NbS Triple Win Toolkit: Economics and Finance 67 Review of selected intervention types Ecosystem-based Adaptation Description of intervention Ecosystem-based adaptation (EbA) is a broad intervention that can be applied in multiple contexts (e.g., urban, agricultural) and ecosystems (e.g., forests, coastal, mountains). It involves the use of biodiversity and ecosystem services as part of an overall adaptation strategy to help people to adapt to the adverse effects of climate change52. It may involve conservation, sustainable management, and/or restoration – and is especially applied to support communities dependent on natural resources and ecosystem services and vulnerable to climate change impacts53. Monetised benefits Revenue from sustainably harvested products(e.g., medicines, fuel, food) Revenue from recreation or tourism opportunities Carbon sequestration, storage or carbon markets Disaster risk reduction and prevention of natural disaster Benefit-cost ratios and cost effectiveness evidence The range of benefit-cost ratios reported is between 1.2 and 11, although some estimates can be much higher when valued in context of economic assets protected over longer timescales54. Benefits valued and valuation techniques, along with the relevant cost-effectiveness estimates, vary depending on the objectives of adaptation, but often relate to improved incomes for local communities or avoided costs from coastal protection. In particular, high benefit-cost ratios can arise where a) valuation is based on costs of damages to, or replacement costs of, coastal economic assets, and b) annual damages avoided from ecosystem-based adaptation are proportionally higher than annual maintenance costs, so longer periods of assessment typically lead to higher benefit-cost ratios. Non-monetised benefits Maintenance of local knowledge Conservation or protection of biodiversity and increased resilience Recreation potential Sustainable water management Food security Further discussion The use of the term EbA slightly predates the use of NbS, officially defined in 2009 which is the earliest use of the term in the database (see Evidence Base). It encapsulates ecological principles with a main focus on sustainable development and social benefits55,56. Much of the success of EbA comes from community-based knowledge and participation and empowerment of the local communities the intervention is intended to support. Consideration of winners and losers, disaggregating data by gender, and evaluating the vulnerability of marginalised groups (e.g., women, the elderly, disabled, Indigenous peoples) are important factors when implementing EbA57,58 but are often either overlooked in the economic assessment of EbA or noted anecdotally.