This is like one of those impossible "wife" questions with no good answer and no clean escape.
"Hey honey, if a clone of me ever replaced me, you'd be able to tell the difference right."
"Of course dear"
"Well how"
"Umm, how about XYZ"
"What if they copied XYZ too"
"ZYX?"
"ZYX! Is that what you think of me!!"
This really makes you appreciate the bazillion factors that went to making Earth a place where life can thrive.
Really sucks humans are wreaking it, and the only ones who can make a significant impact to reverse course don't care.