Speculations – what might have been and what might be

An Earth without water?
http://astrobiology.nasa.gov/ask-an-astrobiologist/question/?id=733
What would planet Earth be like with no water – well there would be no need for this book for a start!

An Earth without Man?
http://environment.newscientist.com/article/mg19225731.100.html
One of a number of recent attempts to assess the global impact of human beings on the planetary ecosystem.