If 'advocacy' means the act of arguing for a cause, idea or policy and providing active support to the cause in a positive sense I advocate it. The problems that are in the process of being solved by artists like NJ at NY using techniques like situated advocacy and tactical sensing, are valid problems that when tackled produce a positive outcome. I personally feel by dedicating energy to projects that aim at improving the environmental conditions that we live in the artists are being environmental activists in some way. Collecting data from a particular park and surroundings getting an idea of what is causing the most pollution really helps to decide what is wrong. But, what happens after that, do they actually close down that chemical plant nearby? Or do they stop vehicles from plying around the park? What is actually the end result? A bunch of numbers that show that the teens have collected valuable data which now they can use to prove to the authorities that there needs to be some change around here. Calling to attention is not enough I think. In India housing colonies who have their own management just add a lot of speed-bumps around their houses along with a steel bar at the start of a road at 8 ft or so to prevent heavy vehicles entering.
But, still I could see some evidence of helping an ecosystem by creating interventions in their work. For example the fish display thingy in the Hudson river which responds to fish movement and also enhances people interactivity by having them feed the fishes with food that apparently removes bad stuff from them. I also thought such interventions might some time negate the positiveness they promulgate when people start throwing in lays chips wrappers, hot-dog packages and other crumbs of waste stuff into the river and start polluting it themselves.