These photos made their way to my e-mail, unattributed, via a number of forwards. They are stunning. My best guest is that they come from photographer Michael Poliza and his Heli-Africa series. His web site is here and his flickr series here.
Update: Thanks to several readers to inform me that the pictures come from the Earth From Above series by French photographer Yann Arthus-Bertrand. A website (with downloadable wallpaper) is here. The book is here.