This photograph was taken along the banks of the Sava River in Belgrade, Serbia. The trash mars a much-needed green space in a congested urban environment. The lost party balloons seemed a sadly appropriate counterpoint to the plastic bottles.

It has become evident that the craze for bottled water is producing one of our biggest environmental challenges. A large percentage of the bottles don't get recycled (particularly in countries without recycling programs), and as the bottled water industry continues to grow, the environmental impact will only grow worse. Ironic, given that people began drinking bottled water for health reasons, though much of the water found in plastic bottles is no safer than good tap water. In fact, much of it is tap water.