Damages caused to environment, biotic or abiotic by developmental activity and the cost incurred for the adoptation of control measures depend largely on the nature and the magnitude of the activity undertaken.
All developmental activities are not equally injurious to the environment. Environmental damages caused by a developmental activity can be grouped into following categories:
Construction activities, such as building of dams large water reservoirs, highways and railway track etc. usually cause significant adverse effects or at times enormous damages to human settlements, natural habitats and wild life.
For example, construction of a water reservoir or a dam may cause a large area of land to be flooded with water. Everything that occurs in the area is usually destroyed be it a village or a township or agricultural land or a forest. Mitigative measures taken in such cases involve displacement of human settlements to other places, animal life migrates on its own while plants have to suffer as they cannot move away.
There may be changes in underground water table. Little adjustments may take place in the under-ground rock strata due to the pressure exerted by standing water table. Once adequate mitigative steps are taken and the initial adjustments are made the locality is transformed into a lake and everything settles down. There is little impact during the following periods. There is no need of a regular impact monitoring and mitigative measures in times to come.
(2) Developmental Activities Causing Recurrent Damages for Which Mitigative Measures have to Regularly Taken as Long as the Activity Continues :
A number of industries on the other hand cause adverse environmental impacts as long as they remain in operation. These industries are those industries which use some raw material and produce a finished product along with plenty of solid, liquid or gaseous wastes. The damage caused to the environment depends upon the magnitude of waste materials produced per unit time. It is these industries which have to be closely watched and the wastes discharged have to be appropriately treated before disposal. The mitigative efforts have to be undertaken as long as the industry remains functional.
The relationship between the cost of damages and the control cost shows a definite pattern in such cases. As the control measures are undertaken there is rather a significant reduction in the magnitude of damages caused. However, a point is reached beyond which the raised levels of mitigative measures or in other words more expenditure are not so effective.
For example, after having eliminated nearly 75% of pollution it cost much more to reduce an additional 5% – to remove the pollution load by another 5% much larger efforts are needed which become even more costly and to remove the pollution completely becomes a herculean task.
Usually, it is at the point where maximum Environmental Impact reduction in the load of pollution is achieved with minimum expenditure that mitigative efforts are maintained. Thus, a fraction of pollution which causes adverse environmental effects is usually left for the nature to take care of as mitigative efforts can do little about it.
The effect of pollution caused by developmental activity usually disappears soon after the activity is terminated. However, there are some industries which leave more or less a long lasting impact on the locality. In this category come nuclear power plants, establishments using radioactive materials and a number of mining and processing industries. The waste materials disposed of by these industries is of toxic nature which persists in the system for long durations of time.
Coal fired power plants produce large quantities of fly ash which has a significant quantity of heavy metal oxides and toxic trace elements which continue to harm the biotic constituents of the system for years to come. Clark Fork Basin, Montana, U.S.A., which has been a site of more or less a century of mining and smelting activity, has introduced so much of toxic heavy metals in the system that the locality has become virtually a dead zone.
Pangua copper mine at Bougainville, New Guinea has disposed off so much of heavy metal contaminated tailings in the Kawarang Jeba river system that no aquatic life can survive in the waters. In Japan, 6,700 hectares of rich crop land has become too much contaminated with heavy metals and toxic trace elements.
In U.K., about 400,000 hectares has been lost completely to smelters since Roman times. The land has become a bare dead zone of little agricultural use. Nuclear power plants similarly contaminate the locality with radioactive wastes which may have very long half lives. For thousands of years to come the locality becomes contaminated with radio-active materials and hence of little use to the mankind.