A study of two Canadian public school grounds, one richly biodiverse and one relatively barren, found that on the biodiverse school ground, the children had richer outdoor experiences, their use of the outdoor environment was more complex, and they had more opportunities for functional, constructive, and symbolic play as well as places for reflection and conversation.
Samborski, Sylvia. (2010). Biodiverse or barren school grounds: their effects on children. Children Youth and Environments, 20(2), 67-115.