I don't think that divers depopulate the reef - unfortunately chaging climate and polution do this for us.
I can say with some certainty as a marine biologist of 40+ years that as divers we indeed can "depopulate" a reef, at least of certain species (and I'm not referring to spear fishing). We have seen examples of species here in Catalina (soCal) waters which avoid areas where divers and snorkelers are present in large numbers, yet are found in areas immediately adjacent to the areas where humans are.