Wiping out through famine around 30 million people with the "back to the land" agrarian policy of Mao, during the rather ironically-titled "Great Leap Forwards" *chortle* was one famine that was totally man-made.
It was such a stunning success that the Cambodians repeated it a few years later.
If you've ever worked in China, you come to understand that there is'nt a great deal that these people can't f#ck up.