if 在此为连词,意思为“即使,纵然”,可以换成 "even though"不对吧？变为even though 意思解释不通。if 在此是针对underdeveloped，表达意思为：即使资源丰富，但依然欠发达的...

如果 if 换成 "even though"，句型也须稍加变化，成为：

The pain is being felt most keenly in the west and south-west of the country where they are underdeveloped even though they are resource-rich.