NIGERIA
BACKGROUND INFORMATION
NIGERIA
BACKGROUND INFORMATIONStandard 15
Physical Systems Effects on Human Systems
Introduction
Standard 14 focuses on how humans modify the Nigerian environment. This essay examines the ways in which physical systems impact Nigerian society. While it is somewhat problematic to talk about distinct physical and human systems, this conceptual distinction helps us clarify nature-society interactions. Thus, while the last essay focused on the modifications that humans make to landscapes, ecosystems, and physical systems, this section will focus on the constraints and opportunities that the Nigerian physical environments provide for humans. In particular, I will devote attention to the impacts of climate, topography, and soils on Nigerians. Since climate is central to much of this discussion, a large part of this essay addresses issues related to climatological processes. For related background information on this standard, refer to standards 4, 7, and 8.
Climate
Nigeria has a tropical climate. Because it is located in the low tropics (4-11 degrees north latitude), Nigeria receives relatively constant solar radiation throughout the year. This means that temperatures are relatively warm and constant throughout the year. Nigeria also has a relatively humid climate overall, although this varies substantially from north to south. Rainfall varies seasonally. All of these aspects of climate have consequences for the organization of human activities. This section examines some of the more direct and immediate relationships between climate and Nigerian society. For example, relationships between climate and agriculture, health, and clothing styles are examined. In later sections, indirect effects of climate will also be discussed.
Agriculture is one human activity that is closely related to climate. While some crops can be grown in a wide range of climates, many other crops require more specific growing conditions. Soybeans, for example, are a crop that can be grown in many different climates. In contrast, potatoes can only be grown in relatively restricted areas. In Nigeria, the distribution of agricultural crops is highly influenced by climate. Tubers like cassava and yams are only grown in the southern part of the country where precipitation is sufficient to support these crops. Semi-arid grains like millet and sorghum are only grown in northern Nigeria where precipitation is low to moderate. Many other crops cannot be grown in most of Nigeria because of the warm year-round temperatures or the tropical pests that the climate encourages. In this category are many temperate fruits and vegetables that can readily be grown in the United States and other temperate regions.
The nature of rainfall also impacts the way that crops are grown. Rains in Nigeria are often torrential in nature. Heavy rains can be highly detrimental to crops, however. Because of this, farmers have developed cultivation techniques that are suited to Nigeria’s hard rains. Two examples are high plant mounds and intercropped plant layering. High plant mounds are simply small, human-made heaps of soil that protect plants from erosion and runoff. Although the construction of these mounds involves a great deal of human labor, the benefits are substantial. The intercropping strategy defends plants and soil in a different way. By interplanting different crops in the same field, farmers can "layer their plants to provide defense against heavy rains. On the top layer of the field, a farmer might plant a broad-leaved plant like the cocoyam. Below this he or she might plant smaller plants that are more vulnerable to heavy rains. Thus, the broad-leaved plant can protect both the soil and lower layer plants at the same time.
The seasonal distribution of rainfall is also critical for Nigerian agriculture generally. While tropical temperatures allow for year-round crop production, seasonally concentrated rainfall limits the amount of agriculture that can occur in the dry season. This is not to say that agriculture does not occur in the dry season. In some areas, irrigation is utilized to produce a second or even a third annual crop. Irrigation use is not widespread throughout the country, however. In the northern half of the country in particular, farmers remain limited to a single annual crop that coincides with the rainy season. This seasonality of farm work provides rhythm to rural life in many parts of the country. It is in the dry season that household tasks like roof mending and mud wall repair are performed. Members of rural households also perform supplemental work like craft production, leather working, or migrant urban labor in the dry season. The seasonal distribution of rainfall also impacts the activities of many Nigerian herders. Many Fulani pastoralists move southward with the onset of the eight-month dry season. Since the rainy season lasts longer the farther one moves south, pastoralists find greener pastures if they move into the Middle Belt region of Nigeria.
The combination of high rainfall and warm temperatures has another substantial influence on much of Nigeria’s agriculture. Hot, humid climate provides an ideal habitat for many harmful agricultural pests. Insects are among the most important of these pests. Unlike temperate parts of the world that experience cold temperatures part of the year, tropical regions never experience pest-killing cold temperatures. Thus, while many Americans grumble about the thought of winter, they often forget the agricultural disadvantages that tropical environments face. This is not to say that Nigerians are defenseless against tropical pests, only that they are forced to deal with environmental conditions different from other parts of the world. The next section deals with the relationships between tropical insects and human and livestock health.
