Cities have sprung up to serve many purposes, such as commerce and manufacturing, but the key to making them more innovative could be simply to make them more livable and walkable.

In the coming decades, much of the population growth will happen in cities; by 2050 some 75 percent of the world’s population is expected to be living in them. People’s daily lives should be the main focus, says Kent Larson, an architect who directs the MIT Media Lab’s Changing Places Group. “If you design for living, you’re going to get the good stuff: the eco-friendly, green, low-carbon city,” and more innovation will spring out of the interactions of the people living and working there, Larson said Tuesday at the MIT Technology Review Digital Summit in San Francisco.

Larson argues that a few features will make highly dense but livable cities possible. One is urban farming, which could involve adding a lightweight “skin” to buildings where crops can grow in a process that is 100 times more land-efficient than conventional farming, and also uses much less water and produces much less carbon dioxide. In China alone, “you have 250 million people moving to cities, mostly farmers, and they’ll need jobs, so it’s a no-brainer,” he said.

Transportation is ripe for overhaul, too; Larson envisions micro-scale cars that can be shared, allowing for a 50-fold benefit in how much land is actually needed to accommodate parking, he said. And there could be micro-scale housing units, such as 200-square-foot apartments with various sliding units so that beds, dining room tables, and even bathrooms can expand and collapse.