Introduction
There is nothing in the whole of nature which is more important than or deserves as much attention as the soil. Truly, it is the soil that makes the world a friendly environment for mankind. It is the soil which nourishes and provides for the whole of nature: the whole of creation depends on the soil which is the ultimate foundation of our existence. Natural resources which man is expected to protect are lost because of human ability to alter the natural state of the environment.
The environment today is in a dynamic state due to man’s various activities, but because he cannot be separated from the environment, he goes about his routine lifestyle struggling for survival. These various activities of man have lead to degradation and soil erosion which destroys lives and properties in various parts of the world. This is to say that without plant, life cannot be sustained and without land, man cannot survive.
Umoru (2001) observed that man has contributed to this problem in many ways by constructing road without drainage system, resulting in the washing away of the top soil, flooding etc. Soil erosion is a major environmental threat to the sustainability and production capacity of agriculture. Land erosion has lead to the pollution of water bodies meant for drinking and other domestic purposes. Sometimes erosion washes some poisonous chemicals deposited by man in his environment thereby killing some aquatic lives that are meant for human consumption.
Therefore in other to check the problem of land erosion in man’s environment, efforts should be made, using the available and affordable materials to study and access the prevailing situation so as to provide a scientific, satisfactory and lasting solution to avert its health implication.
Definition of soil erosion
Erosion is a process whereby the soil particles are detached and transported by wind, water and gravity to a down slope or downstream. Encyclopedia Americana in its 2004 edition, defines soil erosion as the wearing away and removal of soil and rock fragment at the surface of the earth by wind, water, ice or other natural agents.
According to Umoru (2001) erosion is the wearing away of the land surface by various natural agent such as water (e.g. sea, river rain) ice and wind. It is the wearing away of the top layer of the earth crust through the action of wind, flooding rain etc. Erosion is a gravity driven process that moves solids (sediments, soil, rocks and other particles) in the natural environment or their source and deposit them elsewhere.
From the foregoing definitions, it is clear that the effects of soil erosion are devastating to the environment. There is therefore the need for soil use to be planned and managed for it to continue to support man’s existence.
Causes of soil erosion
In Nigeria various factors are contributing to soil erosion. Olemeforo and Obasi (1996) opine that the causes of erosion may be classified into two:
- Physical and natural factors
- Man—induced causes.
However, none of the above factors is naturally exclusive in its operation or operates in isolation without the other, rather both factors operates together in most places where soil erosion is identified. Among the physical factors, the following sub-factors are often identified.
- The characters and structure of rock
- The angles of slope
- The soil debris cover or lithology
- Climate
- Hydro geological condition
- Flood and Topography
In most cases, these factors only work to speed — up or accelerate the erosion process through bad agricultural practice, deforestation and bad construction habit of man. According to Ojebor and Ilayah (1999), human activities which have accelerated soil erosion in Nigeria include;
- Wrong crops cultivation or agronomy practices
- Quarrying and some other mining operation
- Road construction without provision for drainage system
- Deforestation
- Use of footpath, over grazing, tramping by livestock and uncontrolled bush burning.
Umoru (2001) opined that coastal erosion may be caused by the following factors:
- Removal of sand from the beach
- Heavy rainfall
- Blockage of drain and leads of drainage channels.
Effects of soil erosion
According to Ojugbeli (2004), to identify water pollution, it is good to know the source of water supply and types of water with all that brings about water borne diseases, which are dangerous to health of man such as typhoid fever, cholera, etc. The effects of soil erosion thus include;
- Reduction of nutrient in the soil.
- Destruction of feeder road
- Unwanted spending of money through the relocation of people who live near erosion places.
- It leads to death of man and livestock, due to drawing of erosion channel.
- Obstruction in water transportation
Health hazards that are associated with soil erosion
- Flooding: According to Olemeforo (1999), the term flooding as a situation where a river channel is inadequate to accommodate discharge from the catchments. Flooding has become a common feature in all the geographical region of Nigeria in recent time as well as other part of African and the entire world.
- Disease infestation: Erosion and its association pollution and dirt (refuse), have been veritable actors in the spread of infestation of diseases. The pollution of water by soil erosion has consequently made water to be unfit for human consumption. So lat any attempt made by using the polluted water is always resulting to disease infestation.
- Physical disaster: Erosion in Nigeria and beyond has caused a lot of physical disasters. Examples include the collapse of Bagade Dam near Kano as reported in National Concord of August 19, 1988; in which 18,000 houses were destroyed and over 10,000 people were rendered homeless and similar incidence also occurred in Ibadan where 30 people lost their lives and 10 houses destroyed about 15,000 people homeless.
Control measures to soil erosion
- Health education to the public on the harmful effects of erosion.
- Use of environmental laws
- Controlled grazing of land
- Making ridges and cross slopes
- Planting cover crops such as legumes, melon and cowpea
- The cutting of steps in hillsides to reduce the velocity of water running down the hill slope.
- The use of urban water plan e.g. Ibadan and Lagos States.
Olatunji (2000) comments that environmental education should be introduced into school curriculum especially at primary and secondary level, that this will enhance the effectiveness of regulatory body in the control of the quality of the environment. This will help to create control of the quality of the environmental problems. Jeered (1997) opined that erosion is sometimes difficult to control because of insufficient tools, labour force and poor planning strategies but proper town planning through the help of town planners will help to control erosion.
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