Uncontrolled physical expansion of cities

In the UK, urban sprawl has consumed close to two million acres of farmland since the second world war. The Council for the Protection of Rural England estimated in 1993 that the current rate of countryside loss is now over 10,000 acres a year (twice the figure given by the government). At this rate, by 2050, one fifth of England would be urbanized, against the present 15%.

In many developing countries, inter-city and rural-urban migration coupled with the natural growth of the urban population are causing cities to expand faster than the municipality can cope with. Unplanned urban expansion results in the creation of informal settlements and slum areas and causes a twofold problem. First, it decreases fertile agricultural land, and second, the disposal of both sewage and solid waste into irrigation canals creates negative environmental and operational effects on farming activities in the vicinity. For farmers the two main problems are pollution of irrigation water and the blockage of irrigation water pipes and openings.

The private New York Regional Plan Association, in 1929 and 1968 reports, called uncontrolled growth the greatest threat to the New York - New Jersey - Connecticut region. Officials failed to listen. Land was devoured 12 times faster than population grew. Suburbia became the region's engine of growth.