Facet_wrap expects a formula as its first argument, so I'd just coerce it with as. Formula and feed in my sp as a string.
Your function worked fine for me unmodified if I just used sp='Species', i.e. The name of the variable you want to facet by.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.