GEOG 314: Regional Geography of West Africa with special reference to GhanaPhysical FeaturesWest Africa is one of the major geographical regions of Africa. It lies between the Gulf of Guinea in the south and the southern boundaries of the Sahara in the north. It is bounded in west by the Atlantic Ocean and in the east by the Mandara Adamawa-Cameroon Highlands. It covers an area of nearly 6.5 million km2 or about two-thirds the size of the United States of America. The northern boundary is less clearly defined and is generally considered to follow the southern limit of the Sahara Desert. Geological Structure: The geological structure of the West Africa sub-region is made of some parts that were folded more than 1500 million years ago, and some around 1200 million years ago. The part that experienced folding earlier is called regions of cratons and contains most of the sub-regions gold, diamonds, asbestos and iron. The other part that experienced folding relatively recently are called regions of orogenesis and contain most of the sub-regions copper, lead, zinc, and tin.ReliefWest African Coast: The coast varies in character with the seafloor increasing in depth very slowly off-shore. Generally, the coastline of West Africa is low and sandy, and its smoothness is as a result of sand bar deposition, especially along the coast of Togo, Benin and Nigeria. There are very few natural harbours (notable example is the Freetown Harbour). There are smooth cliffs at Cape Palmas and Cape Three points as a result of the sea cutting steadily farther inland.The Coastal Plain: The coastal plains are not extensive and cover only a relatively small part of the sub-region; they are narrowest in the south-west but most extensive in Gambia, Senegal and Mauritania. The coastal plains are hindered inland by plateaus. But there are interior lowlands below the plateaus, such as the drainage basin for Lake Chad.The Plateau: As one moves further inland/northwards from the coastal plain, is the Plateau of West Africa. The surface of the plateaus varies in height / not uniform. There are wide flat surfaces bounded by steep slopes, which are barriers to transport systems. The plateau reaches maximum height on its Western and Eastern extremes. In the west for instance is Futa Jallon plateau and in the east is the Jos plateau. Parts of the plateau have been cut-through by rivers such as Niger and Oti in Ghana.The Highlands: The plateaus are separated in some places by isolated highlands, some of which are volcanic peaks like Guinea Highlands, Bamenda and Cameroon Mountains, the Akuapim-Togo range, the Cameroon-Adamawa highlands.Importance of Relief in West Africa: Generally the relief features promote human sustenance and development. Serves as source of streams and rivers Induces rainfall Provides rocks for construction and related activities Provides minerals from different ecological profiles. avenues for transportation routes Tourists centres.Challenges of Relief: Can impede development especially transport network cause flooding, other natural disaster such as earth quakes

Climatic Characteristics (Temperature and Rainfall)Temperature: Most parts are hot throughout the year. Only a few places have a mean temperature of the coolest month below 200C. Daily temperature is lowest during the rainy seasons due to cloudy conditions and highest during the dry seasons.Rainfall: there are variations in rainfall. The coastal area receives very heavy rainfall esp. from Sierra Leone to southeastern Nigeria (except for a small area around Accra). Moving inland from the Gulf of Guinea, the rainfall decreases in amount, as the rain-bearing winds get further from their source of moisture. Along the Gulf of Guinea coast, rainfall is generally spread out over the whole year but there tends to be two periods of particularly heavy rainfall, separated by two rather drier periods.The position of the Inter-Tropical-Convergence-Zone (ITCZ) explains why there are variations in the amount and seasonal distribution of rainfall. The ITCZ is the zone where the south-westerlies and the northeast trade winds meet. These two seasonal winds dominate the climate of the region. Between June and July, the ITCZ is situated about 170N and 200N, and most parts in West Africa come under the influence of the moist South-Westerlies and so receive rainfall. Between December and January, ITCZ is situated not far from the Gulf of Guinea. Rainfall occurs over the Gulf of Guinea coastlands due to the influence of the south-westerlies. But the rest of the region comes under the dry influence of north-east trade wind. Major Climatic Regions in West Africa These regions conform broadly to patterns of vegetation, soil and fauna. Equatorial Climate: Characterized by heavy rainfall and a dry season that is either short or absent. Temperatures are high, averaging about 250C. Both annual and diurnal (daily) temperature ranges are very low. Examples of places with equatorial climate include Monrovia and Calabar Tropical monsoon : This covers nearly all of Southern West Africa and on the westward coast into Senegal. It has no definite boundary northwards