Overview: 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.