Measuring effectiveness, efficiency and equity in a Payments for Ecosystem Services trial

There is currently a considerable effort to evaluate the performance of payments for ecosystem services (PES) as an environmental management tool. The research presented here contributes to this work by using an experimental design to evaluate PES as a tool for supporting biodiversity conservation in the context of an African protected area. The trial employed a 'before and after' and 'with and without' design. We present the results of social and ecological surveys to
investigate the impacts of the PES in terms of its effectiveness, efficiency and equity. We find the PES to be effective at bringing about additional conservation outcomes. However, we also found that increased monitoring is similarly effective in the short term, at lower cost. The major difference - and arguably the significant contribution of the PES - was that it changed the motives for protecting the park and improved local perceptions both of the park and its authority. We discuss the implications of these results for conservation efficiency, arguing that efficiency should not be defined in terms of
short-term cost-effectiveness, but also in terms of the sustainability of behavioral motives. This insight helps us to resolve the apparent trade-off between goals of equity and efficiency in PES.