The health implication of erosion in urban societies

Introduction

Committee on 21^st Century Systems Agriculture (2010) state that erosion is the process by which soil and rock are removes from the earth’s surface by exogenic processes such as wind or water flow and then transported and deposited in other location.

Excessive erosion in urban societies caused problems such as desertification, decreases in agricultural productivity due to land degradation, sedimentation of water ways and ecological collapse due to loss of the nutrient rich upper soil layers. Water and wind erosion are now the primary causes of land degradation. Combined, they are responsible for 84% degraded acreage, making excessive erosion one of the most serious environmental socio-economic problems affecting urban society.

According to Ramdhir (2007), erosion is usually accelerated by human activities such as forest destruction, traditional agriculture, grazing, construction and mining. Whenever vegetation is removed, as when forest are cleared for agriculture and the ground may increase on sloping land, it far exceeds the rate under natural conditions.

Umoru (2011) observed that man has contributed greatly to this environmental problem in many ways by constructing road without drainage system, indiscriminate disposal of solid waste and also building houses against the wind and water channels resulting to several collapse of buildings, loss of lives and properties including flooding etc. Erosion has being in existence since the evolution of the earth and it has existed for as long as water has been on earth. The bid to maintain a sustainable environment has been the priority of man despite finding means of survival.

Therefore in other to examine and find solution to the problem of 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 satisfactory and lasting solution to avert its health implication.

What is erosion?

According to Ojebor (2009), erosion is the removal of uppermost layer of the earth surface. This process is carried out by agent of denudation e.g. water, wind, wave etc. it has led to flooding which invariably lead to disaster.

Umoru (2011) defines erosion as 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 topmost part of the earth crust.

Erosion is the process by which soil and rock are removed from the earth’s surface by exogenic process such as wind, ice, water, etc. It is part of the process of denudation which besides the wearing away of rock and also involved the transportation and eventually depositing the sediments (Lobb, 2009).

Olemeforo and Obasi (2008) gave their own perspective that soil erosion is one of the most visible land degradation features in Nigeria with; particular reference to the southern and eastern part of Nigeria.

Man due to his quest for survival and also performing his socio-cultural activities has degraded the environment where he lives and it is now increasingly evident that more and more disease form from the degradation caused by man and its environment.

Therefore all over the world, it is now recognize that the use of soil (land) must be planned and that land must be properly managed. It is to continue to support  its (soil) existence, its properties, and livestock and give the maximum yield of crops that can sustain man.

Types of erosion

There are many types of erosion. According to Ajayi (2008), the types of erosion are:

• Mass-movement erosion: When gravity combines with heavy rain or earthquakes, whole slopes turn slum, slip or slide
• Gully erosion: It occurs on unconsolidated sub-soils. These are generally deep and generate a lot of sediment, which often feeds into rivers
• Wind Erosion: The wind can remove the valuable fine soil on the land surface. Seasonally strong winds hit many areas, such as sand dunes, the central volcanic plateau. If covering vegetation has been grazed or disturbed, wind erosion can be severe.
• Fluvial erosion: This occur when running water gouges shallow channels or deep gullies into the soil
• Rill erosion: On sloping land, particularly if cultivated, water runoff may gather in small V-shaped channels or rills
• Sheet erosion: This occur when rain falls on bar or sparely covered soil, loosening fine particles (silt clay and humans that are carried down bill in surface run-off sheet erosion lowers the fertility of the soil, because it removes the most productive layer, which has usually been enriched by fertilizer.
• Tunnel gullying: When water enters the soil on a slope, usually down cracks after a dry period, it scours out the sub-soil to form a tunnel. The soil often later collapse inwards and an open gully forms. Losses soil (fine dust) are very prone to this land of erosion.

