In the mid-1800s, the poorest people in Ireland ate almost nothing but potatoes. Other crops were for selling. So when a blight cut a swath through the potato crop, the impact was severe, and politics played a significant role in the tragedy.
The history lesson kids often get on the Irish Potato Famine could be summed up as "a blight destroyed the potato crops, and a lot of people starved or moved away." Most kids ask, "Why didn't they eat something else?" Good question.