This TED Talk features mega cities expert Robert Mugga, recorded live at TED Global NYC 2017.

So here's a prediction. If we get our cities right, we just might survive the 21st century.

We get them wrong, and we're done for. Cities are the most extraordinary

experiment in social engineering that we humans have ever come up with. If you live in a city,

and even if you live in a slum, which 20% of the world's urban population does, you're likely to be

healthier, wealthier, better educated, and live longer than your country cousins.

There's a reason why three million people

are moving to cities every single week.

Cities are where the future happens first.

They're open, they're creative, they're dynamic, they're democratic,

they're cosmopolitan, they're sexy. They're open, they're creative, they're dynamic, they're democratic, they're cosmopolitan, they're sexy.

They're the perfect antidote to reactionary nationalism.

But cities have a dark side.

They take up just 3% of the world's surface area,

but they count for more than 75% of our energy consumption,

and they emit 80% of our greenhouse gases.

There are hundreds of thousands of people who die in our cities

every single year from violence,

and millions more who are killed as a result of car accidents and pollution.

In Brazil, where I live, we've got 25 of the 50 most homicidal cities on the planet.

And a quarter of our cities have chronic water shortages, and this in a country with 20%

of the known water reserves. So cities are dual-edged.

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