While nobody paid much attention

 Nobody paid much attention
 as the forest grew thinner
 for humanity was a winner
 
 Then when the trees were all gone
 and the earth left absolutely bare
 they realized it was too late to care

The people living on Easter Island cut down all the trees on the island until there were none left. Then they no longer had any supply of timer to build boats to go fishing, fuel their fires or build houses. They simply did not notice they were cutting down the trees more rapidly than they were being naturally reproduced until there were none left.