Soil+and+Change

SOIL AND CHANGE Soil refers to the uppermost layer of the Earth crust that support plant life and microbial activities. Soil plays an important role in the functioning of our planet. It is important due to the following reasons:
 * Supports plant life- serves as as source of nutrients for plant life.
 * Serves as a habitat for insects microbes such as bacteria and fungi.
 * Supports wildlife
 * Needed for the foundation of the built environment- building of houses, construction of roads e.t.c
 * Provides natural filtration for water.
 * Serves as a store for carbon and nitrogen
 * Preserves records of ecological and cultural past i.e archaeological sites.
 * Contains essential resources for human use- gold, iron, bauxite e.t.c
 * Induces the hydro-logical cycle- soil serves as a store for water and gives out the water at the same time as a form of evaporation and so on.

Despite the importance of soil, certain human and physical activities contribute to its degradation thereby reducing its quality. **Soil Degradation** Soil Degradation refers to a reduction in the quality and quantity of the soil, through various processes and agents such as wind, water, animals.
 * Physical Degradation:** Physical Degradation is a loss in the structure and permeability of the soil.
 * Biological Degradation:** Biological Degradation is the loss of humus (fertile soil), plant life and animals.
 * Chemical degradation:** Is a reduction in the chemical composition, quality of the soil, or a reaction between soil nutrients and water which determines whether the soil will be alkaline or acidic.

The universal formula for calculating soil degradation or soil erosion.

** Causes of soil Degradation **
There are two main causes of soil degradation:
 * Human Causes
 * Natural causes

Human Causes of soil degradation · **Overgrazing** · Allowing a large number of livestock to graze the land over and over again, thereby making the land susceptible to the agents of soil erosion such as wind and water by · **Deforestation** · The cutting down of trees without replacing them. As population grows there is an increase in the demand for fuel, housing, roads, etc. This leads to the cutting down of trees and the burning of bushes in order to provide land for economic development. · **Overpopulation** · As the world’s population grows above 7 million, there is an increase in the demand of land for agricultural purposes, settlements, industry, road construction, etc. this results in the destruction of forests and other fragile ecosystems such as tundra, Savannah etc. · **Sand winning** · The removal of sand and topsoil in order to provide the material for the construction of building foundations, dams and roads. These materials can be fine sand, laterite, boulders and pebbles. · **Mining/ Quarrying** · Open cast mining, or surface mining, involves leveling large areas of land to provide access to minerals in the earth. · **Over Cultivation** · Over cultivation involves growing of crops and rearing of animals on the same piece of land year after year without allowing the land to fallow. this is because it strips the soil of nutrients and makes it infertile. Eventually, farmers abandon the barren land which is left exposed to wind and rain. · **Toyotarisation** · This is the use of 4-wheeled vehicles, SUV's or heavy duty vehicles to carry large rocks away from mining areas leads to the compaction of the soil, making the surface impermeable to water, increasing surface runoff. This process, over time, leads to the creation of gullies, streams, etc. which further degrade the soil.
 * Physical Causes of Soil Degradation **
 * Global warming: **
 * Increasing global temperatures increase the rate of rainfall which increases the risk of floods. As global temperatures increase, many areas close to arid regions would lose a significant percentage of their soil moisture through excessive evaporation, leading to soil compaction and eventually reduced vegetative cover in some areas. Consequently, wind and other factors affecting soil erosion will remove the top soil, thus making it infertile for agricultural purposes.
 * Flash Floods **
 * Intense periods of rainfall within a short period of time are referred to as flash floods. This removes the top soil, as the water will not have time to infiltrate the soil. There will rather be surface runoff which may lead to galleys and surface runoff.
 * Strong winds **
 * In savannah areas, strong winds during the dry season are capable of removing the topsoil and dust, reducing the quality of the soil.
 * Slope/Topography **
 * Steeper land slope gradients cause greater surface runoff which creates streams and galleys which removes topsoil from highland areas.


 * Environmental effects of soil degradation **
 * 1) Desertification – Through the cutting down of trees, exposure of the topsoil to factors such as rain and wind. As the soil gets degraded, there will be less nutrients to support plant life leading to desertification.
 * 2) leads in the reduction in the moisture content of the soil (aridity)- when the moisture content of the soil through evaporation and surface run-off.
 * 3) Reduction in vegetative cover that will lead to an increase in surface run-off.
 * 4) soil buffering capacity ( ability of the soil to resist change)- Has a direct impact on the global carbon cycle through a reduction of soil organic matter and the release of CO2 into the atmosphere.
 * 5) Famine (severe food shortage) – Due to lack of rainfall due to desertification and poor crop yield due to poor soil due to acid rain, mono culture, erosion etc.
 * 6) shortage of water supply as a result of reduction of rainfall- Leads to drying up of wells and springs, leading to shortage of water for human consumption.
 * 7) Loss of biodiversity i.e Flora, fauna thus affecting the food chains and webs.
 * 8) Development of gullies and sand dunes.

NB: The Study of Soil Degradation in Poor Countries (Page 60 of IB Geography Course Companion) ** Solutions to problems of degradation ** ** Cropping methods ** They deal with the prevention of soil erosion by improving texture/moisture, increasing the amount of humus in the soil and improving the level of Microbial activity by;
 * Socioeconomic effects of soil degradation **
 * 1) High cost of water in urban areas
 * 2) Rural-Urban migration due to rural unemployment resulting from a fall in the reduction of the agricultural activities.
 * 3) Poverty- where there is little or no income due to the fall in crop yield.
 * 4) Higher food prices as result of severe food shortages.
 * 5) Child malnutrition as a brought about by the lack of basic nutrients such as Vitamin A, C e.t.c
 * 6) Rise in conflicts between community- for grazing land and water.
 * 1) Afforestation- Planting of trees to replace lost ones helps to reduce desertification.
 * 2) Mixed cropping- Helps to solve problems associated with over cultivation or mono culture. Mixed cropping release stress on particular nutrients.
 * 3) Planting leguminous plants (beans, nodes, cowpeas) replenishing soil nutrients by increasing the amount of soil in the soil.
 * 4) Leaves prevent splash erosion. Roots of soil helps to improve soil structure and water holding capacity of a soil.
 * 5) Planting of hedgerows to serve as wind breaks- Reduces wind erosion, serves as a habitat for fauna which decomposes and enriches the soil. Roots of hedgerows hold the soil, improve the soil structure to reduce erosion.

** Mechanical methods ** Refers any systems or type of farming that helps reduce soil degradation. 
 * 1) Terracing-leveling of hills and slopes to prevent surface run-off.
 * 2) Shelter/Green belts- planting of trees to serve as barriers to the winds in order to reduce its flow and speed (wind breaks)
 * 3) Contour ploughing- Ploughing around the slope in high land areas in order to increase water retention, infiltration and also reduce surface run-off [[image:terrace-tea.jpg.653x0_q80_crop-smart.jpg width="387" height="262"]] [[image:contourfarm.jpg]][[image:imagebig1052.jpg width="352" height="275"]](Google.com)