Rapid economic impact assessment of nature-based solutions: Illustration of a co-constructed approach

Amongst the multiple advantages attributed to nature-based solutions (NBS) over conventional and grey infrastructure, is their characterisation as economically efficient, i.e. that the benefits that they generate outweigh their costs. However, surprisingly little attention has been paid so far to generating quantified evidence to support this claim in the form of comprehensive cost-benefit analysis informing actual and specific environmental decisions in given territories. In the absence of such evidence, current enthusiasm for NBS might result in unfavourable decisions, disappointment and abandonment. In this paper, we illustrate a co-constructed approach developed in close collaboration with policy-makers and involving a range of stakeholders. This approach formally evaluates the well-being impacts of adopting NBS versus non-NBS alternatives for the mitigation of agricultural impacts in the ecologically stressed Mar Menor lagoon (Spain), building-up the evidence base of the economic efficiency of NBS. More importantly, the paper illustrates how to undertake rapid economic impact assessments that, when exposed and co-constructed with a range of stakeholders in participatory processes, can support complex policy decisions in response to climate and environmental emergencies in ways that are robust, transparent and socially acceptable. By maintaining scientific rigor while simplifying data demands, rapid co-constructed economic impact assessments can not only integrate ecosystem services and economic efficiency reasoning into environmental governance but can also serve as boundary objects for consensus building, awareness raising and collective experiential learning. This is of particularly critical importance in times of growing polarisation over environmental challenges.