Speaking of desertification, we learn of this depressing story via Boing Boing:

The Ténéré wastelands of northeastern Niger were once populated by a forest of trees. By the 20th century, desertification had wiped out all but one solitary acacia. The Tree of Ténéré, as it came to be called, had no companions for 400 km in every direction. Its roots reached nearly 40 m deep into the sand. In 1973, the tree was knocked over by a drunken Libyan truck driver. It has been replaced by a simple metal sculpture.