources from this scarpland. Major Rock types in Highlands North central plateau, western highlands, Mandara Mountains, Shebsh, Alantika, Obudu and Oban hills are made up of basement complex rocks (combination of igneous and metamorphic rocks). Jos Plateau is made up of volcanic rocks. Udi Hills are made up of carboniferous sedimentary rocks. Importance of Highlands Some mountains are sources of some minerals like tin, gold, diamond, etc. which are useful to man. High mountains aid the formation of rainfall (Orographic or relief rainfall), especially on the windward side of the mountain. Some low mountains provide pasture which aid transhumance which is the practice whereby cattle move from the valley during rainy season to highlands where they feed on pasture till the end of the rainy season, after which they return to the valley. Some mountains serve as climate barriers because; their two sides may have different climates. Mountains are useful in times of inter-tribal wars for easy defense against enemies. Some high mountains are centres for tourist attraction. Mountains are the sources (the beginning) of many rivers and streams. The nature of some rivers with their steep slopes, fast flowing and presence of rapids at the source aid the construction of H.E.P to generate electricity. Some mountains, as a result of their location do serve as wind breaks. Disadvantages of Mountains Mountains are barriers to communication as they prevent road, railway and airport construction. High mountains are known to be associated with cold weather which prevents good human and animal habitation. Areas close to mountains are usually associated with soil erosion due to the speed to running water down the steep slopes of mountains. Mountains at times do occupy good land that would have been used either for farming or settlement. Mountainous areas are not good for agriculture as the soils are poor in nutrients and difficult to work on.
LOCATION: Nigeria lies within latitude 4˚N – 14˚N of the equator and longitude 3˚E – 15˚E of the Greenwich Meridian. It therefore follows that Nigeria has a latitudinal stretch of 10˚ and longitudinal extent of 12˚. POSITION: Nigeria is in West Africa. She is bounded in the west by Benin Republic, in the north by Niger Republic, in the east by Cameroun Republic, in the north-east by Chad Republic and in the south by Atlantic Ocean. SIZE: Nigeria is the fourth largest country in West Africa in terms of land area after Niger, Mali and Mauritania. The total land area of Nigeria is approximately 923,768 square kilometers. The greatest distance from east to west is approximately 1,300km while from north to south is about 1,100km. In terms of population, Nigeria is the most populous single country in Africa with 140 million (i.e. 140,003,543) people in 2006. Hence, she is often referred to as “the giant of Africa”. POLITICAL DIVISION: The country Nigeria came into existence in 1914 as a result of the amalgamation of the Northern and Southern protectorates. She became independent in 1960. As at independence, the country had three regions namely, North, East and West. The Northern region had its headquarters in Kaduna, East in Enugu and West in Ibadan. In 1963, Nigeria became a Republic and the fourth region known as Mid-West was created from the then Western region with its headquarters in Benin City. The political divisions remained four until 1967 when the country was further divided into twelve states. In 1976, the country was further divided into 19 states. In September 23rd 1987, two more states were created, making the total number to be 21. Nigeria presently has thirty six states and a Federal Capital Territory (FCT), Abuja which is the federal capital of Nigeria.