I think the more pertinent question is how much of Indonesia's diet depends on the reefs. It seems like the answer is "a lot", though it's hard to get a sense of it as a proportion:
There are significant conflicts over water (https://reliefweb.int/report/world/editor-s-pick-10-violent-...). I'd expect those to extend to food too, and be acute in some regions.
I couldn't reply to the other poster (nogabebop23) that was making the point that they don't depend on reefs, but their point is moot because this is a global issue with different impacts at each latitude.