One of the important features of this urban growth has been the increasing tendency for it to give rise to megacities/primate cities - one of disproportionate size compared to next largest town/city in the region. A good example of this is Bangkok which totally dominates the development process in Thailand. It has a population of around 7 million – approximately 56% of the total urban population for Thailand – in a country which is still predominately rural. It is 50 times larger than the second city, a disparity that continues to grow, and subsequently it dominates the countries political, social and economic factors. For example around half of the doctors and two-thirds of the countries pharmacists are located in the capital while over half of all higher education institutes are found in Bangkok. This dominance means that if a person is looking to get ahead in Thailand they should move to Bangkok. However this then draws more businesses to the capital, through the increased demand, which in turn draws more migrants to the capital, due to the present of more services.
Accelerating urban growth, especially in developing countries, poses great problems as pressures build up for jobs, on transport needs and for the basic needs of all kinds, from housing to health care. Especially in developing countries where the state often provides very little in the way of basic needs the onus is left to the residents themselves. One of the main examples of this is the existence of shanty towns/squatter settlements which migrants end up in due to a lack of affordable housing. Shanty towns subsequently have an effect on the services of the city (water and electricity especially) as the residents illegally tap into the systems so they have these luxuries but they do not pay for these services so improvements to the system often have to be made to meet the new demands without any extra funding.
Unemployment is also a factor that residents often take into their own hands through the establishment of the informal sector so they have a job and an income whilst helping people meet a variety of basic needs. Increasingly the informal sector is becoming an integral part of a cities economy providing services from fresh fruit to transport to all urban residents not just the urban poor. However there is a risk that illegal operations can sprout from these informal services as small businesses work against one another pushing up crime rates. The formal sector can also be affected as higher prices drive people toward the cheaper informal sector services and eventually a cities economy may evolve to rely on the fragile informal sector rather than the more stable formal sector.
The rapid growth of urban areas, mainly in developing countries, can lead to transport problems due to the increased availability and use of cars coupled with an infrastructure that is often poorly maintained and a transport system that is often too expensive for the poorer urban residents. This often leads to the formation of paratransit modes of transport (such as rickshaws in India) through the informal sector however although they do meet some of the demand they often just add to the congestion problems. A knock on effect of this increased traffic is the increased levels of air pollution which is compacted further through the relocation of factories to cities as there is a more willing and cheap labour force especially in developing countries where although there are air pollution laws they are often not followed by the industries and the government monitoring is too lax anyway. In fact many cities face rapidly worsening environmental problems often due to the rapid urbanisation process.
Foremost is the shortage of fresh water. For example in Indonesia a third of the urban population has access to safe drinking water. The demand from the increased population soon outstrips the present supplies leading to groundwater supplies becoming used up and polluted while local aquifers get over-pumped leading to saltwater intrusion such as has happen in Bangkok where the groundwater stores have been over-pumped leading to not only a water shortage but also many the ground unstable and causing the city to sink. Water shortages can also make the disposal of waste more difficult and the impact of any waste seepage into fresh water supplies can pose serious health risks to residents.
One of the more basic needs of the population is food and up to three-quarters of all household income is spent on food. However the increased demand combined with the modernisation of the food supply system has given rise to an invasion of supermarkets and opened the market to processed foods pushing up the prices. For example in Zimbabwe the food price index rose by 167 in only three years. As a result of increased prices (and unemployment) food is a hard commodity to come by for the poor who subsequently turn to urban agriculture which is illegal and can cause damage to the environment in the form of soil erosion. This lack of food can also increase crime rates as people turn to either stealing food directly or stealing other products to exchange for food.
Overall the full force of the impact of migrants is felt mainly in urban areas in developing countries where there is often a lack of funds to combat these problems compared to urban areas in developed areas where there is usually more than enough funds available. However it is not only about the funds available. In general there is a higher level of rural-urban migration in developing countries as the quality of life is much greater in the cities than on the farms due to services and the prospect of a better quality of life (employment, housing and health care) pulling people to the cities.