as it merges gradually into Savannah where the dry season becomes longer. Average annual rainfalls amounts are over 2000mm. Temperatures are high all year round averaging 250C.Dry central coastal climate: This has low seasonal and daily temperature ranges. A seasonal change occurs between wet tropical air masses and dry tropical air masses. As a result, there is a very wet season and a very dry season. Savannah climatic zone: This is the most extensive in West Africa. It usually occurs in areas where the dry season is longer than four months. During this season the NorthEast Trade (harmattan) winds blow from the sub tropical high pressure over the Sahara Desert. The most northerly parts experience that for more than nine months of the year. Wet season is between July to September. Temperatures show increasing ranges as one moves north in the region.Desert climates: Desert climates have little and unreliable rainfall. Tropical continental air masses are dominant, with the exception of short periods in summer when brief incursions of moist tropical maritime air bring the possibility of rain.Upland climate: This is a generally cool zone. The Fouta Jallon and Guinea Highlands are areas found in this climatic zone. Climates change rapidly on mountains, becoming colder at higher altitudes. Importance of Climate to the Region: Climate is conducive for agriculture, which is a major source of livelihood for many. However , climate change is posing challenges for the region. Soil Types: Soils in West Africa have been surveyed and mapped under different classification systems. The Soil Taxonomy System developed by the US Dept. of Agriculture and considered to be effective have classified the main soil groups in West Africa as follows:Alfisols: Characterised by a light colour in the upper horizon, low organic matter content and high clay content. They are located mainly in the subhumid to semiarid areas ranging from the forest mosaics to segments of the savannah. Alfisols support a wide range of both cash and food crops such as cocoa, rubber, maize, cassava, millet. Aridisols: Poorly developed with little chemical weathering, infrequent leaching and low organic content. Salinization is widespread resulting in the concentration of mineral salts at the surface. Irrigated aridisols may become infertile as a result of salinization or waterlogging. Nomadic grazing is extensive and crops such as date palm, sorghum and millet are grown on certain parts. Ultisols: Mostly found in moist and subhumid climatic areas under forest conditions and woodlands. Have high levels of chemical weathering and therefore low to moderate organic content infertile. Found mostly in Liberia, Guinea and Sierra Leone and suitable for rubber, coffee and banana plantations (due to the application of modern management techniques).

VegetationTropical rainforest: Occurs along much of the Gulf of Guinea coast but there is a gap in forest around Accra, because of the unusually low rainfall in that area. Has many different species. The very tallest, emergents -grow up to 50 meters in height. Its the habitat for numerous birds and insects. Below the emergents are three layers of plant all competing for sunlight. The top layer or canopy forms an almost continuous cover which absorbs over 70 percent of the light and intercepts 80 percent of the rainfall. The second layer or under-canopy consists of trees growing up to 20metres. The lowest, or shrub layer, consist of shrubs and small trees which are adapted to living in the shade of their taller neighbours. North of the tropical rainforest is the deciduous forest where trees shed leaves during part of the year. There are mangrove swamps along the coast -particularly extensive in the Niger Delta. Savannah Zone: The savannah includes a series of transitions between the rainforest and the desert. The trees in the savannah zone are xerophytic or drought resistant. Long roots, twisted trunks and the bark is usually thick to reduce moisture loss and provide protection from frequent bush fires. The baobab tree and acacia are two of the most common trees found in the savannah. The nature of the vegetation in this zone varies according to the amount of rainfall received and the length and severity of the season. Close to the forest edge, is Guinea savannah- rainfall is moderate and the dry season is not too severe. It consists of a mixture of trees and tall grasses which shed their leaves during the dry season, and the grasses wither and die. Northwards is the Sudan savannah zone where grasses are shorter and there are fewer trees as compared to the Guinea savannah. The Sahel savannah is the most northerly of the savannah zone. Grasses in the Sahel are very short and widely spaced. Thorny bushes are common. Mali and Niger have a large percent of their land in this zone.Desert: Plant life is very scanty with the few adapted to stand very dry conditions. They usually have very small leaves to reduce water loss by transpiration and long roots to reach down to water deep below the surface. Grass is virtually absent from the desert. e.g. northern Mali, Niger and eastern Senegal.

