Evaluating the effectiveness of sector-specific policies relative to the planetary boundaries

There is a need for policies to address and reduce the pressure from human activities on the Earth system. Holistic assessment methods are needed for evaluating the potential of policies to contribute to reducing pressures to within sustainable levels. Absolute Environmental Sustainability Assessment (AESA) methods can be applied for evaluating environmental outcomes of policies and their effectiveness towards achieving environmental sustainability targets. In this study, an AESA is applied to evaluate the effectiveness of policies on the energy and transport sector in Tonga. Environmental impacts were estimated for three different policy scenarios, i.e. Baseline, Business-as-usual, Tonga Energy Efficiency Master Plan (TEEMP), and Transformational Change. By relating the impacts to an assigned share of the planetary boundaries for Tonga, we were able to evaluate the effectiveness of the policies and to which extent these contributed to staying within the planetary boundaries. Compared to the Business-as-usual scenario, a 40 % and 65 % reduction in climate change related impacts was achieved in the TEEMP and Transformational Change scenarios, respectively. The TEEMP and Transformational change scenarios allowed for reducing impacts to within the share of the planetary boundaries assigned to Tonga for all impact categories, except for climate change. This indicate that more stringent policies are required to achieve sustainability climate-wise. Especially, when considering the additional impacts associated with other industry sectors in Tonga. Conclusively, this study shows that AESA can be used for evaluating policies and contribute to selecting the most efficient policy and identifying how policies contribute to achieving environmental sustainability targets.