if的奇怪用法?

题目

if的奇怪用法?
The pain is being felt most keenly in the underdeveloped if resource-rich west and south-west of the country; Yunnan saw the biggest drop in growth of any province. 中间出现的if是什么意思,什么用法?句子是5月8日 经济学人的文章里的

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