2.6. The discussion that follows attempts to identify and describe some of the environmental side effects that have been known to accompany, in varying degrees, the process of development in agriculture, industry, transport and human settlement. These side effects take several forms and may be grouped into a number of categories. These are:

1. Resource deterioration: the deterioration, for example, of mineral, soil or forest resources;

2. Biological pollution: the pollution represented by agents of human disease, and by animal and plant pests;

3. Chemical pollution: arising out of air pollutants, industrial effluents, pesticides, metals, and detergent components and similar agents;

4. Physical disruption: as reflected, for example, by thermal pollution, silting and noise; and

5. Social disruption: of which congestion and loss of a sense of community are

These side effects manifest themselves in varying degrees depending on the sectors concerned, the particular geographical regions involved, and the stages of development attained by different countries. The first two categories are commonly experienced by most developing countries as are also silting and perhaps social disruption, whilst urban air pollution is becoming a problem of increasing importance in the larger cities of certain developing countries.

2.7. Although these side effects are likely to manifest themselves in the process of development, they need to be assessed within a framework which helps to establish their relative importance. A basic consideration would be the way in which a development activity relates to the carrying capacity of a country's natural, and even social, system. Such issues as the speed at which environmental degeneration is taking place, the degree of its severity, the area that it covers, whether the environmental impact is reversible or irreversible, and at what cost and over what period of time are all of relevance in this connexion. The scale and pattern of a country's production and consumption structure are also of relevance in assessing the impact of environmental side effects. The use and disposal of materials and their environmental implications are, for exemple, influenced by the level of technology since this is relevant to the nature of inputs and outputs in the production process. Similarly, consumption patterns are of importance. In societies where the levels of non-discretionary expenditure -- i.e. expenditures on basic necessities -- are high, the process of consumption exerts adverse environmental effects of a lower order of magnitude. On the other hand, higher levels of discretionary consumption, particularly of more sophisticated manufacturing goods, generally produce a greater environmental impact. The social structure of a society, and its pattern of income and wealth distribution, are thus factors which are also of relevance.

2.8. Within a framework appropriate to its situation, a country may ascertain the nature of its environmental problems, and examine alternative forms of action in dealing with environmental policies. Environmental side effects which are encountered in the development of various sectors should receive selective treatment. They should first be evaluated in terms of the development priorities which guide the planning considerations of any country. Those side effects which directly frustrate the development objective should be given the most immediate attention for remedial action. Those of peripheral concern will inevitably receive less emphasis.


2.9. The process of agricultural development often involves the transformation of low productivity systems of agriculture into systems where productivity is relatively high. In the course of this transformation, cultivation practices on existing lands are improved, the infrastructure of facilities and services for agricultural production is expanded, and new lands brought under cultivation through extensive systems of irrigation and river basin development.