I'm not sure why you're being moderated down. The conditions causing the Potato Famine to have such devastating consequences are known to be a political issue rather than than an ecological one.
I generally just assume that it's common knowledge that it was genocide by neglect, and was copied and improved upon by Germanic efficiency 80 years later. As evil as the holocaust was, the groundwork was laid by the British (and Canadians/Americans) the century before.
Wikipedia has a fairly extensively referenced article on the issue http://en.wikipedia.org/wiki/Great_Famine_(Ireland). See 'Causes and contributing factors'.