Tuesday, September 9, 2014

Natural resources - Land resources


Human and natural activities need space for their location and development. This space is provided by land which is put to various uses like food and energy production, waste-disposal, industrial, commercial and residential purposes.

Land houses the living species, water resources and raw material resources (minerals and ores).
Pattern of land use on earth is:
Arable land
Land for pastures and meadows
Forest land
Urban land and
Non-agricultural land

Land-use involves economic activities leading to environmental problems like:
Pollutant discharge
Waste disposal
Consumption of natural resources for economic activity
Disturbing ecological cycles and wildlife habitats

Changes within a particular land-use category result in major changes in landscape thereby reducing its capacity support a diversified and balanced wildlife. This reduces tourist and recreational value. Ultimately this results in reduced potential for multiple use of these areas. Land being used for one purpose may be used for another purpose. The following examples are listed:
Agricultural land might be used as an urban area
Agricultural land may be used for forestry
Forest land may be cleared for agricultural purposes

Significant negative effects are seen on the environmental quality as a result of the above listed land use changes:
Impact on water cycle
Impact on ground and surface water
Emission of water pollutants
Emission of air pollutants
Destruction of wildlife due to habitat destruction
Degradation of soil

List of environmental conflicts between adjacent land owners
Residential areas located near industrial areas are affected due to air pollution due to effluents due to effluents of energy and industrial effluents.

Residential areas located near airports and along highways and motorways suffer from nuisance due to air pollution

Intensive live-stock breeding units are a source of offensive odours to nearby dwellers

Development of linear infrastructure (roads and railway tracks) in rural areas affects existing land-use as well as natural ecosystems (forests, etc)

The surface layer of land is called soil. 
Fertility or productive capacity of the soil depends on the minerals it contains. 
Minerals are mainly available to the top layer of the soil. Hence, the top layer is the best for vegetation.

Land degradation refers to deforestation or deterioration or loss of fertility or productive capacity of soil. The factors contributing to land degradation are listed below and discussed subsequently.

Soil erosion
Soil pollution
Salination and water logging
Shifting cultivation

Soil erosion is the loss or removal of the superficial layer of soil by the action of water, wind or human activities. Factors influencing the extent of soil erosion are:
Distribution, intensity and amount of rainfall:
Unequal distribution of rainfall results in heavy rainfall being restricted to a few months. The soil unable to absorb this heavy rainfall causes run-off water that removes layers of soil as it moves, resulting in soil erosion.
Slope of the ground: Steep slopes cause decreased infiltration and increased run-off resulting in more soil erosion.
Nature of the soil: Light, open soils lose more silt than heavier soils (loam) that swell-up by wetting.
Vegetation cover: Vegetation holds the soil in place by forming a network of roots of plants. Rainfall on thick vegetation causes negligible soil erosion. Rain falling on bare land causes soil erosion as top soil is loose.
Soil mismanagement: The following techniques listed below contribute to soil mismanagement:
Faulty methods of soil drainage
Wrong methods of cultivation
Forest fires and
Removal of forest litter are common practices that aggravate soil erosion.
Erosion, floods and sedimentation result in deposition of silt and consequent clogging of irrigation canals.

Soil pollution: Soil pollution is defined as the reduction in productivity of soil due to presence of soil pollutants.

  • Pesticides, fertilizers, organic manure, chemicals, radioactive wastes, discarded food and clothes, leather goods, plastic, paper, bottles, tin cans and carcasses contribute towards soil pollution.
  • Industrial wastes contain chemicals like iron, lead, mercury, copper, zinc, cadmium, aluminum, cyanide's, acids, alkalies, etc that reach soil either directly through water or indirectly through air (acid rain).
  • Improper and continuous use of herbicides, fungicides and pesticides to protect crops from pests and fungi alter the basic composition of soils and make it toxic for plant growth.
  • Organic insecticides like DDT, Aldrin, Benzene-hexachloride, etc used against soil borne pests accumulate in the soil due to slow degradation by soil and water bacteria. They result in stunted growth of plants and reduced size of fruit. Their bye-products of degradation reach animals including man through food chain.
  • Radioactive wastes from mining and nuclear processes may reach soil via water or as 'fall-out'. From soil they reach plants and live stock from where they enter human beings through milk and meat. This causes retarded and abnormal growth in human beings.
  • Human and animal excreta used as organic manure to increase crop yield, pollute soil by contaminating soil and vegetable crops with pathogens that may be present in excreta.
  • Intensification of agricultural production by excessive irrigation, excessive fertilizers,  pesticides, insecticides, etc causes soil pollution.
  • Salination in the increase in the concentration of soluble salts in soil
  • It occurs mainly in arid areas due to:
    • Low rainfall
    • Poor drainage and
    • High temperature causing water to evaporate quickly leaving behind salts in high concentration
  • Salination occurs due to:
    • Poor drainage of irrigation and flood waters
    • In summers, salts from deeper strata are drawn up by capillary action and get deposited on the surface. Excess salts form a white crust on the soil surface and adversely affect the water absorbing capacity of the plant.
  • Salinity can be checked by improving drainage and saline lands can be reclaimed by the process of leeching with plenty of freshwater. By this technique, salts at the surface are leachead down to greater depths.
  • Excessive use of canal irrigation disturbs the water balance and creates a problem of water logging due to rise in water table. Water logging causes less oxygen available for respiration of plants.