Potential contribution of prioritized spatial allocation of nature-based solutions to climate neutrality in major EU cities

Abstract We assessed the mitigation potential of nature-based solutions (NbS) within commonly overlooked pathways, including human behavioral interventions and resource savings, in addition to the well-understood carbon sequestration area. We found that general NbS implementation in the residential, transport, and industrial sectors of European cities can reduce urban carbon emissions by up to 25%. Based on spatial patterns of carbon emissions and the local context of each city, we then prioritized spatial allocation of different types of NbS implementations within 54 major EU cities, in order to maximize the carbon emissions reduction potential. We found that prioritized NbS could reduce human activity-related carbon emissions by on average 17.4% for all cities, with 8.1%, 14.0%, and 9.6% reduction in the residential, industrial, and transport sector, respectively, while 5.6% of the remaining carbon emissions could be captured by carbon sequestration. Projections to 2030 showed that prioritized NbS implementations on all available land parcels in the RCP 1.9 scenario would reduce total carbon emissions by on average 62.5% (95% CI: 47.9–66.7%) compared with the baseline scenario, with NbS capturing 22.0% marginal emissions and sequestration capturing 13.3%. Some pioneering cities climate action are projected to be very close to achieve carbon neutrality by 2030 while 3 cities can realize the goal. For carbon neutrality, cities therefore need to co-integrate indirect (human behaviors and resource saving) and direct (sequestration) contributions of NbS into aggressive climate action plans.