Adaptation is rapidly becoming a mainstream policy response for addressing current and future climate impacts on society and the environment. Significant capital resources are currently and will continue to be invested in autonomous and anticipatory adaptation processes across a range of scales. However, the institutional arrangements for the evaluation of adaptation processes, policies and measures are still in their infancy. Therefore, though adaptation is undoubtedly proceeding, mechanisms for the development of an evidence base for evaluating its success are lacking.

A review of a diverse suite of adaptation decision frameworks and action plans revealed a range of gaps that may impede efforts to evaluate adaptation. Although evaluation and monitoring are often advocated within adaptation decision-making frameworks, methods for undertaking such work are rarely articulated. As a consequence, adaptation action plans often neglect this important component of adaptation policy development. Furthermore, adaptation plans frequently fail to acknowledge the importance of core design principles for adaptation policies and measures such as efficacy, efficiency and equity. The ultimate implication of such evaluation gaps is that communities of adaptation researchers and decision-makers are ill-equipped to track systematically progress and learning on adaptation.

As a step toward addressing these shortcomings, a general guiding framework for the evaluation of adaptation has been developed based upon tools commonly employed in development assistance projects and programs. Output and outcome-oriented evaluation methods are an intuitive and direct approach to assessing progress toward societal goals with respect to vulnerability reduction. However, difficulties in the attribution of outcomes to specific adaptation actions and outputs are likely to confound such approaches. As a supplement, the concept of adaptive capacity can be operationalised through input-oriented evaluation methods. For example, investments of capital, quality control of data and information, and the adoption of principles such as efficacy, equity and efficiency in the selection and implementation of adaptation options can provide a useful evidence base for evaluating the likelihood of adaptation actions contributing to successful outcomes.

Advancing beyond such conceptual frameworks for evaluation to their application in the development of robust evaluation protocols is dependent upon a range of future advances in adaptation research and tool development. These include the construction of databases of adaptation action plans, policies and measures; the development of adaptation metrics (both input and outcome) that can be utilised for evaluation purposes; longitudinal studies of adaptation; and the critical review of existing provisions for evaluation across a range of scales.