Hugh Evans started a movement that mobilizes "global citizens," people who self-identify first and foremost not as members of a state, nation or tribe but as members of the human race. In this uplifting and personal talk, learn more about how this new understanding of our place in the world is galvanizing people to take action in the fights against extreme poverty, climate change, gender inequality and more. "These are ultimately global issues," Evans says, "and they can only be solved by global citizens demanding global solutions from their leaders."

Local politics -- schools, zoning, council elections -- hit us where we live. So why don't more of us actually get involved? Is it apathy? Dave Meslin says no. He identifies 7 barriers that keep us from taking part in our communities, even when we truly care.

Today, a single email can launch a worldwide movement. But as sociologist Zeynep Tufekci suggests, even though online activism is easy to grow, it often doesn't last. Why? She compares modern movements -- Gezi, Ukraine, Hong Kong -- to the civil rights movement of the 1960s, and uncovers a surprising benefit of organizing protest movements the way it happened before Twitter.

Researcher Kamal Meattle shows how an arrangement of three common houseplants, used in specific spots in a home or office building, can result in measurably cleaner indoor air.

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.

Too often, people feel checked out of politics — even at the level of their own city. But urban activist Alessandra Orofino thinks that can change, using a mix of tech and old-fashioned human connection. Sharing examples from her hometown of Rio, she says: "It is up to us to decide whether we want schools or parking lots, recycling projects or construction sites, cars or buses, loneliness or solidarity."