From the scorched scrabble tile spread of Mumbai slum roofs to the skyward strut of Shanghai skyscrapers, we know all too well the dilemmas global cities currently have to confront: population growth, mass sanitation, pollution and transport.

Most poignantly of all though is that half the world’s population – around 3.5 billion people – currently inhabit these cities, and by 2050 that proportion is predicted to swell to three quarters. In the new documentary film Urbanized, US director Gary Hustwit looks at how we can rise to the challenge this is creating.

The final part of a trilogy of architecture films, which also includes Helvetica (2007) and Objectified (2009), Urbanized combines bird’s eye camera work with views from the street alongside interviews with a range of city planners, mayors and renowned architects such as Sir Norman Foster and Rem Koolhaas.

Managing to bestow a message without preaching, Urbanized has got bite too. Like a diplomatic personality working between boardroom, studio and support centre group, it caters to professional architects without alienating those untrained in the language of landscape architecture.

We’re shown all sides of the prism, from the financials of architect Alejandro Aravena’s unique semi-houses in Santiago, Chile – affordable homes which families can complete themselves after moving in – to the High Line, a public park built on an historic freight rail line elevated above the streets in Manhattan.

In Detroit meanwhile, revival is coming about through local allotments and vegetable growing, while in New Orleans, ‘I Wish This Was…’ stickers plaster wounded property and derelict public buildings, each one placed there by artist Candy Chang and duly filled in by those passing by.

The film’s building air of optimism is added to by former mayor of Bogotá, Enrique Peñalosa, as he boyishly guides us around the new bicycle lanes and bus networks he dreamed up and implemented in the Colombian capital, a place renowned for its dire traffic problems.

Peñalosa is joined by Oscar Niemeyer, a 103 year-old Brazilian architect, who talks about Brasilia and its spacious, socialistic layout as well as array of curious buildings.

And what of the megacities? Naturally, Hustwit touches on places such as Mumbai, which at 12 million inhabitants, is set to become the world’s largest urban centre – but he doesn’t get bogged down with statistics, nor peddle doom.

From zealous protests at the bulldozing of a Stuttgart park to an old-fashioned community energy-saving effort in a Brighton street, Urbanized lives and breathes in the very present. Apocalyptic forecasts are out of the window and, although the Middle East is overlooked as a location, the film shows how people power is at play. Just as citizen participation is endemic in so much of our lives, in Urbanized it gives the audience a hope that seems infinitely more grounded in reality than built on idealism.

Review by Simon Cooper

Photo courtesy Swiss Dots Ltd.

Urbanized is showing at the Barbican Centre in London from 16th-23rd December 2011 and is available on DVD on 13 February 2012. Run time: 85mins.