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close this bookUnited Nations University - Work in Progress Newsletter - Volume 12, Number 1, 1989 (UNU, 1989, 12 pages)
View the document(introductory text...)
View the documentSustaining the Earth
View the documentAnticipating global trends: Aspects of UNU work for the period 1990-1995
View the document'An uncontrolled global experiment...'
View the document'A little breathing space': Report from the Budapest
View the documentEnergy savings: Sooner much better than later
View the document'The rich get richer...'
View the documentOld wine in new bottles?
View the documentTectonics of the desert cities
View the documentMan in the mangroves
View the documentDiverting the Nile
View the documentLosing the soils of Africa
View the documentIn fairness to the future

Tectonics of the desert cities

By R.U. Cooke, D. Brunsden, J.C. Doornkamp and D.K.C. Jones

Tectonics is a branch of geology concerned with the massive shiftings and crunchings of the Earth's crust that have molded the face of the planet over the millennia. Today, observers of environmental change speak of the "tectonics of population" - the vast shifting of peoples away from the rural areas of the world into the unworkable crunch of teeming metropolitan areas.

Population is a basic driving force in human-caused environmental change. Cities, for example, are hotter, wetter, less windy, and more stormy: their clusterings of population create their own weather conditions. One of the more environmentally worrisome urban problems is in the world's drylands. The globe's urban dryland inhabitants live in cities as varied in cultural needs and impulses as Dakar, Senegal; San Bernardino, California, USA; Cairo, Egypt; Volgograd, USSR; Damascus, Syria; Riyadh, Saudi Arabia; Delhi, India; Ulan Bator, Mongolia; and Beijing, China. But virtually all of these cities are growing at an alarming rate. The following discussion of the urban drylands is excerpted from the book, Urban Geomorphology in Drylands, by R.U. Cooke, D. Brunsden, J.C. Doornkamp and D.K.C. Jones, based on UNU research on dryland problems, and published jointly by UNU and Oxford University Press. - Editor

The world's drylands include 355 cities of over 100,000 inhabitants, together with a large number of smaller urban settlements. In recent years, and for a variety of reasons, the population of many of these urban areas has been growing rapidly, at rates of up to 16 per cent a year. Such rapid growth has pushed urban limits into new territory - agricultural or pastoral lands or, commonly, virgin deserts. The voracious dryland towns and cities have consumed and are continuing to consume huge tracts of land.

The available data suggests that, in Africa, 21.7 million people live in dryland cities with 100,000 or more inhabitants. There are 48.6 millions in the drylands of North and South America, and 93.7 millions in Asia. It has been estimated that the total population of drylands in the world as a whole is 628.4 million - or 14 per cent of the world total. It would thus seem that more than a quarter - 26.1 per cent - of all the world's dryland inhabitants live in urban agglomerations with populations of 100,000 or more.

Within the drylands, it is evident that urban growth and urbanization are proceeding in a wide variety of cultural, social, economic and political contexts. From the point of view of environmental management, a range of types of urban development can be recognized. At one extreme, there is usually planned, technologically advanced urban development in societies such as those of the USA, the USSR, Israel, South Africa and Australia. At the other extreme, there is development in more poorly equipped societies, such as those in the Sudan, Algeria, Peru, India and Pakistan. Between these extremes there is, for example, technologically advanced urban development in rapidly changing oil-based societies that have recently chosen to invest in urban growth; such countries as Kuwait, Saudi Arabia, Iran and Iraq fall into this category.

Problems arising from urban development to some extent vary within these different contexts, but most dryland cities are united in their numerous common physical environmental problems and their need for planning controls and engineering expertise to help overcome them. If anything, the problems are most serious in those communities where growth is uncontrolled, and planning is primitive or absent; and it is in such areas that the rate of growth of urban populations is often so strikingly rapid.

The rapid growth of urban populations in less-developed countries may be regarded as the outcome of both rapid rates of rural-to-urban migration, and natural population increase. The combination of 'pre-industrial' fertility levels with 'post-industrial' mortality rates means that Third World cities are experiencing some of the highest rates of natural increase ever found in cities.

At the same time, rural-urban migration is accelerating due mainly to the attraction of high urban wages and the collapse of traditional economies - the result is a tide of in-migration.

In Caracas, Venezuela, for example, it has been estimated that from 1960 to 1966 migrants comprised 50 per cent of the total population increase. Similarly, MacGregor and Valverde's 1975 study of Mexican cities showed that in Monterey 31.3 per cent of the population are in-migrants, and the figure is 48 per cent for Tijuana, 34 per cent for Mexicali, and 32.9 per cent for Nuevo Laredo. In addition, burgeoning urban populations in Third World dryland cities may lead to a dramatic increase in local water consumption and despoliation of agricultural land around cities, which, in turn, may generate further waves of rural migrants and yet more demands for water.

