Every year on April 22, over?one billion people in 190 countries take action for Earth Day. From San Francisco to San Juan, Beijing to Brussels, Moscow to Marrakesh, people plant trees, clean up their communities, contact their elected officials, and more -- all on behalf of the environment.

Like Earth Days of the past, Earth Day 2014 will focus on the unique environmental challenges of our time. As the world's population migrates to cities, and as the bleak reality of climate change becomes increasingly clear, the need to create sustainable communities is more important than ever.

Earth Day 2014 will seek to do just that through its global theme: Green Cities. With smart investments in sustainable technology, forward-thinking public policy, and an educated and active public, we can transform our cities and forge a sustainable future. Nothing is more powerful than the collective action of a billion people.