Where does the line of "playing God" and "not-playing God" lie? If we divert rivers we are changing the way the World was originally created/developed to serve

Where does the line of "playing God" and "not-playing God" lie? If we divert rivers we are changing the way the World was originally created/developed to serve our needs. Is a beaver then messing with nature when it builds a dam? If we use fire to create alloys out of metals is that principally different to creating synthetic plastics out of oil-based chemicals? When we selectively breed animals and crops for our satisfaction is that more natural than selectively breeding at a cellular level?