In a natural ecosystem everything is related to everything else. Any change in any of its components, biotic or abiotic, may bring about a series of small or larger changes. Smaller changes are absorbed by the system or are tolerated while the larger ones may leave a permanent scar.
The magnitudes of changes caused by man are often enormous. Human activity, which is characterised by over-exploitation of resources and pollution of the environment, usually in reduction of biodiversity- at times even to the extent of total disappearance of life from the system.
With rapid expansion of human influence increasing larger areas with natural habitats are being subjected to such destruction and it has become necessary to stop it. If we cannot stop it altogether at least we can slow down the pace of the degeneration of wild life and the environment. Human activity which causes adverse impacts on large scale must be subjected to a close scrutiny, before being undertaken, for the environmental damage it would cause and proper mitigative steps should be taken to repair the damage.
Although, even seemingly harmless activities, like agriculture, residential establishments, villages, townships etc. may cause some adverse effect on wild life and natural systems, their impact is rarely monitored. Important human activities which cause environmental damages on a large scale are usually subject to Environmental Impact Assessment. These activities are:
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1. Construction Activities.
2. Manufacturing Industries.
3. Mining Projects.
4. Power Generation Projects.
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Large construction projects such as big dams, water reservoirs, highways, airports, harbours etc. require environmental impact assessment as they disturb the natural habitat and environment on large scale. Mega-dams are particularly important in this connection. They are built by blocking natural water-ways in river-valleys – the sides of valley form a natural wall while the dam is built across the course of the river.
Large areas of land within the valley are submerged which effect human establishment’s agricultural fields, wild life habitats, natural forests, architectural monuments etc. The pressure exerted by standing water table may destabilize the underground rock formations. Underground water table of the locality nearby is raised. The bottom of the reservoir is gradually filled up by silt and sediments deposited by the stagnant water which makes it shall lower as time passes.
Thus, enormous ecological hydrological, geological and socio-economic impacts are produced by construction of a mega-dam. The reservoir of water represents a huge water-bomb perched at the top for the people living downstream. Any accident or sabotage could wipe out everything which comes in the way of rapidly gushing waters of the breached dam. The water in these days is chiefly used for agriculture and power generation which in-fact benefits people of other localities much more than those actually affected by construction activity i.e., the people living in the valley.
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Construction of highways across biologically significant localities is injurious to wild life and habitats. Smoke and fumes discharged by passing vehicles pollute the locality. Traffic activities scare away the animals and produce an impact almost equivalent to habitat fragmentation. The overall species diversity declines. Construction of air-ports requires large tract of land to be cleared of natural vegetaion.
Forests are replaced by grasses and weedy plants. While flights and other activities scar away the wild life the locality has to be cleared of all birds. As a precaution against ‘bird strikes’ – collision of planes with birds could jam the propellers of the plane or air intake nozzles of jet liners resulting in serious accidents.
Marbours with frequent passage of ships disturb the shore line on either side while oils, greeses and other wastes discharged from the ships causes pollution of coastal areas. This results in disappearance of animal life while plant species are replaced by one or few pollution tolerant weedy species which may create another problem.
(2) Manufacturing Industries :
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For a large number of industrial units environmental impact assessment is essential as they are often responsible for causing environmental distress on large scale. The most important aspects of the impact of manufacturing industries on the environment is the pollution caused by industrial effluents such as waste waters, solids and gases produced in majority of industries.
The amount of these discharges depends on the magnitude of production which multiplies when a number of industries are concentrated in what is commonly referred to as Industrial State or area. Industries using coal as a source of power create plenty of smoke waste gases and fly-ash. Transport activity and labour settlements associated with the industries cause another set of problems.
(3) Mining and Processing Industries :
Mining is a dirty industry. Each step in mining and processing operation produces large quantities of waste material. Most of the mines of today are simply surface excavations and the first task of a miner is to remove whatever lies over the mineral deposits. This material called ‘Over-burden’ in miner’s language causes dust storms, cloggs streets and water ways and has to disposed off.
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Though under-ground mining with a system of shafts and tunnels does not produce as much wastes as open cast mining does, the useless material excavated is usually enough to cause environmental troubles. Almost similar problems arise from the disposal of waste materials after concentration of the ore. This material, called tailings in miner’s language is rich in metal content and could cause toxicity to plants and animal life if discarded in an aquatic system. If left as such on land harmful toxic metal rich leachates are produced.
The processing of ore involves procedures which result in production of large quantities of sulphur dioxide, carbon monoxide and carbon dioxide along with large quantities of smoke shoot and flyash which pollute the atmosphere and have been considered an important source of Acid rains.
Environmental Impact Assessment is therefore essential for most of the mining and processing industries. The magnitude of these emissions is dependent upon the grade of ore or the percentage of useful constituent and the quantity of production in the industries concerned. These factors should also be taken into consideration while conducting environmental impact assessment for mining and processing industries.
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The demand of electric power of a modern society is enormous. Domestic uses of electricity constitute an insignificant amount as compared to the requirements of manufacturing industries and mining and processing plants. Though, there are other sources of energy, such as hydroelectric, nuclear or solar power, the mankind largely depends on fossil flues for power generation. Nearly half of the total coal produced worldwide is burnt in our power plants to produce electricity.
Naturally, a huge quantity of smoke waste gases shoot and fly-ash is produced by our power generation units which contaminate all the components of our environment. High nitrogen and sulphur content of coal is responsible for production of large quantities of oxides of sulphur and nitrogen while carbon monoxide and carbon dioxide cause another set of problems.
Large amounts of heated waters are usually discharged from a power plant which create problems in water bodies where they are released. A thorough scrutiny of power plants and an exhaustive Environment Impact Assessment is, therefore, necessary for each power generating units which we setup.