Many forest ecosystems provide multiple goods and services to both local users (e.g. firewood, water) and to other external beneficiaries (biodiversiTY conservation, carbon sequestration). This calls for alternative approaches in the governance of these local ecosystems. Even if local users solve the commons dilemma they face regarding the optimal provision of the direct benefit, there might still be a need for introducing mechanisms that also address the externaliTY that involves those outside of the group. This paper addresses the analysis of different types of mechanisms, endogenously emerged from groups vs. externally imposed to them, when facing the typical tragedy of the commons. During 2000_2002 we conducted a series of economic experiments in several rural communities in Colombia. The sub-set reported here of 53 sessions with 265 actual users of local ecosystems, were focused specifically on the effect of external and self-governing rules for inducing cooperative behavior within groups. A group extraction or 'commons' game was used to explore how rules, formal and informal, emerge and how individual behavior responds to regulatory mechanisms aimed at solving the dilemma. Three treatments were compared to a baseline design: Two external regulations (high and low penalties, and only 20% of the players monitored), and a self-governed system where individuals were allowed to have in each round a few minutes of non-binding face-to-face communication. Surprisingly, both external regulations generated very similar results regardless of the level of the penalty, and they induced behaviors very similar to those achieved by the self-governed treatment.
