There is a nice whitish/lime green mold growing on a 9 sq foot section of my 20-yr old flat membrane roof.   Although there is an annoying live oak above it, the tree actually overshadows the entire 400 sf porch, so i cannot figure out why it grows there.

 

Should I gently scrape it off?  Or leave it alone?

 

c on dfi, getting ready for hurricane danny and moving malia's stuffed animals to high ground