'((Borders))' is by Steinunn Thorarinsdottir, a metal sculptor who seems primarily interested in featureless people in various states and positions. Originally installed outside of the U.N. headquarters, it is supposed to reflect something (or other) about multiculturalism. Passersby seem most interested in the composition of the statues. Thoraninsdottir's site is pretty cool, by the way.
Konstantin Dimopoulos's 'The Blue Trees' is meant to bring trees into contrast with their surroundings, and so remind people of them. By extension, this is supposed to bring attention to deforestation, over-logging, and the like. The actual effect is mere surreal wonderment, but anyone so confused can read the small sign standing in the middle of the park for clarification.
I'm not sure how successful these are in achieving their stated intentions, but, together (which was neither artist's decision, so far as I know), they definitely cause people to stop and wonder why the hell there are metal people and blue trees in the park. Surely, getting people to think is an accomplishment of sorts.