1. A determination of the initial reference state;
2. An estimate of the future state 'without action'; 
3. An estimate of the future state 'with action'. 

(a) Establishment of the Initial Reference State 

Assessment of environmental change pre-supposes knowledge about the present t state. It will be necessary, therefore, to select attributes that may be used to estimate this state. Some of these will be directly measurable; others will only be capable of being recorded within a series of defined categories, or ranked in ascending or descending order of approximate magnitude. At worst, it will be necessary to record the state of the environment by the presence or absence of some of the attributes. Difficult decisions will need to be made about the population (in a statistical sense) which is to be represented by the measured variables, and the I extent to which sub-division of this population into geographical regions, ecosystems, etc., is either feasible or necessary. In fact, it must be emphasized that the establishment of an initial reference state is difficult; not only are environmental systems dynamic but they contain cyclical and random components. An initial state cannot therefore be described satisfactorily with a once-off survey; even with a regular monitoring programme, a description of an existing environmental state still contains a degree of subjectivity and uncertainty. The data problems are discussed further in Appendix 1.

(b) Predicting the Future State in the Absence of Action

In order to provide a fair basis for examining human impacts, future environmental states in the absence of action must be estimated. (See Section 1.5 and Figure 1.1.) As an example, the populations of a species of animal or fish may already be declining, due to over-grazing or over-fishing, even before a smelter is built. 

This part of the analysis is largely a scientific problem, requiring skills drawn from many disciplines. The prediction will often be uncertain, but the degree of uncertainty should be indicated in qualitative terms at least. For example, forecasting of droughts two or three years in advance is not yet possible, although the statistical probability that a drought (of a given severity) will occur sometime in the next hundred years can be estimated with some confidence. 

Predictions of the behaviour of biological sub-systems and their responses to environmental stresses are also subject to uncertainty. Fortunately, there are mathematical techniques for describing these uncertainties and subjecting them to critical analysis. The decision-maker should be aware of the degree of uncertainty which surrounds the predicted state of the environment and have some understanding of the methods by which this uncertainty is calculated. 

(c) Predicting the Future State in the Presence of Action 

For each of the proposed actions, and for admissible combinations of these actions, there will be an expected state of the environment which is to be compared with the expected state in the absence of action. Consequently, predictions similar to those outlined in the sub-section above must be derived for each of the proposed alternatives. 

Forecasts will be required for several time-scales, both for the 'with' and the 'without' action cases. 

3.4 AREAS OF HUMAN CONCERN 

We assume that the welfare of human beings, interpreting welfare in the broadest sense, is the main preoccupation of environmental planning. If this is so, the wisdom of a decision-maker must be judged in relation to areas of human concern. 

An attempt is made in Table 3.3 to list the main classes of human concern which are likely to be affected by 'action' proposals. The ordering is no measure of relative importance, which will vary from place to place and from time to time. There is some overlap and many interactions between classes. For example, health (Class 6) depends in part on economic and occupational status (Class 1 ). 

It has not been considered useful or appropriate to present exhaustive sub-sets of concerns that fall within each class but only to give a few indicative examples. We recommend, however, that each jurisdiction prepare a list of relevant categories. In some instances there is merit in doing this for each proposed action.

Table 3.3 Areas of Human Concern (Impact Categories)

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1.	Economic and occupational status	Displacement of population; relocation of population in response to employment opportunities; services and distribution patterns; property values
2.	Social pattern or life style	Resettlement; rural depopulation; change in population density; food; housing; material goods; nomadic; settled; pastoral agricultural; rural; urban
3.	Social amenities and relationships	Family life styles; schools; transportation; community feelings; participation vs alienation; local and national pride vs. regret; stability; disruptions; language; hospitals; clubs; recreation; neighbourliness
4.	Psychological features	Involvement; expectations; stress; frustrations; commitment; challenges; work satisfaction; national or community pride; freedom of choice; stability and continuity; self-expression; company or solitude; mobility
5.	Physical amenities (intellectual, cultural, aesthetic, and sensual)	National parks; wildlife; art galleries and museums; concert halls; historic and archaeological monuments; beauty of landscape; wilderness; quiet; clean air and water
6.	Health	Changes in health; medical services; medical standards
7.	Personal security	Freedom from molestation; freedom from natural disasters
8.	Religion and traditional belief	Symbols taboos; values
9.	Technology	Security; hazards; safety measures; benefits; emission of wastes; congestion; density
10.	Cultural	Leisure, fashion and clothing changes; new values; heritage; traditional and religious rites
11.	Political	Authority ; level and degree of involvement; priorities; structure of decision-making; responsibility and responsiveness; resource allocation; local and minority interests; defence needs; contributing or limiting factors; tolerances
12.	Legal	Restructuring of administrative management; changes in taxes; public policy
13.	Aesthetic	Visual physical changes; moral conduct; sentimental values
14.	Statutory laws and acts	Air and water quality standards; safety standards; national building acts; noise abatement by-laws

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3.5 IMPACT INDICATORS 

An impact indicator is an element or parameter that provides a measure (in at least some qualitative sense ) of the significance of the effect, i.e., of the magnitude of an environmental impact. Some indicators such as morbidity and mortality statistics and crop yields have associated numerical scales. Other impact indicators can only be ranked on simple scales such as 'good-better-best' or 'acceptable- unacceptable'. 

The selection of a set of indicators is often a crucial step in the impact assessment process, requiring an input from the decision-maker. In the absence of relevant goals or policies, the assessor himself may suggest some indicators and scales, but he should not proceed with the assessment until his proposals are accepted. 

