Urbanisation (US spelling: 'urbanization') is a word with two different meanings. According to the United States Postal Service, an 'Urbanization' is an 'area, sector or development within a geographic area'¹. Urbanizations, abbreviated URB, are an essential part of the address format for addresses in Puerto Rico.

More commonly, and for the rest of this entry, we are concerned with a different meaning. Urbanisation is the name for the movement of people from rural to urban areas, and the resulting growth of cities. Urbanisation is a process that has occurred, or is occurring, in nearly every part of the world that humans have inhabited.

Causes of Urbanisation

People move into cities to seek economic opportunities. In rural areas, often on small family farms, it is difficult to improve one's standard of living beyond basic sustenance. Farm living is dependent on unpredictable environmental conditions, and in times of drought, flood or pestilence, survival becomes extremely problematic.

Cities, in contrast, are known to be places where money and wealth are centralised. Cities are where fortunes are made and where social mobility is possible. Businesses, which generate jobs and capital, are usually located in urban areas. Whether the source is trade or tourism, it is also through the cities that foreign money flows into a country. It is easy to see why someone living on a farm might wish to take their chance moving to the city and trying to make enough money to send back home to their struggling family.

These conditions are heightened during times of change from a pre-industrial society to an industrial one. It is at this time that many new commercial enterprises are made possible, thus creating new jobs in cities. It is also a result of industrialisation that farms become more mechanised, putting many labourers out of work.

Effects of Urbanisation

While it is true that opportunities exist in cities, it is also true that the competition for these opportunities is fierce. Very few people make their fortunes, and the rest must still find ways to eat and sleep while they wait for their chance. This leads to one of the most obvious effects of urbanisation - the growth of slums.

Slums

Slums are areas where large populations of extremely poor people live in sub-standard conditions. Common features of slums include:

• Land Insecurity - Slum dwellers are often 'squatters', living on land that they don't officially own. The land is often owned by the government, and there is a constant danger that it may be sold out from under its powerless inhabitants. These displacements exacerbate a poverty that is already oppressive.

• Poor Living Conditions - The houses in slums are often made of any materials at hand, which could include mud, sticks, sheet metal, cartons, and other waste materials. Crowding is typically extreme, with entire families living in one-room structures, and very little space between one structure and the next. Sanitation is often very poor, which contributes to the spread of diseases such as cholera, typhoid, tuberculosis, diphtheria, and bilharzia. Utilities such as electricity, water and sewage disposal are either not available or only available on a very unreliable basis.

• Unemployment - Since there are more people competing for jobs in the city than there are jobs available, unemployment is a constant problem. Those who are unable to find jobs find themselves wandering the slums, looking for some income-generating activity, which leads to...

• Crime - Slum conditions make maintenance of law and order extremely difficult, and patrolling the slums is not usually a priority for law enforcement officers. Crime is typically rampant, and common activities include drug trafficking and abuse, weapons trafficking, burglary, and prostitution. Criminal elements are sometimes organised into gangs, and are sometimes independent.

• Accelerated Population Growth - Recent arrivals in the city often retain the habit of having large families, which makes sense in a rural setting. In the slums, where education about family planning is not readily available, this leads to the population ballooning far beyond the capacity of the environment to support it adequately, which in turn exacerbates all of the above problems.

Environmental Impacts of Urbanisation

The growth of cities can have significant impact on the surrounding environment:

• Temperature - Due to several factors, including the paving over of formerly vegetated land and the high concentration of heat sources, cities tend to be warmer than surrounding countryside, sometimes by a difference as large as 10° Celsius. Large cities become 'regional heat islands', which can alter local weather patterns.

• Air Pollution - One of the most obvious differences between an urban and a rural area is the air quality. Due in large part to heavy motor vehicle traffic, and also to energy production, a blanket of smog hangs over many cities. This polluted air is, in addition to being quite ugly, a public health problem.

