Monday, September 15, 2014

Natural resources: Water resources

Water resources
Almost 71% of earth's surface is covered by water of which 97% is ocean waterwhich is unusable due to high salt concentration. Almost 2.6% of fresh water is  is trapped in ice caps and glaciers along with some part stored underground. Only 0.4% of the total quantity of water is available in swamps, rivers, lakes and streams.

Surface water sources
Sea water
River and streams
Natural lakes and ponds
Artificial impounding reservoirs

Ground water sources
After glaciers, ice caps and snow fields, ground water is the next largest fresh water reservoir. Precipitation that does not run-off over the surface, percolates through the soil and either accumulates in an underground basin or flows underground in sub surface streams.

Effects of over-utilizing ground water
-Excessive pumping of ground water causes porous formations to collapse resulting in subsidence
-Heavy pumping can lower water table and cause shallow wells to dry-up or even deplete the entire aquifer.
-Over-use of freshwater reservoirs along coast lines often allows salt water to intrude into aquifers rendering the water unfit for domestic, industrial or agricultural purposes.

Ecological pyramids

Ecological Pyramid
Ecological pyramids are of three types:
i. Pyramid of numbers
ii. Pyramid of energy
iii. Pyramid of biomass
The concept of ecological pyramid was developed by Charles Elton; these pyramids are also known as Eltonian pyramids. The pyramids are a graphical representation which depicts the number of organisms, biomass and productivity at each trophic level. All ecological pyramids begin at the bottom with the produces and proceed through different trophic levels. 

Ecological pyramids begin with the producers at the bottom like plants and they proceed to various trophic levels like herbivores consume plants, carnivores prey on herbivores and so on. The highest level is at the top of the food chain.  

Ecological Pyramid

Consider a grassland ecosystem for example:
In a grassland ecosystem, the producer is grass which is small in size but large in number. Hence, it
occupies the lowest trophic level (I trophic level).
The primary consumers are rats (herbivores) and they are more in number than grass. Therefore they
occupy the second trophic level (II trophic level)
The secondary consumers are snakes (carnivores) and they are fewer in number than the rats. They
occupy the third trophic level(III trophic level)
Eagles are the tertiary consumers that feed on snakes and they are at the top of the pyramid with the
least in number. They form the apex in the pyramid of numbers. The diagram is shown above which is self-explanatory.
The pyramid of energy or the energy pyramid describes the overall nature of the ecosystem. During the flow of energy from organism to other, there is considerable loss of energy in the form of heat. The primary producers like the autotrophs there is more amount of energy available. The least energy is available in the tertiary consumers. Thus, shorter food chain has more amount of energy available even at the highest trophic level. 
  • The energy pyramid always upright and vertical. 
  • This pyramid shows the flow of energy at different trophic levels. 
  • It depicts the energy is minimum as the highest trophic level and is maximum at the lowest trophic level. 
  • At each trophic level, there is successive loss of energy in the form of heat and respiration, etc. 
Pyramid of Energy
The pyramid of numbers depicts the relationship in terms of the number of producers, herbivores and the carnivores at their successive trophic levels. There is a decrease in the number of individuals from the lower to the higher trophic levels. The number pyramid varies from ecosystem to ecosystem. There are three of pyramid of numbers:
  • Upright pyramid of number 
  • Partly upright pyramid of number and
  • Inverted pyramid of number.
Upright Pyramid of Number 
This type of pyramid number is found in the aquatic and grassland ecosystem, in these ecosystems there are numerous small autotrophs which support lesser herbivores which in turn support smaller number of carnivores and hence this pyramid is upright.

Pyramid of Number
Partly Upright pyramid of Number 
It is seen in the forest ecosystem where the number of producers are lesser in number and support a greater number of herbivores and which in turn support a fewer number of carnivores.

Partly Upright Pyramid of Number
Inverted Pyramid of Number 
This type of ecological pyramid is seen in parasitic food chain where one primary producer supports numerous parasites which support more hyperparasites.

Inverted Pyramid of Number
The pyramid of biomass is more fundamental, they represent the quantitative relationships of the standing crops. In this pyramid there is a gradual decrease in the biomass from the producers to the higher trophic levels. The biomass here the net organisms collected from each feeding level and are then dried and weighed. This dry weight is the biomass and it represents the amount of energy available in the form of organic matter of the organisms. In this pyramid the net dry weight is plotted to that of the producers, herbivores, carnivores, etc. 

There are two types of pyramid of biomass, they are:
  • Upright pyramid of biomass and 
  • Inverted pyramid of biomass. 
Upright Pyramid of Biomass
This occurs when the larger net biomass of producers support a smaller weight of consumers.
Example: Forest ecosystem.

