http://tiffanyholmes.com/current-ecoart/7000-oaks-and-counting/
on follwoing paper
http://andrewjohnsonhci.blogspot.com/2010/03/nourishing-ground-for-sustainable-hci.html
http://dl.acm.org/citation.cfm?id=1518701.1518763&coll=DL&dl=ACM&CFID=43637906&CFTOKEN=18648348