Then the area should have to be replanted without granting new credits. It's perfectly natural that trees die and are replaced by new ones in a forest. The unusual thing is just the entire forest dying at the same time.
Pyrophilic species can even benefit from forest fires with reproduction being triggered by them.
It would also be quite unusual for accountant teams to follow individual trees around throughout their lifecycle, ticking little boxes when they die or something, in order to follow through on carbon credits. Think about this realistically.