• Water Issues - When an area is urbanised, the water cycle in the area changes dramatically. First of all, cities have more precipitation than surrounding areas, with pollutants and convection currents serving as magnets for raindrop formation. Once the water falls, instead of being absorbed by the soil, it is instead channelled into run-off systems, picking up ground pollutants along the way. This pollution is added to that brought about by industrial waste and sewage disposal, which is often untreated, especially in cities of the developing world.

• Destruction of Habitat - The conversion of a natural area to an urban area means the destruction of whatever was there previously. When wetlands, for example, are paved over, an ecosystem is lost, and any species dependent on that ecosystem die out in the area. A less drastic example is that of erosion - valleys tend to contain fertile topsoil, which tends to get washed away if the valley is urbanised.

Urban Sprawl

Urban sprawl is a later stage of urbanisation. After a city has grown vertically and filled to a certain density, it begins to grow horizontally, spilling out of its previous borders in typically low density, low efficiency developments which can eventually extend over a sizeable area around the original city (think Los Angeles). Since urban sprawl is low-density, it quickly occupies a lot of space, that might have previously been used for agriculture, or just some natural habitat.

Benefits of Urbanisation

From the above, the growth of cities sounds rather grim. Why should such a destructive process be allowed to continue? One should not, however, be misled. There are many benefits to cities as well.

• Efficiency - Cities can be tremendously efficient. For example, imagine 100 families living in 100 separate houses spread out over many acres of land. Now imagine the same 100 families in a single block of flats. Obviously, in the flats, far less effort is required to supply energy, water, heating, and waste disposal to these families. Additionally, only in cities are such things as recycling programmes possible, because collection can be made so efficient.

• Convenience - In a city, everything is nearby. Access to education, health, social services and cultural events is much more readily available in a city than in a rural setting. Because things are located so closely, cities can make motor vehicle use unnecessary for many citizens. This is especially true when a city has efficient mass transportation systems in place, systems which are not feasible for rural populations.

• Concentration of Resources - Because of the density of people, wealth, and other resources in cities, many institutions become possible that would not be in areas where such things are more spread out. Basically, when enough people are put together in a small area, they start coming up with ideas to do things - cultural, political, commercial and social activities that just don't occur outside of cities. For example, without cities, there never would have been universities.

Urbanisation in the World Today

The above is the theory behind urbanisation and how it would be expected to occur. How does it actually go on in the world? The answer to this question depends on where and when it is asked.

The Developed World

In most developed countries, urbanisation took place largely in the past. It coincided to a great extent with the Industrial Revolution of the 19th Century, and is well documented in the history books. The cities of the United States and Europe grew as they were flooded with farm-workers, displaced by the mechanisation of agriculture. Eventually, the developed nations achieved their current level of urbanisation, about 70% in cities, and they have basically levelled off there. Urbanisation in the developed world now mostly takes the form of Urban Sprawl, as the cities mature, and get fat.

The Developing World

In countries called 'developing', mostly in South America, Africa and Asia, urbanisation is at the stage where it was in the developed world around the time of the Industrial Revolution. Most city growth is occurring in these nations², with examples of some of the largest and fastest growing cities being Mexico City, Lagos, and Jakarta. It is in the developing world that the greatest challenges are, as far as city planning and city management.

The Future

There is no question that urbanisation is here to stay. In 1985, 43% of the world population lived in urban areas. Population experts estimate that by the year 2025, over 60% of humans will be city-dwellers. Will these billions of people live in clean, efficient, modern cities, or will they inhabit endless slums?

The goal of urban planning is to achieve the benefits of cities without incurring all of the negative effects. This goal is sometimes referred to as 'Sustainable Growth'. How do urban planners hope to achieve sustainable growth? The most basic rule is to plan cities, rather than to let them grow naturally. When cities are planned, it can be ensured that there is adequate infrastructure to support the population, and that residential areas are located with convenient access to major transit arteries and to social services.

The actual details of city planning are beyond the scope of this entry, and would indeed be enough to fill volumes. Suffice it to say that planning cities for sustainable growth, especially in the developing world, is one of the major challenges facing humanity at the beginning of the third millennium. This issue, along with managing the continued population boom, and effecting a fair distribution of food and other resources, is central to the question what the future will look like for humans on Earth.