As the examples below indicate, many tropical diseases in Africa are related to the presence of water. Many diseases that affect Africans are spread by mosquitoes, which breed near water. "Malaria, for example, is transmitted by various species of mosquitoes which breed close to stagnant or slow-moving water." Malaria is one of the most widespread of all African diseases. Binns estimates that roughly 200 million Africans had malaria in the early 1990s. Dengue fever and yellow fever are two other diseases transmitted by mosquitoes. While attempts have been made to eradicate these diseases, these attempts have only met with limited success. Mosquitoes sometimes become resistant to insecticides. Malaria strains have also become resistant to vaccinations and medicines. In many ways, the surest way to reduce the occurrence of these debilitating diseases is to destroy the habitat of mosquitoes. This requires the draining of wetlands and swamps, which serve as breeding grounds for the mosquitoes. In a country of abundant seasonal rainfall, however, such a task is a daunting one.
Schistosomiasis, also known of bilharzia, is another water-borne disease that affects thousands of people in Nigeria and in Africa. This disease, which weakens the human immune system, is transmitted through snails. The larva that causes the disease depends on snails for the completion of its lifecycle. After leaving the snail, the larva penetrates human skin, typically through the feet or the legs. Interestingly, humans have facilitated the spread of bilharzia through the development of irrigation projects. Canals and flooded fields are prime habitats for the flourishing of bilharzia. Thus, while irrigation development offers benefits for agricultural production, it also has real drawbacks like the spread of bilharzia.
River blindness, transmitted by the black fly, is a disease that causes blindness in humans. The black fly is most commonly found along rivers, especially in rocky stretches with rapids. While African governments have devoted some resources to spraying, river blindness continues to affect many people throughout Africa.
Another fly, the tsetse fly is a pest to both humans and animals. This insect transmits an illness known as sleeping sickness to humans. The name of this illness is highly descriptive of its effects; humans become very sluggish and fatigued after they contract the disease. In animals, the tsetse fly transmits the disease known as trypanosomiasis. As noted in an earlier section, this disease is deadly to certain kinds of cattle. In Nigeria, zebu cattle are the hardest hit by this pest. The tsetse fly inhabits Nigeria’s dense savannas and rain forests. Because of this, the tsetse fly has had important impacts on human settlement and economy in central and southern Nigeria. Humans, and particularly zebu cattle, find it difficult to survive in areas infested with the tsetse fly. Thus, most cattle are found in the northern part of the country where the tsetse fly is not found.
The locust, which is a large grasshopper, is another pest that has historically been important in African agriculture. This pest is also related to water, or rather lack of water. During periods of drought, locusts are often a serious problem for many farmers in northern Nigeria in particular. Thus, this pest compounds farming difficulties associated with low rainfall by destroying crops.
While northern Nigeria experiences a long dry season every year, longer periods of drought sometimes occur in this part of the country. Droughts that occur in northern Nigeria are particularly damaging because of the region’s relatively high population density. Droughts can also be quite damaging because most rural households are semi-subsistence in nature. Thus, if they are unable to depend on their own crops or cattle for food, famine may result. And, although Nigeria has not suffered as severely from famine as other African countries in the last few decades, the threat of famine is always a possibility. Famine is not strictly caused by climatic changes, however. Human systems maintain different levels of vulnerability for various groups within society. Thus, when drought strikes northern Nigeria, people in different situations have varying capacities to deal with it. For example, herders with large stocks of cattle may be able to endure a severe drought if they can keep a sizable portion of their herd alive. Pastoralists with smaller herds will likely be more vulnerable to the impacts of reduced rainfall.
An interesting case study of drought and long-term rainfall fluctuation is Lake Chad. Nigeria borders this large but shrinking body of water on the lake’s southwest quarter. Because of the lake’s shallow depth, low rainfall levels in the last thirty years and hydro-development by Cameroon have substantially reduced the lake’s geographic area. While this has impacted the country of Chad more than Nigeria, many pastoralists and marginal farmers have been dramatically impacted by long-term changes in the size of Lake Chad.
