"The artist is a receptacle for emotions that come from all over the place; from the sky, from the earth, from a scrap of paper, from a passing shape, from a spider’s web." Pablo Picasso
To the best of my knowledge, this was a completely natural phenomenon, though it is in a public park that sees great amounts of people traffic. So it is possible that someone did this; next time I visit the park I will examine the tree with an even more curious eye. Thank you all for the lovely comments.
I do like this image :)