To coincide with the arrival of the world's 7 billionth person on October 31, 2011, National Geographic magazine's 2011 year-long series on world population is available on the App Store as a free app for iPad starting 10/27/11. The interactive app explores the challenges—and potential solutions—for coping with a growing human population in a world of limited resources with informative videos, interactive maps, in-depth articles, and stunning photography. The series ends with a look at City Solutions in the December 2011 issue, which will be incorporated into the app in December. Download the free app here: [Link]