This chapter takes a long-term view on global challenges by considering whether or not cooperation can develop through repeated interactions among nation-states. For acid rain, nations within a region confront the same pollution problem period after period, in which uncoordinated actions can create considerable costs to the pollution recipients. A cooperative outcome to limit these acid rain emissions would greatly benefit the nations involved. If cooperation were to develop for a particular problem, is it likely to occur at the regional or global level? When, say, cooperation initiates at the regional level, is it anticipated to diffuse to other countries and regions? These are important questions. Faced with significant regional and global challenges, successful nations may, like successful species, be those that develop strategies that maximize their fitness in terms of high payoffs. Behavioral patterns of successful nations are expected to be copied by other nations, thereby spreading throughout a region and, at times, beyond. If the diffusion is sufficient, then cooperators can “colonize” the population of nations and take over. For cooperators to last, they must be immune from invasion by opportunistic “mutants” who employ another strategy.

Consider the Prisoners' Dilemma where playing the dominant strategy would give the participants low payoffs. Subsets of nations that cooperate may capture greater payoffs and, with them, increase their long-run survival possibility. Concepts from repeated games and evolutionary games can be fruitfully applied to the study of global challenges.