As can be seen from the picture below taken yesterday by Roosevelt Island 360 , the graffiti defacing trees on Southtown’s Riverwalk lawn has been cleaned up and removed. According to RIOC President Steve Shane:
We arranged for management in Southtown to do it.
Good job by RIOC and Riverwalk management in cleaning up the trees so quickly. 
Image of Graffiti free trees from Roosevelt Island 360
As to the graffiti on the boat dock prow and a suggestion to hire local kids to clean up Roosevelt Island graffiti, a philosophical Mr. Shane reports:
We do hire local kids.
Clean up of prow only creates tabula rasa. We will do it, again.