Road to Rio: Rise of the sprawling cities
CNN: The past century has been defined by an epic migration of people from rural areas to the city. In 2008, for the first time in history, more of the Earth’s population was living in cities than in the countryside. The U.N. now predicts that nearly 70% of the global population will be city dwellers by 2050.
Looking back through the decades, these snapshots from space — created exclusively for CNN by NASA’s Landsat department in collaboration with the U.S. Geological Survey — reveal the impact of this vast population shift on cities around the world.
The global population explosion has hastened urban sprawl — the process of a metropolitan area expanding into the surrounding countryside, often with serious environmental consequences. These include the destruction of wildlife habitat, increased energy inefficiency and a growing dependence on motorized transport.
2000 Dubai, United Arab Emirates
With a population of 1.2 million people, Dubai is one of the few places on Earth where urban sprawl has extended into the ocean. Construction of the Palm Jumeirah, with its 17 sandy fronds (pictured at the left of 2010 image) required 110 million cubic meters of sand, according to the building firm.
Near the shore, skyscrapers line roadways and the city encroaches into the desert. Going back in time just 10 years — when the population was a little over 200,000 — earth tones predominate and the evidence of human engineering is minimal.
Las Vegas, Nevada, United States2011
These images of the Las Vegas metropolitan area show the city’s remarkable spread into the surrounding desert. Between 1984 and 2011, Las Vegas experienced rapid growth, with its population rising from 520,000 to 1.9 million.
Building and maintaining a city in the desert raises challenges, like meeting residents’ water needs. By the first decade of the 21st century, city officials had begun recycling wastewater and paying residents to remove thirsty grass lawns.
The population of Santiago, Chile’s capital, pictured here with the Andes and surrounding foothills to the east, has grown by almost two million over 25 years.
Currently home to 40% of Chile’s inhabitants, the National Statistics Institute estimates that Santiago’s population will increase by a further 1.6 million by 2031.
Santiago’s steady creep towards the foothills of the Andes has coincided with rapid glacial retreat in the region. Since 1970, glaciers in the Andes have lost 20% of their volume, according to World Bank data. The thick white patch of ice on the bottom right hand side of the 1985 satellite shot has disappeared in 2010 image.
1985Chandler, Arizona, United States2011
Chandler, Arizona, is one of the world’s most striking examples of a “boomberg” — a suburb with a population of 100,000 or more that has maintained double-digit growth over the decades. Situated on the southeastern outskirts of the Phoenix metropolitan area, it grew from just 3,799 residents in 1950 to 260,000 in 2010.
Like much of the U.S. Southwest, southern Arizona is arid, and agriculture depends on heavy irrigation. But the cultivated fields — rectangles of green and brown — pictured in 1989, have given way to the dense blues and greys of the sprawling cityscape by 2011.
According to the U.N., Iran’s capital ranks among the world’s fastest-growing cities. The metropolitan area has over 10 million residents, more than the populations of the country’s next five major metropolitan areas combined.
Whereas non-urbanized areas fringe the earlier image, urbanization fills almost the entire frame in the later shot. Major roadways crisscrossing the city in 1985 remain visible in 2009, but a constellation of additional roads has been added, particularly to the north.
This explosive growth has had considerable environmental and public health consequences, including air and water pollution and loss of arable land, according to the Global Resource Information Database.
1975 Istanbul, Turkey2011
Istanbul was home to just over two million people in 1975; by the end of 2011 its population had ballooned to more than 13 million — 18% of Turkey’s total population.
In 1973, the first bridge across the Bosporus opened — connecting the Asian side of Istanbul to the European side. The bridge is faintly visible on the 1975 image, and the urban areas in the newly connected east side are noticeably clustered around the bridge.
In 1988, Istanbul opened a second bridge across the Bosporus, visible to the north in the 2011 image. The dark grey of dense settlement has filled in the area between the two bridges on both sides of the strait.
1985 Ontario, California2010
The relatively small Californian city of Ontario (not to be confused with the vast Canadian province of the same name) doubled in population between 1985 and 2010, when it reached 171,603.
But the satellite image above is as much a story of industrialization as population growth. Formerly one of the citrus-growing capitals of the world, over the past two decades Ontario has taken advantage of its location on the outskirts of Los Angeles to become a trade and logistics centre.
As such, the numerous blocks of green and tan from 1985 have given way to the white squares and rectangles — giant warehouses and sorting depots — that predominate in 2010.
1989 Tokyo, Japan2011
Japan’s notoriously crowded capital grew from 8.3 million in 1989 to over 13 million in 2011, but this snapshot only tells a fraction of the story. During the day, Tokyo’s population increases by a further three million people, according to the government, as a result of all those commuting for work.
This satellite shot encompasses the formal boundaries of the Tokyo Metropolis. Expanding out from view, the Greater Tokyo Area — a continuous urban agglomeration that includes the adjoining prefectures of Chiba, Kanagawa and Saitama — is the world’s most populous metropolitan area, with a staggering 35 million inhabitants.
Pearl River Delta, China 2003
The Pearl River Delta in China’s southeastern coastal zone is one of the country’s economic powerhouses. The past image is from 1979 and the present image is from 2003. In 1980, China created four special economic zones to attract foreign investment in this area just north of Hong Kong, consisting of what were then the small cities of Shenzhen, Zhuhai and Shantou in Guangdong province and Xiamen in Fujian province.
The rapid growth in the region became known in China as “Shenzhen speed.” The impact on the landscape in just a quarter-century is striking: The earlier image shows few structures interrupting the lush vegetation that grows in Guangdong’s subtropical climate, while later built-up conurbations dominate.
Ouagadougou, Burkina Faso 2006
In western Africa, just south of the Sahara Desert, lies the landlocked nation of Burkina Faso. Despite the limited natural resources in this arid savannah, the nation experienced a 200% increase in urban population between 1975 and 2000, according to the United Nations Environmental Program (UNEP).
Much of that growth occurred in the capital city of Ouagadougou, where unplanned settlements sprang up along the city’s perimeter. These two false-color images show the city’s growth between 1986 and 2006, during which time the city’s population grew to 1.6 million.
These unplanned settlements may conflict with the country’s sustainable development goals and will make it harder for the government to provide basic services, such as drinking water, according to UNEP.