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When most people think of guerilla art they probably think of street graffiti. Sure, graffiti can be impressively creative or can even have a social or political message. However, some of the most interesting urban art installations call more directly for social change. Here are three examples of socially-motivated projects designed to make a difference.

One of the most provocative activist guerilla marking campaigns is the “it’s not happening here, but it’s happening now” campaign of the Red Cross. The organization may have a reputation for benign good works, but the Red Cross has actually engaged in a number of amazingly creative guerilla campaigns to raise awareness about various health and human safety issues around the world.

So, first you have to get past the irony of paper-made stickers to save trees. Once you do, however, you have to appreciate the simple brilliance of the These Come From Trees campaign. Studies show that these stickers reduce paper towel consumption by 15% and that a typical coffee shop uses 1,000 pounds of paper towels per year, which is the equivalent of ten trees. Quick math factoring in hundreds of thousands of cafes, gas stations and restaurants in the US quickly reveal: thousands (if not hundreds of thousands) of trees, at least, can be saved.

What place in the world could use more interstate intervention than Los Angeles? Dressed as city state employees, a set of artist decided to take matters into their own hands and install a better series of signs to aid motorists through the most congested city in the United States. Their work is well documented and has lived on in infamy, effecting positive change while also changing the status quo for guerilla communication, though most otherwise-frustrated commuters are oblivious to the aid given them by total strangers.