What would happen if humans disappeared?

Have started planning a unit for next year's end of Summer term. 

I have a number of existing sources, including 'The World without Us' and a forthcoming book from Cal Flyn.

A nice little thought experiment... They don't mention the nuclear power stations, however. I think they'd probably melt down too? More research to come - got a lot of other projects to complete as well. Here's a BBC Ideas film.