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The potential for large-scale afforestation, as a climate change mitigation strategy, has led to national afforestation targets being proposed. These targets raise many questions, including how to optimise carbon storage, whilst enhancing other ecosystem services (ES). Here, we assess how decision-making at different scales might affect the spatial distribution of new tree planting in England and hence ES provision. This was achieved by modelling the impact of afforestation on three example ES (carbon sequestration, recreation, and flood mitigation) to identify the best areas for planting at five scales of decision-making: national, regional, county, district, and parish. The modelling shows that carbon sequestration rates are relatively invariant across England (once unsuitable areas are excluded), whilst recreation and flood mitigation are more spatially variable, so full simultaneous optimisation of the three ES is not possible. Consequently, recreation and flood mitigation are also more impacted by changes in planning-scale than carbon, with the modelling showing over 200% difference between the parish and national-scenarios for flood mitigation benefits. Overall, targeted afforestation at national scale maximises ES benefits, but risks overwhelming some landscapes with trees. Targeting afforestation using smaller planning units generates more evenly distributed planting, but lower ES benefits. Our results show national-scale planning produces over 35% more combined ecosystem value than planning at parish-scale, and over 65% more than randomized planting. This highlights the benefits of targeting at a relevant scale, but also the potential trade-offs between widely-distributed new tree planting (e.g., parish-scenario), versus planting to optimise ES provision (e.g., the national-scenario). These results do not imply a single 'correct' scale for planning, but instead highlight the importance of considering the impact of a specific scale on the different ES, and that even spatial targeting at the smallest scale produces higher ES benefits than random planting. • Spatially targeting afforestation optimises provision of multiple ecosystem services. • Optimisation method demonstrated for national afforestation targets. • Substantial increase in ecosystem services over untargeted afforestation. • Service provision varies widely with governance level used to plan afforestation. [ABSTRACT FROM AUTHOR]

To limit global warming to 1.5 °C, vast amounts of CO 2 will have to be removed from the atmosphere via Carbon Dioxide Removal (CDR). Enhancing the CO 2 sequestration of ecosystems will require not just one approach but a portfolio of CDR options, including so-called nature-based approaches alongside CDR options that are perceived as more technical. Creating a CDR "supply curve" would however imply that all carbon removals are considered to be perfect substitutes. The various co-benefits of nature-based CDR approaches militate against this. We discuss this aspect of nature-based solutions in connection with the enhancement of blue carbon ecosystems (BCE) such as mangrove or seagrass habitats. Enhancing BCEs can indeed contribute to CO 2 sequestration, but the value of their carbon storage is low compared to the overall contribution of their ecosystem services to wealth. Furthermore, their property rights are often unclear, i.e. not comprehensively defined or not enforced. Hence, payment schemes that only compensate BCE carbon sequestration could create tradeoffs at the expense of other important, often local, ecosystem services and might not result in socially optimal outcomes. Accordingly, one chance for preserving and restoring BCEs lies in the consideration of all services in potential compensation schemes for local communities. Also, local contexts, management structures, and benefit-sharing rules are crucial factors to be taken into account when setting up international payment schemes to support the use of BCEs and other nature- or ecosystem-based CDR. However, regarding these options as the only hope of achieving more CDR will very probably not bring about the desired outcome, either for climate mitigation or for ecosystem preservation. Unhalted degradation, in turn, will make matters worse due to the large amounts of stored carbon that would be released. Hence, countries committed to climate mitigation in line with the Paris targets should not hide behind vague pledges to enhance natural sinks for removing atmospheric CO 2 but commit to scaling up engineered CDR. [ABSTRACT FROM AUTHOR]