In 1959, the world's population was 3 billion. By October 12, 1999, it had doubled (pdf). And by the end of 2012, we will be more than 7 billion strong.
Accommodating these growing numbers has required continuous alteration of our environment. A river dammed here, a forest razed there... each little change seemed minor when it was viewed in isolation.
But Wired magazine's time-lapse videos of our impact on the landscape bring the scope of our actions into sudden perspective.
Take a look at the videos. Watch the Aral Sea shrink before your eyes. Watch Lake Powell all but disappear. And on the flip side, watch wetlands regrow in Mesopotamia.
For more satellite images of environmental change wrought by humans, visit the U.S. Geological Survey's Earthshots website.