Next time you're outside, look up. Trees are so ubiquitous that it's easy to take them for granted. But Urban Forests makes you stop and pay attention to the "living landmarks" standing tall in America's cities. Jill Jonnes explores the essential roles trees play in urban centers — filtering air, providing habitat, offering shade, calming nerves and more. More at: http://www.abeautiful.world/stories/urban-forests/