Holistic valuation of Nature-Based Solutions accounting for human perceptions and nature benefits.

When assessing strategies for implementing Nature-Based Solutions (NBS), it is paramount to identify and quantify all benefits for securing better, informed decisionmaking. Nevertheless, there appears to be a lack of primary data for linking the valuation of NBS sites with the preferences and attitudes of people interacting with them and their connection to supporting efforts to reduce biodiversity loss. This is a critical gap, as the socio-cultural context of NBS has been proven to play a big role in NBS valuation, especially for their non-tangible benefits (e.g. physical and psychological well-being, habitat enhancements, etc.). Consequently, through cocreation with the local government, we co-designed a contingent valuation (CV) survey to explore how the valuation of NBS sites may be shaped by their relationship with the users and the specific respondent and site characteristics. We applied this method to a case study of two distinct areas located in Aarhus, Denmark, with notable differences related to their attributes (e.g. size, location, time passed since construction). The esults obtained from 607 households in Aarhus Municipality show that the personal preferences of the respondent are the most relevant driver of value, surpassing both the perceptions linked to the physical features of the NBS and the socio-economic characteristics of the respondents. Specifically, the respondents attributing most importance to nature benefits were the ones assigning a higher value to the NBS and being willing to pay more for an improvement of the nature quality in the area. These findings highlight the relevance of applying a method assessing the interconnections between human perceptions and nature benefits to ensure a holistic valuation and purposeful design of NBS.

Knowledge gaps and future research needs for assessing the non-market benefits of Nature-Based Solutions and Nature-Based Solution-like strategies.

Nature-Based Solutions (NBS) can be defined as solutions based on natural processes that meet societal challenges and simultaneously provide human well-being and biodiversity benefits. These solutions are envisioned to contribute to operationalizing sustainable development strategies, especially in the context of adaptation to climate change (e.g. flood risk reduction). In order to quantify NBS performance, ease their uptake and advocate for them as alternatives to "business-as-usual" infrastructures, a comprehensive, holistic valuation of their multiple benefits (multiple advantages and disadvantages) is needed. This entails quantifying non-market benefits for people and nature in addition to determining the (direct) cost-benefit of the risk-reduction measure. Despite the importance given to the assessment of non-tangible benefits for people and nature in the literature, systematic data collection on these dimensions seems to be missing. This study reviews publications that used stated preference methods to assess non-market human benefits of NBS and NBS-like strategies. Its aim is to highlight any biases or knowledge gaps in this kind of evaluation. Our results show that the valuation of non-tangible benefits of NBS (e.g. increased recreation and well-being, enhanced biodiversity) still suffers from a lack of common framing. Despite some steps being taken on enabling interconnected benefit assessments, unexploited opportunities concerning the integrated assessment of non-market human and nature benefits predominate. Moreover, the research to-date appears based on a case-to-case approach, and thus a shared holistic method does not emerge from the present literature, potentially delaying the uptake of NBS. We argue that future research could minimize missed opportunities by focusing on and systematically applying holistic benefits assessments. Methods based on stated preference surveys may help to ensure holistic approaches are taken, as well as contributing to their replicability and application when upscaling NBS.