"Magic ran on belief. So, when too few people were left who believed in it, magic, and all creatures magical, started to wither and die."
"Good thing the world runs on science now, eh?"
"Science is magic too, just better and more accurately described. Science knows how to transmute, and fly, and freeze, for instance."
"Oh."
"Yes. Now ask yourself, what will happen when too few people are left who believe in science ?"