An estimated one billion people around the world mark Earth Day each April 22, making this environmental celebration one of the largest civic observances on the planet. At its hub is the Earth Day Network, the not-for-profit organization whose founders launched the first Earth Day in 1970. The Network has helped promote the event ever since. This year’s theme is "The Face of Climate Change." As VOA’s Rosanne Skirble reports, the campaign harnesses the Internet and social media to create a worldwide digital display of people, places and wildlife that have been affected by climate change.