50 years after people : The roof is still green, but not in its original way. Rain and birds are working together to demolish this building. Birds would drop seeds on the roof.When it rains, plants would grow.The rain would also rust the roof.
200 years after people : The walls of 40 Wall Street are now weak from neglect and the roof is now placing an unbearable load on the skyscraper. Finally,after many years of neglect, the roof falls, destroying the rest of the walls of 40 Wall Street.