Geographical Regions of West Africa The region diversified in terms of relief, climate, soils and vegetation. Different zones based mainly on the climatic and vegetation belts which run east-west across the sub-region. There is also a North and South difference with a transition zone (Middle Belt) which runs latitudinally and roughly through the middle of the region from east to westThe Climatic and Vegetation ZonesStrand and sandbank vegetation zone: Found on pure sand, just above high water. Usually showered by sea-spray and is always enveloped in moist, salt-laden air. This type of vegetation is well developed on the sand-bar coast of Senegal and the Gulf of Guinea. Herbs, shrubs and grasses are rare. On inward margins poor trees are seen.The high forest regions: The West African mangroves are precisely the same species as those found along the coast of America, but differ from those of East Africa and Indo- Malaysia. Fresh-water swamp forest is wide spread in the Niger Delta, along fresh-water lagoons, rivers and inland swamps. There is an outer fringe of sudd or floating grass, papyrus swamps, mostly found in Nigeria and some other creeks. Species of Raphia and other palms are found inward. This fringing vegetation rarely exceeds 40 feet in height.Lowland Rain Forest is dense with the highest trees sometimes reaching about 200 feet. The trees are highly varied in species, height, and age. Girths of over a yard are common and the trees are typically straight and slender, with few or no branches below the crown. Most barks are thin and smooth, with buttresses extending outwards sometimes from the base of the trunk. There are at least three tiers or layers of this forest with trees between 60 and 120 feet. The uppermost tier usually has a discontinuous canopy but the lowest is a more or less continuous one. Woody climbers are characteristic features. There are the climbers hanging above in great lengths and loops festoons). Numerous epiphyte, mosses and lichens as well as ground herbs are found. Most famous tropical timber is found here in Ivory Coast, Ghana and Nigeria. The zone of cultivation of most cash crops such as cocoa, palm trees, rubber and coffee. Semi- Deciduous or Dry Forest: Found in the equatorial semi-seasonal climatic zone where there are up to four months with less than one inch of rain, lower relative humidity and drier soils. The flora and features are similar to the rest of the lowland rain forest, but has fewer species and canopies may be more open. Shrubs and smaller trees, make woody undergrowth and are mainly evergreen. Deciduous trees may predominate only in the upper storey. e.g. Obeche, Wawa or Samba, Danta, Iroko. Felling of trees (deforestation) has modified the semi-deciduos forest resulting in depleted forest, the secondary forest and derived savannah The Savannah Woodlands: Described as grassland with dispersed trees and shrubs. Sub- divided into the Guinea, Sudan and Sahel Savannahs. Guinea Savannah is found between about 80 and 130 N, and coincides roughly with Southern Savannah climatic zone. Rainfall averages 40-55 inches annually. There are four to five months of the year having less than 1 inch of rain and critical relative humidity may drop to 14 percent. There is also a Presence of grass averaging 5 to 10 feet or more. Trees are fire resistant, even though burnt year after year. The broad-leaved deciduous trees have short boles (stem or trunk), are mostly 40-50 feet high and occur in clumps. Usually have twisted gnarled stems and corky bark, and so are useless for timber. Sudan Savannah: North of the Guinea savannah. Annual rainfall averages about 22-40 inches, there are seven almost rainless months. Relative humidity in early afternoons of dry season may drop to 8 percent. Trees always occur singly, with an average of 25-50 feet in height and have wide-spreading crowns. Egs. Locust bean, Shea tree, Acacia, Kapok and Baobab. Most trees have small leaves, to prevent excessive transpiration, though there are a few broad-leaved ones. Trees also lose all their leaves in the dry season, with the exception of Acacia albida. Grass shoots up only before the rains; it is shorter (3-5 feet), less tussock but more feathery than in the zones to the south. Its very good zone for grazing.Sahel savannah: Occurs in southern Mauritania, north-central Senegal, Mali, southern Niger and the extreme north-east of Nigeria. Has at least 8 dry months. Trees average about 15-30 feet in height, are deciduous, and finely divided in their leaf structure. They have spreading and deeply penetrating roots, which fit the loose sand. The trees are also thorny. E.g. Acacia tree (about 6-12 feet in height). Grasses are short, discontinuous, and wiry and tussock, but much is used by cattle and sheep. Fires are less serious because there is the absence of dense tree cover, high grass cover and population to start them. Montane vegetation: The high areas of West Africa have different vegetation from the coastal and inland lowland. Altitude may modify vegetation because of changes in humidity and cloudiness, rainfall, amount of sunlight, level of temperatures and evaporation. 5