A recent article in the Guardian by Sean Thomas talks about the history of land art and three important works nearing completion: Michael Heizer's City, Charles Ross's Star Axis and James Turrell's Roden Crater (web site under construction).
While the article just barely scratches the surface of the opening question -- "Is it a monumental way to adorn the planet - or just arrogant vandalism?" -- the article is still worth a read.
Article: Guardian - This epic Earth
Other land art links:
Link: Richard Long
Link: Irish Sky Garden - James Turrell
Link: Lightning Field - Walter De Maria
Link: Robert Smithson
Link: Spiral Jetty - Robert Smithson
Reference: Andy Goldsworthy (Land+Living)
Reference:
Satell(s)iteseeing (Land+Living)