Recent attempts at climate change cooperation highlight the limited efficacy of large-scale agreements when commitment to climate change mitigation is costly and initially rare. One reason is that many ecosystem services are public goods, incentivizing participants to free-ride on others’ mitigation efforts. Additional incentives to delay mitigation include actors waiting for others to develop mitigation technology and infrastructure (i.e., economies of scale) and waiting for rivals to invest in mitigation first and give up their competitive advantage. Game-theoretic work predicts greater cooperation when laws or trade agreements (‘institutions’) incentivizing mitigation are localized, which reduces the number of interacting players and the potential for free-riding. However, the greater potential for such bottom-up approaches to achieve mitigation locally can trade off with a much longer time to achieving system-wide mitigation, as mitigation spreads slower in more distributed systems. How fast societies mitigate environmental impacts can determine conservation outcomes, namely when impacts are either irreversible (e.g., greenhouse gas emissions, species extinction, rainforest loss) or exceed ecosystem tipping points. Focusing on climate change as an example, we use an individual-based model to ask whether combining regional and global institutions that incentivize mitigation can consistently promote both the chance and pace of worldwide mitigation.
Results/Conclusions
We find that a multifaceted approach starting with regional institutions and then switching to global institutions best promotes climate mitigation. Consistent with recent climate negotiations, mitigation fails to take off in simulations using global institutions from the outset, whereas an initial focus on regional institutions helps ‘lock-in’ mitigation within early-adopting regions. Once mitigation is sufficiently common, however, a timely switch from local to global institutions allows early-adopting regions to promote mitigation in the remaining, holdout regions. As a result, switching to global institutions under reasonable parameter regimes halves the time needed to reach worldwide climate change mitigation and reduces greenhouse gas emissions by 26% over 100 years when compared with bottom-up approaches utilizing regional institutions only. This benefit of gradually up-scaling institutions over exclusively regional approaches increases (3.5 times faster mitigation, 55% emissions decline) when economies of scale in mitigation and rivalry among groups further inhibit mitigation adoption and create holdout regions of late adopters. More generally, our results highlight the importance of coordinating local and global efforts to incentivize mitigation in achieving conservation goals.