There were other methods that could have prevented starvation: the British could have closed Irish ports for export, so that the food raised in Ireland stayed there to feed the Irish. Instead, the British continued exporting food from Ireland. They could also have forbidden the distillation of grain (a potential food source) into whiskey, but they didn't, although some distilleries shut down as depopulation led to lower demand.

Having now checked the wikipedia page, that doesn't seem like it would have made a particularly big difference. The imports dwarfed the exports, particularly during 1847 when they were 8x larger.