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In this final episode, Dallas examines what it takes to keep seven billion humans alive with food, energy and water. 40% of the Earth's surface is now devoted to growing food. To appreciate how we have transformed vast swathes of land to produce food, Dallas paraglides over the south coast of Spain, where what was once an arid landscape is now home to the world's largest greenhouse array. He also rides with cowboys on Brazil's largest cattle ranch, to help herd over 125,000 cattle. He visits Lake Mead, the biggest man-made lake in the USA, to see how it has helped us transform harsh desert into the bright lights of Las Vegas. He also joins the team building a 750 mile long artificial river to transport water from south to north China.

In this episode, Dallas explores how we have been redesigning the planet as we build ever more astonishing places to live. In Dubai, he climbs to the very top of the world's tallest building - over half a mile above the desert sand - to help clean the highest windows in the world; and he explores how desert wastelands have been transformed into bristling forests of skyscrapers as we've conquered the sky and turned it into a place we can call home. In China, the rate of change is accelerating as millions move into the cities; to keep pace, they have learned to erect 30-storey buildings in under three weeks. The world is changing underneath our feet too; Dallas dives beneath Mexico City with one of the two-man team whose unenviable job it is to keep the city sewers flowing, before examining a very new-world solution to this age-old problem.