Causes of erosion

According to the Committee on 21^st Century Systems Agriculture (2010), erosion is usually accelerated by such human activities as forest destruction, traditional agriculture, grazing, construction and mining. Whenever vegetation is removed, as when forests are cleared for agriculture and the ground is exposed to rainfall, soil erosion by water and wind may increase. On sloping land, it far exceeds the rate under natural condition. Accelerated erosion, widespread throughout the tropics, is one of the most serious environmental and socio-economic problems affecting urban people.

Randhir (2007), observed that the potential for soil erosion increases if the soil has no or very little vegetative cover of plants and/or crop residues. Plant and residue cover protects the soil from raindrop impact and splash, tends to slow down the movement of effectiveness of plant and crop residue depends on the type, extent and quality of cover. Vegetation and residue combinations that completely cover the soil and intercept all falling raindrops cover the soil and intercept all falling raindrops and close to the surface are the most efficient in controlling soil erosion (e.g. forest, permanent grasses partially incorporated residue and residual root are also important as these provide channels that allow surface water to move into the soil.

Lobb (2009) stated that, the two most important climate factors having a direct effect on erosion are precipitation and wind velocity other climate factors have an indirect effect on soil erosion such as water balance, evapo-transpiration, temperature and relative humidity. Indirect factors, affect the erosivity of rainfall by altering the soil moisture regime and the proportion of rainfall that may become surface runoff  for erosion control it is necessary to investigate physical characteristics of rainfall, including the amount, distribution, intensity, energy load, seasonality and variability of rainfall and the formation and course of surface runoff.

Mirsal (2008) stated that, deforestation and other removal of plants play a major role in soil erosion. Without leaves to intercept rainwater, the said quickly becomes situated, speeding up erosion. This also increases he effection of erosion by winds

Topography also influences the amount of erosion the steeper the slope, the easier it is for soil to be washed blown downhill. Also, sandy soil types are more easily eroded than clay-type soils ploughing of fields also make soil much easier to erode

In Nigeria various factors are contributing to erosion. Olemeforo and Obasi (2008) opined that the causes of erosion may be classified into two (2):

1. Physical and natural factors
2. Dull ropogenic or 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 characteristics and structure of rock
• Climate
• Hydro geological condition
• Flood and Topography

According to Ojebor (2009), 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 to mention but a few.

Umoru (2011) 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.

 Health Implication of erosion

Balba (2006) state that, deposits of ended soil may cause infrastructure damages, such as blocking roads and drains. They may also damage houses, road, fences power and phone lines, water ways and aquatic habitats. The increased turbidity (cloudiness) of water reduces the amount of light that can penetrate. This adversely affects fish diversity, food supply and use of water ways for recreation.

According to Ritter (2006), soil erosion (especially from agricultural activities) is considered to be the leading global cause of diffuse water pollution, due to the effects of the excess sediments flowing into the world’s water ways. The sediments, as well as being carriers for other pollution, such as attached pesticide molecules heavy metals. The effects of increased sediments loads on aquatic ecosystems can be catastrophic, silt can smoothen the spawing beds of fish, by filling in the space, between gravel on the stream bed. It also reduces their food supply and causes major respiratory issues them as sediment enters their gills. The biodiversity of aquatic plant and algal life is reduced and invertebrates are also unable to survive and reproduce. While the sedimentation event itself might be relatively short-lived the ecological disruption caused by the mass die off often persists long into the future.

According to Ichide (2008) the health hazards associated with erosion are:

• Disease infestation
• Flood
• Physical disaster

1. 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 any attempt made by using the polluted water is always resulting to disease infestation.
2. Flooding: According to Olemeforo and Obasi (2009), the term flooding can be described 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.

• 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. A global record of devastating effect of erosion has been kept. In November, 1999, it was reported by Guardian News paper that erosion in Vietnam devastated the central province of the region and about 550 people lost their lives and properties worth 200 million dollars.

Control of erosion

According to Jones (2008), erosion control is the practice of preventing or controlling wind or water erosion in agriculture, land development and construction. Effective erosion controls are important techniques in preveting water pollution and soil loss. The control often involves the creation of a physical barrier such as vegetation or rock, to absorb some of the energy of the win or water that is causing the erosion. On construction sites, they are often implemented in conjunction with sediment controls such as sediment basins and silt fences. Bank erosion is a natural process. Without it, rivers would not meander and charge course.

