I googled "human-enhanced environmental catastrophes".
Guess which site came up first?
http://edro.wordpress.com/collapsing-cities/
Nothing blocked about it.
I don't see how these predictions are in any way useful. Nor do I think there is any validity to the notion that cities will "collapse", whatever they mean by that term, on a one by one basis. A city can take a pretty hard hit, such as the earthquake in Kobe, Japan, and still make it if the rest of the country is there to help. If there is a more general collapse of civilization, then all cities are in trouble because the ratio of population to resources is not favorable.