|''Scenarios'' are representations of possible futures for one or more components of a system, particularly, in this assessment, for drivers of change in nature and nature’s benefits, including alternative policy or management options.
Different types of scenarios can play important roles in relation to the major phases of the policy cycle, which are (i) agenda setting, (ii) policy design, (iii) policy implementation and (iv) policy review (Figure SPM 2).
“Exploratory scenarios” that examine a range of plausible futures, based on potential trajectories of drivers – either indirect (e.g., socio-political, economic and technological factors) or direct (e.g., habitat conversion and climate change) – can contribute significantly to high-level problem identification and agenda setting. Exploratory scenarios provide an important means of dealing with high levels of unpredictability, and therefore uncertainty, inherently associated with the future trajectory of many drivers.
“Intervention scenarios” that evaluate alternative policy or management options – through either “target-seeking” or “policy-screening” analysis – can contribute significantly to policy design and implementation.
"Retrospective policy evaluation scenarios" are policy evaluation scenarios employed in ex-post assessments of the extent to which outcomes actually achieved by an implemented policy match those expected based on modelled projections, thereby informing policy review.
Figure SPM 2: This figure shows the roles played by different types of scenarios corresponding to the major phases of the policy cycle. Types of scenarios are illustrated by graphs of changes in nature and nature’s benefits over time. The four major phases of the policy cycle are indicated by the labels and grey arrows outside the coloured quarters of the circle. In ‘exploratory scenarios’, the dashed lines represent different plausible futures, often based on storylines. In ‘target-seeking scenarios’ (also known as ‘normative scenarios’), the diamond represents an agreed-upon future target and the coloured dashed lines indicate scenarios that provide alternative pathways for reaching this target. In ‘policy-screening scenarios’ (also known as ‘ex-ante scenarios’), the dashed lines represent various policy options under consideration. In ‘retrospective policy evaluation’ (also known as ‘ex-post evaluation’), the observed trajectory of a policy implemented in the past (solid black line) is compared to scenarios that would have achieved the intended target (dashed line).
Methodological Approaches to scenario development
Expert-based approaches entail the use of expert opinion, knowledge (including scientific theory) or judgment to inform the various aspects of constructing scenarios and models of drivers. The term ‘expert’ implies an individual who has expertise or experience within a particular dimension through training, study or involvement in practice.
Participatory methods and tools help define complex problems related to the governance of drivers impacting particular biodiversity and ecosystem services. They also provide a platform for views to be aired, perspectives broadened, and a greater understanding of the policy issue under consideration. Participatory methods entails the inclusion of indigenous and local knowledge, which provides a more comprehensive reflection of prevailing conditions and other key inputs. It also incorporates methods and approaches that capture holistic values that people place on nature while internalizing principles and ethical values specific to their world views and realities.