The more closed off an ecosystem is, the more volatile and prone to change it tends to be. Yeah, birds pooping seeds in an easily-accessible forest is fine, but what about organisms in the cave who may not have developed immune systems to fight foreign contaminants? It runs the same risk as when Europeans colonized America and their diseases, which they were evolved to withstand, ended up wiping out up to 90% of Native Americans.
Don’t believe anything this goon says. Don’t believe the claims of those who stand to profit from those same claims.