As far possible, prediction scientifically characterizes the
impact's causes and effects, and its secondary and synergistic consequences for
the environment and the local community. Prediction follows an
activity-component relationship (e.g., discharge of liquid effluent as an
activity and river water quality as an environmental component) and estimates
the subsequent effects (e.g., such as reduced concentration of dissolved oxygen,
reduced fisheries). Prediction draws on physical, biological, socio-economic,
and anthropological data and techniques. In quantifying impacts, it may employ
mathematical models, photomontages, physical models, sociocultural models,
economic models, experiments, or expert judgements.
To prevent unnecessary expense, the sophistication of the
prediction methods used should be kept in proportion to the "scope'' of the EIA.
For instance, a detailed mathematical model of atmospheric dispersion should not
be used if only a small amount of relatively harmless pollutant is emitted.
Simpler models are available and are sufficient for the purpose. Also, it is
unnecessary to undertake expensive analysis if they are not required by the
decision makers for whom the EIA is being done.
All prediction techniques, by their nature, involve some degree of
uncertainty. So, along with each attempt to quantify an impact, the study team
should also quantify the prediction's uncertainty in terms of probabilities of
"margins of error''.
A shortcoming of many detailed EIAs is that social and cultural
impacts are not given the prominence they deserve in describing the extent of
changes expected to result from a major development project. This has probably
been due to the bias of physical and biological scientists against the
comparatively younger disciplines of cultural anthropology and sociology. This
is an unfortunate bias, since sociocultural impacts are the ones that would
affect the local community in their everyday lives. A consideration of
sociocultural impacts should be integrated, wherever possible, into every
discussion of physical/biological change, and not just treated separately in a
minor chapter or appendix. Several methods and analytical tools are available
for this purpose; they are discussed in detail in Chapters 4 and