|Cairo is the largest city in Africa, ranked by urban population, and Egypt is the third most populous country. In 1850, Cairo's population was only 250 000; 80 years later it had reached one million. Growing continuously, the population of the Cairo metropolitan area increased from less than six million in 1965 to more than ten million in 1998. Estimates of the city's current population vary widely, with some reaching as high as 16 million people.|
The Nile River is the lifeblood of Egypt as it is the main source of freshwater for household use and irrigation, a source of power from the hydroelectric facility at Aswan, and a means of transportation for people and goods. The only arable regions in Egypt are the green floodplains that line the Nile River.
Phenomenal population growth in the 20th century has resulted in the loss of much of the critically needed arable land around Cairo to urban development. The urban extent of Cairo (gray areas) expands dramatically between the 1972 and 2005 images, both into the Arabian Desert to the east and into the lush agricultural areas (green) surrounding the Nile. Most of Cairo's physical growth, particularly its unplanned or informal settlements, has been concentrated on agricultural land.
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