Blanco (2010) stated that, changes in the cropping pattern that will help reduce soil movement include intercropping, alley farming, use of grass strips and pasture improvement for example, conversion of cultivated land to grassland can reduce erosion by at least 10 percent. Producing feed crops for livestock presents an opportunity to integrate animal husbandry and erosion control. Producing sufficient fodder grasses reduced the need to grazing animals. Cutting and faming feed may reduce crops land. Alternating strips of protected plants (vegetables) with protective plants (fodders grasses) will trap suspended partials and reduce soil movement. It must be noted that the use of protective grass strips is effective only if grazing is avoided. Crop rotation helps to preserve soil fertility. A rotation of one year of grain millet, etc. followed by three to four years of legume pasture may be an excellent alternative to shifting cultivation.

Ojewale (2009) said that there is need to protect health and environment, to minimize the burden of future generations and that government should intensify environmental education more than ever before, to curb environmental degradation, destruction, distraction and disruption resulting in land erosion desertification and other natural health hazards and risk. These include the following:

• Health education to the public on the harmful effects of erosion.
• Making ridges and cross slopes
• Controlling overgrazing of lands
• Use of environmental laws and policies
• Planting cover crops such as legumes, melon and cowpea
• Fallowing of farmland should be encouraged
• The construction of drainage system in the area that needed drainage which will help to facilitate easy flow of water.
• Orientation of the inhabitants on how to dispose their refuse.
• The potential dredging of the river.
• The establishment or environment monitoring group in the area.
• Provision of refuse bins and dump sites for the disposal of waste

Conclusion

Soil erosion which is the gradual washing away of the topsoil, which occurs either due to effect of rainfall or action of wind with its associated health implications on human health and the immediate environment. Erosion is a major source of land degradation, harmful air-borne diseases and poor yield of crops which leads to nutrient deficiency.

Recommendations

Based the above-named heath implications of erosion, the following are recommended:

1. Physical barrier should be created using vegetation or rock to absorb some of the energy of the wind or water responsible for the erosion.
2. There should be change in cropping pattern such as intercropping, alley farming, use of grass strips and pasture improvement.

• The government should try as much as possible to construct drainage system to help prevent the occurrence of gulley as the water finds a means of exit.
• People should be encouraged to cultivate a maintenance culture by cleaning blocked drainage system.

References

Ajayi, P.O. (2008). Comprehensive geography for senior secondary school. Benin: Johnson A.

Balba, A. (2005). Desertification: wind erosion management of problem soil in and arid ecosystem. Australia: CRC Press.

Blanco, H. & Rattam, L. (2010). Wind erosion: Principles of soil conservation and management. London: Springer

Committee on 21^st Century Systems Agriculture (2010). Towards sustainable agriculture system in 21^st century. Washington: Academic Press.

Jones, B., Hinkel, K. & Eisner, W. (2008). Modern erosion rates and loss of coastal features and sites. Beaufort sea coastline, Alaska: Arctic institute of North American.

Lobb, D. (2009). Soil movement by tillage and other agricultural activities. New York: MIT Press.

Mirsal, I. (2008). Soil degradation, soil pollution: origin, monitoring & remediation. London: John Wilet & Sons.

Ojewale, S.A. (2009): Challenges in primary health care implementation, EHOAN Conference Paper on August 13, 2009 at University of Ibadan, Oyo State, Nigeria.

Olemefere N. C. & Obasi O. E. (2008): Environmental protection Nigerian focus. Lagos: Achugo.

Randhir, T. (2007). Watershed management: Issues and approaches. Washington D.C: IWA

Ritter, M. (2006). Geologic work of streams: The physical environment an introduction to physical geography. Wisconsin: University Press.

Umoru, A. (2011). A protective of environmental pollution. Cambridge: University Press.