Biomass Upright Pyramid in Terrestrial Ecosystem

Inverted Pyramid of Biomass
This happens when the smaller weight of producers support consumers of larger weight.
Example: Aquatic ecosystem.

Inverted Pyramid of Biomass in Aquatic Ecosystem

Energy flow in an ecosystem

Energy flow in an ecosystem
The manner in which energy flows in an ecosystem is known as energy flow. It is unidirectional. The
following points are important with regard to understanding energy flow in an ecosystem:
i. Efficiency of producers in absorption and conversion of solar energy.
ii. Using the converted energy (chemical energy – starch) by consumers
iii. Total input of energy as food and its efficiency of assimilation
iv. Energy lost through respiration, heat, excretion, etc at each trophic level
v. Gross production and net production

Two important points to be noted about energy flow in ecosystems are:
i. Energy flow is unidirectional and
ii. There is a progressive decrease of energy as we progress along the food chain. The
energy is lost as heat in metabolic activities such as respiration, hunting, etc.

Structure and Function of an Ecosystem

Structure and function of an ecosystem
The two important aspects of an ecosystem are:
  • Structure and
  • Function

Structure of an ecosystem consists of
  • Composition of biological community (eg: plants, animals and microbes), biomass, life cycles and distribution in space.
  • Quantity, distribution and cycling of non-living materials (macro and micro nutrients, trace elements and water)
  • Variation of conditions like temperature, rainfall, sunlight, relative humidity, wind and topography.
Function of an ecosystem consists of
  • Rate of biological energy flow (production and respiration rates)
  • Rate of nutrient cycles
  • Ecological regulation (Environment regulation in the form of photoperiodism and Organism regulation in the form of nitrogen fixation by organisms)

From the trophic stand-point, an ecosystem has two components
  • Autotrophic component and
  • Heterotrophic component

Autotrophic component involves
  • Fixation of light energy
  • Use of simple inorganic substances like carbon and water
  • Synthesis of hexose sugars (glucose) to complex substances such as polysaccharide carbohydrate (starch), fat and protein synthesis.

Heterotrophic component involves
  • Utilization
  • Rearrangement and Decomposition of complex substances
  • Herbivores, Carnivores and Omnivores (Phagotrophs) and microconsumers (decomposers, osmotrophs and saprotrophs) comprise the heterotrophic component.

Food chains Vs Food webs

GRASS manufactures its food using SUNLIGHT, WATER, NUTRIENTS from soil and CHLOROPHYLL
The GRASS is eaten by a GRASSHOPPER
The GRASSHOPPER is eaten by a FROG
The FROG is eaten by a SNAKE
The SNAKE is eaten by a HAWK.

TREES produce ACORNS which act as food for many MICE and INSECTS.
Because there are many MICE, WEASELS and SNAKES have food.
The insects and the acorns also attract BIRDS, SKUNKS, and OPOSSUMS.
With the SKUNKS, OPPOSUMS, WEASELS and MICE around, HAWKS, FOXES, and OWLS can find food.
They are all connected! Like a spiders web, hence it is called a FOOD WEB.

In a food chain, any disturbance in the food supply affects the entire food chain. However in the food web, any disturbance in the food supply is compensated by other organisms available as food at the same trophic level.

Food webs are far more complex than the simple food chain

Several interconnected food chains form a food web.

The real world we find food webs everywhere. Food chain is only a simplistic view of the complex real world phenomena.