The most widely used impact indicators are those within Class 14 of Table 3.3, i.e., indicators such as air and water quality standards that have statutory authority. For example, the problem of designing an environmentally acceptable oil-fired generating station is simplified for the engineer if he is given one or both of:

1. emission standards for various pollutants; 
2. air and water quality standards. 

These standards integrate in some sense the worth that a jurisdiction places on clean air and clear water. The numerical values have been derived from examination of the available toxicological data relating pollutant dosages to health and vegetation effects, combined with a consideration of best practical technology. Admittedly the evidence is sometimes incomplete and controversial, but the assessor should accept the derived standards. The impact assessment process is not the appropriate forum for debates on the validity of numerical values. A possible exception occurs when, in the absence of national standards, a local decision-maker or an overseas engineering firm decides to employ standards 'borrowed' from another jurisdiction. Toxicological evidence based on temperate-zone studies cannot always be confidently extrapolated to the tropics or to the arctic. 

Although the 'standards' mentioned above are useful impact indicators, they do not reflect the totality of human concerns. Other factors such as the displacement of arable land by industry are equally important. An EIA that ignores these other components is incomplete and sometimes misleading. 

After the impact indicators and their scales are selected, their values must be estimated from the predicted values of the environtmental effects for each project alternative and for several time-scales. 

3.6 ESTIMATION OF THE TOTAL ENVIRONMENTAL IMPACT 

In some defined way, the description of the environment must be collapsed to the behaviour of a few variables, which must then be related to the impact indicators. An objective, although not always achievable, is that for each of the proposed actions and for each of the human concerns, the expected outcomes can be compared on numerical scales.

The original measurement units for the impact indicators will normally be quite different: some may be numerical, while others are in the form of a series of classes. At this point in the analysis, therefore, the assessor might wish to convert the scale into a comparable set using some system of normalization. In the most primitive system, each indicator is rated as being significant-positive, insignificant, or significant-negative; the numbers of positive and of negative counts are then compared. Because some human concerns are frequently more important than others, however, a series of weights may be assigned to the concerns. For example, one may make a value judgement that recreational land use is more important than forestry. 

3.7 RECOMMENDATIONS OF THE ASSESSOR 

Having estimated the environmental impacts of the proposed action, the assessor may make recommendations. The wisdom of these recommendations depends greatly on the extent to which there is discussion spanning many disciplines among the assessor's staff and advisors. This group of people should include scientists, sociologists, and economists, each of whom feels a personal commitment and sense of excitement. An individual who is 'assigned' unwillingly to a project is likely to be counter-productive. 

We should not overlook the contributions that can be made by economists in estimating trade-offs. Consider, for example, the question of conflicting land uses. Often the best location for new industry is to be found on a river or coastline because of the need for water or port facilities. Suppose, however, that the site is also best for agriculture, urbanization, or recreation. There is then a requirement for an economic comparison of alternative plans that are sub-optimal for some components but optimal for the whole. This is not to suggest, of course, that the decision will be made on economic grounds alone. The preservation of a bird sanctuary may be of overriding importance, for example. 

3.8 THE LEVEL OF DETAIL IN AN EIA 

The level of detail in an EIA depends on: 

1. the sensitivity of the local environment; 
2. the scale of the proposed development, and its potential effects; 
3. the social value placed nationally and/or locally on preserving or enhancing environmental quality; 
4. the resources and scientific expertise of the country; 
5. the time available for assessment. 

In some jurisdictions, the assessor prepares a preliminary EIA, which forms the basis for deciding whether a major EIA will be necessary. 

There are maximum, as well as minimum efforts that can be directed usefully towards the preparation of EIAs. These 'outer limits' are not well defined, but vary with the class of project and with the country concerned. A useful step for a jurisdiction to take would be to provide guidelines on the contents and lengths of EIAs for various classes of projects. These guidelines would vary from country to country , and cannot be specified here. 

3.9 THE GENERAL APPLICABILITY OF EIAs 

EIAs have been most widely used in the industrialized countries, but they have general applicability, provided that they take account not only of the physical and biological characteristics of a particular region but also of the local socio economic priorities and cultural traditions. Countries, and often different provinces within a country , are at different stages of economic development, and have different priorities, policies, and preoccupations. The probably adverse consequences of any development must be weighed against estimated socio economic benefits. What is unacceptable will vary greatly from one country or situation to another. 

In developing countries particularly, the process of elaborating EIAs must in no way be viewed as a brake or obstacle to economic development, but rather as a means for assisting in planning the rational use of the country's natural resources. This is because the economic development and prosperity of whole nations are tied to the successful long-term management of natural resources. The cost of an EIA will usually be much less that of remedial measures that may subsequently be necessary. 

Although relatively simple EIAs may be all that is possible in some jurisdictions, due to a Jack of local expertise, such assessments are valuable first steps and should be encouraged. In this connection, we recommend to international agencies that provide aid and technical assistance to developing countries: 

1. that an impact assessment be required in the case of each major development project that the international agency in tends to support; 
2. that support be given to activities designed to strengthen local capabilities in preparing EIAs; 
3. that in particular, help be given to assist in the development and testing of procedures to identify sensitive environments (a land classification would be useful, even if crude) and to identify potentially disturbing developments; guidelines outlining the kinds of activities that might cause environmental disruption would be useful. 

Apart from any consideration of possible adverse effects on the quality of life, the environmental effects on many development projects may well be crucial for their economic viability. Examples of failures in this respect are the West African groundnut scheme of the late 1940s and the Kariba dam project in Rhodesia.

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The electronic version of this publication has been prepared at the M S Swaminathan Research Foundation, Chennai, India.