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  • Today ,more than half of all people in the world

  • live in an urban area.

  • By mid-century, this will increase to 70%.

  • But as recently as 100 years ago,

  • only two out of ten people lived in a city,

  • and before that, it was even less.

  • How have we reached

  • such a high degree of urbanization,

  • and what does it mean for our future?

  • In the earliest days of human history,

  • humans were hunter-gatherers,

  • often moving from place to place

  • in search of food.

  • But about 10,000 years ago,

  • our ancestors began to learn the secrets

  • of selective breeding

  • and early agricultural techniques.

  • For the first time,

  • people could raise food

  • rather than search for it,

  • and this led to the development

  • of semi-permanent villages

  • for the first time in history.

  • "Why only semi-permanent?" you might ask.

  • Well, at first, the villages still had to relocate

  • every few years

  • as the soil became depleted.

  • It was only with the advent of techniques

  • like irrigation and soil tilling

  • about 5,000 years ago

  • that people could rely on a steady

  • and long-term supply of food,

  • making permanent settlements possible.

  • And with the food surpluses

  • that these techniques produced,

  • it was no longer necessary for everyone to farm.

  • This allowed the development

  • of other specialized trades,

  • and, by extension, cities.

  • With cities now producing surplus food,

  • as well as tools,

  • crafts,

  • and other goods,

  • there was now the possibility of commerce

  • and interaction over longer distances.

  • And as trade flourished,

  • so did technologies that facilitated it,

  • like carts,

  • ships,

  • roads,

  • and ports.

  • Of course, these things required even more labor

  • to build and maintain,

  • so more people were drawn

  • from the countryside to the cities

  • as more jobs and opportunities

  • became available.

  • If you think modern cities are overcrowded,

  • you may be surprised to learn

  • that some cities in 2000 B.C. had population densities

  • nearly twice as high as that of Shanghai or Calcutta.

  • One reason for this

  • was that transportation was not widely available,

  • so everything had to be within walking distance,

  • including the few sources of clean water

  • that existed then.

  • And the land area of the city

  • was further restricted by the need for walls

  • to defend against attacks.

  • The Roman Empire was able to develop infrastructure

  • to overcome these limitations,

  • but other than that,

  • modern cities as we know them,

  • didn't really get their start

  • until the Industrial Revolution,

  • when new technology deployed on a mass scale

  • allowed cities to expand and integrate further,

  • establishing police,

  • fire,

  • and sanitation departments,

  • as well as road networks,

  • and later electricity distribution.

  • So, what is the future of cities?

  • Global population is currently more than 7 billion

  • and is predicted to top out around 10 billion.

  • Most of this growth will occur

  • in the urban areas of the world's poorest countries.

  • So, how will cities need to change

  • to accommodate this growth?

  • First, the world will need to seek ways

  • to provide adequate food,

  • sanitation,

  • and education for all people.

  • Second, growth will need to happen

  • in a way that does not damage the land

  • that provides us with the goods and services

  • that support the human population.

  • Food production might move

  • to vertical farms and skyscrapers,

  • rooftop gardens,

  • or vacant lots in city centers,

  • while power will increasingly come

  • from multiple sources of renewable energy.

  • Instead of single-family homes,

  • more residences will be built vertically.

  • We may see buildings that contain everything

  • that people need for their daily life,

  • as well as a smaller, self-sufficient cities

  • focused on local and sustainable production.

  • The future of cities is diverse,

  • malleable,

  • and creative,

  • no longer built around a single industry,

  • but reflecting an increasingly connected

  • and global world.

Today ,more than half of all people in the world

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B1 TED-Ed permanent sanitation growth people population

【TED-Ed】Urbanization and the evolution of cities across 10,000 years - Vance Kite

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    阿多賓 posted on 2014/03/18
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