The examples thus far have focused primarily on climate’s impact on agriculture. Other aspects of Nigerian society are impacted by the country’s unique climates. As noted above, Nigeria’s heavy rains influence the way that agriculture is conducted. Torrential rains also create challenges for other areas of life. The most pervasive problem related to heavy rains is erosion. Erosion not only affects farmers, it also impacts the built environments of humans. For example, many roads are seriously impacted by Nigeria’s heavy rains. In many parts of the country, it is difficult to maintain roads because of the ravages of the rainy season. Roadways with poor drainage often experience erosion and surface damage. This occurs when water erodes the soil underneath paved roads. After this lower soil layer is eroded, pavement collapses and crumbles away. In many rural areas, roads are so bad that vehicles are forced to create new paths around damaged roadway. A similar process affects many buildings and residences in villages or cities. In areas without adequate drainage infrastructure, water can quickly erode a household’s front yard or building foundation. Many cities do have drainage ditches, but these can sometimes be clogged with trash or debris, making them less effective in preventing erosion and other sanitation problems.
Another important aspect of Nigeria’s climate is the dry-season phenomenon of the harmattan. These are hot, dusty winds that originate in the Sahara Desert to the north. These winds are particularly important in the northern half of the country where the dry season is longer and there are fewer trees to impede the winds. The harmattan winds create many daily challenges for humans. One of the most basic is that they make it difficult to keep things clean. Dry, reddish dust coats human bodies, furniture, books, and walls. Even after the rainy season brings an end to the annual harmattan experience, the lingering dust of the winds is easy to find. These frustrations are compounded by the fact that most buildings do not have tightly sealing windows. This is due to Nigeria’s warm temperatures. Thus, while semi-open buildings improve internal climate control, they also allow the dust of the harmattan to invade building openings. Another example of harmattan effects is machine maintenance. Since most engines and other machines require adequate lubrication to function properly, it is important that dirt and dust not get inside machinery. Harmattan conditions, however, make machinery maintenance more challenging than it would otherwise be.
I will close this section on climate by examining another consequence of warm year-round temperatures. It was already noted above that warm temperatures influence architecture in Nigeria. Temperature also influences clothing preferences. One important example is footwear. The majority of Nigerians wear sandals or "slippers" on a daily basis. This type of footwear is only suited for a relatively warm climate. Many Nigerians, especially in the North, also wear clothing that is adapted to the warm climate. Theirs is not the American dress of shorts and tee shirts, however. Customary northern dress is long flowing outfits for both men and women. As the contrast with American fashion illustrates, climate influences fashion but it does not determine fashion. That is left to human choice.
Topography
This section examines the influence of topography on Nigerian society. Although the impacts of topography are perhaps less immediate than those of climate, they are important nonetheless. In several of the points mentioned here, the enabling aspects of Nigeria’s topography are emphasized. Before we begin this discussion, however, it is important to review the basic characteristics of Nigeria’s topography. As the maps show, Nigeria is a country with no high mountains. And, aside for the north-central highlands, the eastern highlands, and the western highlands, most of Nigeria is plains. This fact is important for many different reasons.
First, relatively low elevation means that topography has less impact on climate. Orographic precipitation and adiabatic cooling are relatively insignificant in Nigeria. This is important because it reduces climatic variability in Nigeria. And, as was seen in the previous section, climate has an important role in what crops can be grown in a particular region. In some parts of tropical Africa (e.g. Kenya, Rwanda, Burundi), more temperate crops like coffee can be grown in areas of higher elevation. Except for the Jos Plateau and selected other parts of Nigeria, more temperate crops cannot be grown. Second, an abundance of plains and lowlands means that vast areas of arable cropland are available. Third, lowland areas also facilitate easier movement of people and goods. Fourth, topography has had relatively less influence on human settlement patterns in Nigeria. People tend to settle in particular places for reasons other than good topography. These might include good water or fertile soil. One area that has impeded human settlement, however, is the coastal swamps. Since well-drained land is scarce in these areas, agriculture has been limited. Instead, many people of the Niger Delta and other swamplands have depended on fishing for many of their subsistence and commercial needs. Swampy areas have also been difficult places to establish houses. Like other parts of the world, many stilted houses can be found in the coastal swamps.
