Wednesday, October 30, 2013

Land degradation- Land slides, Soil erosion and Desertification

LAND DEGRADATION
Land degradation is the process of deterioration of soil or loss of fertility of soil.

EFFECTS OF LAND DEGRADATION

  1. Soil texture and structure are deteriorated
  2. Loss of soil fertility due to loss of valuable nutrients
  3. Increase in water logging, salinity, alkalinity and acidity problems
  4. Loss at a social, economic and biodiversity level
CAUSES OF LAND DEGRADATION
Population: With the increase in population, more land is needed for producing food, fibre, and fuel wood leading to increasing pressure on the limited land resources. Therefore the land gets degraded due to over exploitation

Urbanization: Increased urbanization due to population growth reduces the agricultural land. To compensate for loss of agricultural land, new lands comprising of natural ecosystems such as forests are cleared. Therefore, urbanization leads to deforestation which in-turn affects millions of plant and animal species.

Fertilizers and Pesticides: Increased application of fertilizers and pesticides are needed to increase farm output in new lands thereby leading to pollution of land, water and soil degradation.

Damage to top soil: Increase in food production generally leads to damage of top soil through nutrient depletion.

Water-logging, soil erosion, salination and contamination of the soil with industrial waste cause land degradation.

LANDSLIDES
Landslides are the downward movement of a slope composed of earth materials such as rock, soil or artificial fills. Landslides are also called rock-slide, debris-slide, slump, earth-flow or soil-creep. 
During construction of roads and mining activities huge portions of mountainous fragile areas are cut down and thrown into adjacent areas and streams. These land masses weaken the already fragile mountain slopes leading to man-induced landslides.

EFFECTS OF LANDSLIDES:
  1. Landslides increase the turbidity of nearby streams, thereby reducing their productivity
  2. Destruction of communicative links
  3. Loss of habitat and biodiversity
  4. Loss of infrastructure and economic loss
CAUSES OF LANDSLIDES
  1. Removal of vegetation - Deforestation in slopes creates soil erosion leading to landslides
  2. Underground mining activities cause subsidence of the ground
  3. Movement of heavy vehicles in areas with unstable slopes causes landslides.
  4. Addition of weight by construction on slopes causes landslides.
  5. Over exploitation of groundwater also leads to landslides.
SOIL EROSION
Soil erosion is the process of removal of superficial layer of soil. Soil erosion removes soil components and litter.
HARMFUL EFFECTS OF SOIL EROSION

  1. Soil fertility is lost
  2. Loss of soil ability to hold water and sediment
  3. Sediment runoff can pollute water courses and kill aquatic life
TYPES OF SOIL EROSION
  1. Normal erosion: This is caused by the gradual removal of topsoil by natural processes. The rate of erosion is slow.
  2. Accelerated erosion: This is caused by man made activities. In this case, the rate of erosion is much faster than the rate of formation of soil.
CAUSES OF SOIL EROSION
  1. Water: Water affects soil erosion in the form of rain, run-off, rapid flow or wave action
  2. Wind: Wind is an important climate agent that carries away the fine particles of soil thereby contributing to soil erosion.
  3. Biotic agents: Overgrazing, mining and deforestation are the major biotic agents causing soil erosion. These processes disturb the top soil thereby exposing the soil to various physical forces inducing erosion
  4. Landslides cause soil erosion
  5. Construction of dams, buildings and roads removes the protective vegetal cover leading to soil erosion
SOIL CONSERVATION PRACTICES
  1. Conservational till farming or no-till farming: Traditionally, land is ploughed to make a planting surface. This disturbs the soil and makes it susceptible to erosion. The no-till farming method makes minimum disturbance to the top soil by making slits in the unploughed soil. Seeds, fertilizers and water are injected in these slits.
  2. Contour farming: In this method, crops are planted in rows along contours of gently sloped land. Each row acts as a small dam to hold soil thereby slowing water runoff.
  3. Terracing: In this method, steep slopes are converted into a series of broad terraces that run across the contour.This retains water for crops and reduces soil erosion by controlling runoff.
  4. Alley cropping or Agro forestry: This method involves planting crops in strips or alleys between rows of trees or shrubs that provide fruits and fuel wood. Hence, when the crop is harvested, the soil will not be eroded as the trees and shrubs remain on ground holding the soil particles.
  5. Wind breaks or shelter belts: In this technique, trees are planted in long rows along the boundary of cultivated land which block the wind and reduce soil erosion. Wind breaks help in retaining soil moisture, supply wood for fuel and provide habitat for birds.

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