Urbanization without Jobs

These forces have resulted in a situation in many Third World cities where urbanization is in advance of industrialization and employment provision - thereby replacing rural underemployment by urban unemployment, and the growing 'ruralization' of towns. The most obvious tangible outcome has been the spontaneous explosion of squatter settlements in many Third World cities - the extent of which is suggested by the table on this page.

Such settlements pose a multitude of problems for the urban community. Some of the physical environmental problems of such urban areas might be avoided or alleviated if methods used in planned, technologically advanced urban development in rapidly growing 'western' societies could be sensibly applied to them. The techniques and approaches available through geomorphology are among those that may be of value.

Different Cultural Contexts: Two Extremes

Rapid urban growth in drylands has occurred in varied cultural contexts and, as a result, attitudes toward the phenomenon are quite diverse. At one extreme, planned controlled development is considered essential in order to prevent environmental and social abuse, to husband resources, to control expenditures, and to ensure the creation of urban areas that are attractive and acceptable to a majority of their inhabitants. The USSR and the USA exemplify this view.

At the other extreme, cities have grown in some dryland societies very rapidly by a process of almost spontaneous and uncontrolled expansion that has been generated largely by population growth and increasing employment opportunities. Such growth often reflects either a laissez-faire attitude or, more commonly, an inability - for political, economic, or other reasons - to control development. At its worst, uncontrolled growth gives rise to squatter settlements or shanty towns, as in many poorer Third World countries, and it commonly creates serious social and environmental problems.

Environmental Data: Key to Planning

It is our view that planning - and in particular the use of environmental information in the planning process - can contribute fundamentally towards preventing some of the undesirable consequences of uncontrolled development. The experience in the use of environmental information in the planning process of dryland cities where development has been controlled can be instructive to those responsible for the management of urban affairs in dryland cities that are at present without such control.

Spreading Desert Slums



City population (thousands)

Uncontrolled settlement

Total population (thousand)

As percentage of city population

Dakar, Senegal





Baghdad, Iraq





Karachi, Pakistan





Ankara, Turkey





Santiago, Chile





Lima, Peru





Caracas, Venezuela





Maracaibo, Venezuela





Source: UN General Assembly (1970).

For environmental information to be useful and effective, however, it is essential that it be presented at a particular time in the planning process. Each planning phase - whether at the national, regional or individual city level - characteristically includes a number of stages which, while they are generally sequential, are distinguished by continuous consultation, feedback and overlap. Procedures vary locally, and in particular the extent of public involvement varies greatly between communities. Environmental information may be relevant at all stages.

In addition, the phases in the planning process are usually associated with particular agencies of public and private administration in a generally hierarchical manner. Thus, for example, national agencies are generally responsible for national planning, and municipal authorities generally control land-use and site planning. But the actual implementation of plans might be the responsibility of any agency in the hierarchy. For example, a factory might be developed by a national agency (e.g. a Department of Public Works) or by a local building contractor. In this generally hierarchical structure, there should be a continuous two-way flow of information. Higher-order agency planning will usually be a constraint on lower-order planning; at the same time, higher-order agencies may well find themselves involved in lower-order decision-making and their activities restricted by lower-order planning regulations.

Finally, implementation of city-level plans is normally accomplished through local guidelines and legal controls. The city plan itself normally embodies community goals and a set of development guidelines. Detailed guidelines on land-use areas, and on intensity of use and general requirements within designated areas may be achieved through zoning ordinances (as in the USA, for example) or their equivalent. Such ordinances may also phase development (to ensure appropriate prior provision of services, for example) or provide for sequential land-use (to optimize, for instance, the use of resources). Subdivision ordinances (or their equivalent) control the detailed design layout of a development area within a zone designated for a particular use. Site-development ordinances can control the way in which a site is engineered, and often incorporate requirements for slope development and environmental hazard avoidance. Building and related codes control the nature of construction.

Environmental Information: Sooner the Better

Environmental information is generally thought of as primarily of interest to the planner who ultimately control development, and to the engineer, who is actually responsible for it. But it may also be of value to the developer, and to public interest groups. In general, the sooner the planner or other interested party is aware of, and appropriately informed about potential natural hazards and resources, the better he is able to anticipate areas of possible land-use conflict, to develop planning priorities, and recognize possible problems and solutions. Thus environmental information may be required from the beginning of the planning process.