More than 8 million people are crowded together to live in New York City. What makes it possible? In part, it’s the city’s great public spaces — from tiny pocket parks to long waterfront promenades — where people can stroll and play. Amanda Burden helped plan some of the city’s newest public spaces, drawing on her experience as, surprisingly, an animal behaviorist. She shares the unexpected challenges of planning parks people love -- and why it's important.