The midi-chlorians are a sensitive topic for many Star Wars fans, I can imagine there are those who regard the original trilogy as the only canon and refuse to acknowledge the prequel trilogy. One of the main causes is the introduction of the midi-chlorians.
However, as far as I remember, there is no mention in any of the movies that the midi-chlorians are actually the cause of the Force abilities. From that scene in the move you could also interpret that the high midi-chlorian count is an indicator of Force abilities (or the potential for Force abilities).
Can it be, that it is only an indicator? For example, there are bacteria which thrive in acidic environments, or others that thrive in basic or saline environments, so maybe midi-chlorians thrive better in "Force-able" environments?
Is there anything in canon which answers this question? It seems the wiki and others sites take for granted that midi-chlorians are the cause of the Force, but without mentioning any proof.