Wednesday, September 10, 2014

Agriculture - Effects of modern methods and options

The widespread use of chemicals in agriculture as fertilizers, pesticides, insecticides and rodenticides without proper technological information have multiplied the hazards to which human beings are exposed. These chemicals spread through the environment and pose a threat to all animals.
Fertilizers are materials that are added to soil to restore and enhance soil fertility to improve the quality and quantity of plant growth.
Fertilizers may be natural or artificial (synthetic). Natural fertilizers are further divided into Organic and inorganic fertilizers. Examples of inorganic fertilizers are Gypsum, Crushed limestone and sulphur rock phosphate while those for organic fertilizers are manure, animal excreta, plant wastes and humus.
Excess fertilizers that are not taken-up by plants, leech into sub-soil water sources and contaminate them. They are non-biodegradable and thus accumulate to reach objectionable levels as they pass through different levels of the food chain.
The main problem with fertilizer use is the contamination of water with nitrates, phosphates and potassium.
Nutrients are lost from agricultural fields through:
-Drainage and
-Attachment to eroded soil particles
Amount of nutrient lost depends on:
-Soil type and organic matter content
-Depth to groundwater and
-Amount and type of fertilizer and irrigation used
The major nutrients in fertilizers are:
-Nitrogen (N)
-Phosphorus (P) and
-Potassium (K)
Nitrogen is readily lost due to high solubility in nitrate form. Leaching of nitrate from agricultural fields can increase groundwater concentrations to unacceptable levels for drinking water supply
High nitrate levels in drinking water are dangerous to human health
Phosphorus cannot be washed out of soil but can be washed into surface waters together with the soil that is being eroded.
Phosphorus is not dangerous. However, it stimulates the excess growth of algae and this process is called "eutrophication". The algae eventually die and decompose resulting in depletion of dissolved oxygen thereby killing fish.
Potassium does not cause water quality problems. Its solubility is similar to phosphorus i.e., it is similarly bound by soil particles and can be by erosion.
Qualities of an ideal pesticide:
-It should only kill target pest
-Have no short term or long term effects on non-target organisms
-Should be able to be broken down into harmless compounds in a short time
-Should prevent the development of genetic resistance in target organism
-Save money compared to making no effort to control pest
Since 1945, different types of synthetic organic chemicals have been used as pesticides.
Worldwide, 2.3 million Tonnes of pesticides are used (85% in developing countries.
Synthetic nsecticides are of the following types:
Chlorinated hydrocarbons

DDT and other slowly degradable chlorinated hydrocarbon insecticides were banned in mid 1970s
Organophosphates are more rapidly biodegradable but are water soluble and could possibly contaminate surface and groundwater sources.
Chlorinated hydrocarbons are fat soluble
Farmers apply non-persistent pesticides at regular intervals to ensure effective insect control. The regular use of using non-persistent pesticides is almost as good as using persistent pesticides.
Pyrethrin (from wild chrysanthemum type plants) and Rotenoids (from roots of rain forest legumes) are produced from wild plants and can be effectively used as biological control agents as they are:
-Effective in low doses and
-Cause little harm to mammals
The following are the benefits of using pesticides:
-pesticides save lives
-they increase food supplies and lower food costs
-they increase profits of farmers
-they work faster and better than alternatives
-safer and more effective products are continuously being developed.
Development of genetic resistance
Modifying cultivation process
-crop rotation
-planting rows of hedges or trees in and around crop fields
-adjusting planting times
-destroy diseased or infected plants
-growing crops in areas where their major pests do not exist
-using plant diversity to control pests by adopting:
                         agro-forestry and
-artificial selection, cross breeding and genetic engineering varieties of plants and animals that are genetically resistant to certain pest insets, fungi and diseases.
-biological pest control against various natural parasites and pathogens can be introduced to control the populations of specific pests.
Organic agriculture is defined as an ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity. It is based on minimal use of off-farm inputs and on management practices that restore, maintain and enhance ecological harmony.

Agriculture has been a practice in use for hundreds of years. It provides countless people with sustenance and livelihood all over the world. However, modern practices in agriculture have led to several damaging effects on the environment listed below:
1.Agriculture increases carbon dioxide levels making it one of the main sources of carbon dioxide emissions for decades. This in-turn aggravates the problem of global warming and consequent sea level rise.
2.Animal waste from farms contains harmful pathogens known to cause disease and infection. By getting into soil and water systems they create irreversible damage to land and pose health risks towards humans. These problems lead both directly and indirectly to these health risks, and may causes disorders such as hepatitis and meningitis.
3.Fertilizers also put forth several complications. They contain harmful elements such as nitrogen and phosphates, both of which negatively affect air and water quality. Its use causes the release of ammonia, nitrogen runoff and eutrophication, all of which have negative effects on the environment.
4.Impacts also include increased water or wind erosion, depleted groundwater supplies in irrigated areas,
5.Modern agriculture converts an ever-increasing portion of the earth's land surface to monoculture. As a result, the genetic and ecological diversity of the planet erodes. The conversion of diverse natural ecosystems to new agricultural lands and the narrowing of the genetic diversity of crops contribute to this erosion.
6.In addition to adding pollutants to water, soil and air, modern agriculture practices can cause soil disturbance by using heavy machines and tilling equipment. This, in turn, creates soil erosion and degrades the quality of surrounding farmland.
7.A number of "ecological diseases" have been associated with the intensification of food production. They may be grouped into two categories: diseases of the ecotope, which include erosion, loss of soil fertility, depletion of nutrient reserves, salinization and alkalinization, pollution of water systems, loss of fertile croplands to urban development, and diseases of the biocoenosis, which include loss of crop, wild plant, and animal genetic resources, elimination of natural enemies, pest resurgence and genetic resistance to pesticides, chemical contamination, and destruction of natural control mechanisms.

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.