Another simple but important impact of topography is river flow. Since rivers flow from high to low altitude, the nature of a region’s topography is a key determinant of its hydrology. In the case of Nigeria, West Africa’s largest river flows through Nigeria because of the unique physical relief of Nigeria and its neighboring countries to the west. It is very peculiar indeed that the source of the Niger River is in Guinea, a coastal country due east of Nigeria. Because of this peculiar course, Nigeria experiences the benefits and the challenges of having one of the world’s largest rivers pass through much of its territory. Because of Nigeria’s topography, however, much of northern Nigeria, and particularly the northeastern quarter, is not contained within the Niger River watershed. Most of this area is contained within the Lake Chad internal drainage basin. Both of these facts present opportunities and challenges for the use of Nigeria’s water resources. One of the most important consequences is that it is not possible to use river transport from much of northern Nigeria to southern Nigeria. Even if topography facilitated this mode of transportation, the prolonged dry season of the North substantially drains rivers of that region.
Vegetation
Vegetation is highly related to climate, soils, and topography. Vegetation is also much more susceptible to human modification than climate and topography. Because of these facts, this section is shorter than the previous two sections. The latter of these two points bears some discussion, however. The concept of "natural vegetation," in particular, needs some clarification. As with most of the world, there are few, if any areas of Nigeria that have not been modified by humans. One of the most modified aspects of the environment is vegetation. For example, many areas of rain forest have been cut. Other forested areas have been selectively logged. In addition, vast portions of the country have been placed under semi-permanent or permanent cultivation. The key point of this section, however, is that different parts of the country favor the growth of certain kinds of plants. Even though humans have modified all of the "natural vegetation" of Nigerian to some degree, human activities are still influenced by the composition and density of vegetation in particular parts of the country. Nowhere is this more evident than the tropical rain forest region of the country. In this region, annual rainfall is the highest in the country. This, coupled with the relatively more even seasonal distribution of rainfall means that overall density of vegetation is much higher in this region. Thus, even in areas where old growth rain forest has been cut down, tall grasses and secondary growth trees are often quick to refill the deforested area. In these areas, land clearing is much more labor intensive relative to the savanna regions to the north. Partly for this reason, many areas of the rain forest region have been converted to oil palm production. Other agricultural crops are often interspersed in these areas. Similar patterns exist in cocoa-growing regions. Thus, instead of clearing the land entirely of trees, farmers choose to selectively maintain certain tree species like the various palm species and the cocoa tree.
Another aspect of vegetation’s influence on human systems is the seasonal nature of vegetation growth. In the northern half of the country, vegetation is brown and relatively sparse during much of the dry season. The landscape is more open and more penetrable. It is this period of the year that farmers burn new fields in the savanna regions. Because trees and plants are dry and brown during this season, the vegetation burns easier. As is discussed in the next essay, this season is also a time of intensified fuelwood collection.
Soils
Soils are also closely related to climate, topography, vegetation, and human modification. Nonetheless, a few points should be made about soils’ influences on Nigerian society. This is a particularly important section since Nigeria relies heavily on agriculture for its economy. Unfortunately, however, Nigeria is not blessed with high quality soils. In this regard, Nigeria is similar to many other countries of sub-Saharan Africa that struggle with poor to average soils. The poor quality of Africa’s soils is partly caused by leaching. Because of heavy rains and serious problems of erosion, many minerals and nutrients are sapped from Africa’s soils. This is one of the main reasons why systems of shifting cultivation or field rotation have been so prominent in many parts of the continent. Thus, without additional fertilizer inputs, agricultural productivity often remains stagnant. In Nigeria, however, poor soil quality is only one of many factors that have served to marginalize many small-scale farmers. Poor government policies and economic crises have also been important in the stagnation of agricultural production. Nonetheless, poor soils constrain the ability of many producers to produce large surpluses.
Conclusion
This essay has emphasized the constraints and opportunities of the Nigerian physical environment. An important point that should be reemphasized is that human activities are not determined by physical systems, only influenced by them. This was clearly indicated in the discussion of climate, topography, vegetation, and soils. Thus, it is important to synthesize the materials found in standards 14, 15, and 16 to maintain a more complex and sophisticated understanding of nature-society relations in Nigeria. While physical systems impact human societies, they are also shaped by human actions. This is clearly the case with vegetation and soils, but less so with systems like climate and topography, global warming and earthmovers notwithstanding.
Web Resources on Physical Systems’ Influence on Humans
Physical Maps
Thematic Physical Geography
