An expression used to say 'if it becomes X' or 'if that is the case'; often implies 'since X is so' when introducing consequences or requirements.
社長が反対するとなれば、計画は中止されるだろう。
If the president objects, the plan will probably be canceled.
夏休み中に工事をするとなれば、住民への周知が必要だ。
If construction is to take place during summer vacation, residents need to be informed.
値段が上がるとなれば、売れ行きに影響が出るかもしれない。
If prices go up, sales might be affected.