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That’s not what case-by-case means. Wiktionary:
Separate and distinct from others of the same kind; treated individually.
Case-by-case implies that each treatment is different and is not generalisable; but the fact that they use a patient’s own tissue does not make each individual treatment different. If you want to extend the logic, you might call vaccination a case-by-case treatment as well, since they use different needles for each person.
If it is dry due to climate change I don’t see how there is an eco-system built around the drought worth preserving.