The smart­phone is the ulti­mate exam­ple of a uni­ver­sal com­put­er. Apps trans­form the phone into dif­fer­ent devices. Unfortunately, the com­pu­ta­tion­al rev­o­lu­tion has done lit­tle for the sus­tain­abil­i­ty of our Earth. Yet, sus­tain­abil­i­ty prob­lems are unique in scale and com­plex­i­ty, often involv­ing sig­nif­i­cant com­pu­ta­tion­al chal­lenges.