The how and why of linking future scenarios across scales

A group of young scholars from a variety of disciplines, many of whom have been involved in important scenario development exercises including those of the Millennium Ecosystem Assessment (MA), published a paper last week based on an online dialogue they had about linking scenarios across scales. During their month-long online discussion, the authors reviewed a variety of scenario studies at various scales to explore how scenarios can be linked across scales and importantly, what is to be gained (or lost) in both the process and outcome by connecting scenarios at multiple scales.

Scenarios are essentially stories about the future that draw on information about the past and present, often involving qualitative and/or quantitative models, in order to explore future outcomes under a variety of different criteria (e.g. policies, practices, or social values).

Scenarios, according to the authors, “allow us to envision alternative future development pathways by taking a systems perspective and accounting for critical uncertainties such as far-reaching technological changes or changes in social values. By envisioning alternative futures, scenarios can help decision makers identify ecosystem management policies and actions that will be robust across a range of potential future outcomes, or that promote desired outcomes or characteristics, such as ecosystem resilience (Shearer 2005, Carpenter and Folke 2006).”

Multi-scale scenarios involve storylines that are developed and connected at more than one scale (e.g., local, regional, national, and global). The authors suggest such multi-scale scenarios “make it easier to examine the impacts of mismatches between the scale at which ecological processes occur and the scale at which management occurs (Folke et al. 1998, Brown 2003).” In the paper they characterize scenarios in three categories: single-scale scenarios, loosely-linked multiscale scenarios, and tightly-coupled (cross-scale) scenarios and summarize the costs and benefits of each type in the excerpt below.

“The advantage of multiscale scenarios are that they can, at least to some extent, take account of cross-scale feedbacks and differences in drivers and stakeholder perspectives at different scales. Based on our assessment of multiscale scenarios, we suggest that, if the aim is to engage stakeholders, loosely linked scenarios are generally more appropriate. Loosely linked multiscale scenarios tend to allow more freedom to explore the issues of concern to the stakeholders at each scale. In this case, any of the linking options identified above may serve as a bridging mechanism between stakeholders at different scales to understand the impact of decisions made at one scale on other scales. A major disadvantage of loosely linked scenarios is that the storylines are often inconsistent across scales and cross-scale interactions are not well accounted for. Tightly coupled cross-scale scenario exercises are more appropriate when the aim is to evaluate cross-scale processes and potential responses. We therefore suggest that tightly coupled cross-scale scenarios are most appropriate if the main objective is to further scientific understanding or to inform policy making with respect to an issue that has differential effects at different scales or has strong cross-scale interactions or feedbacks. Such fully coupled scenarios can include processes and perspectives necessary to allow an in-depth cross-scale analysis and the development of cross-scale institutional links. However, developing tightly coupled cross-scale scenarios requires a very large input of time, technical expertise, and financial resources, which should not be underestimated.”

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