This visualisation of Earth - made by anthropologist Félix Pharand - shows urban areas, shipping routes, global roads and air networks. It gives a very good idea on how big our species' physical impact on the planet really is.
So big, in fact, that scientists are thinking about starting a new geological era: The Anthropocene.
The new era's name (anthropo- means human and -cene means new) refers to the effect of humans on Earth ecosystems, including the transformation of terrain and life all around us. I find it a bit too cocky - since Earth could probably wipe out any evidence of our existence in a couple thousand years and not even blink - but I guess it works given the current circumstances.
Pharand told me that "the Anthropocene has good chances to become the official name of our era. In June 2009, a new working group was established to examine the possibility of recognising an Anthropocene division either within the Holocene or separated from it." It may happen next summer in Brisbane, Australia, if the International Commission on Stratigraphy accepts it. [Thanks Félix!]