Scenarios

The Millennium Ecosystem Assessment defined scenarios as “plausible and often simplified descriptions of how the future may develop based on a coherent and internally consistent set of assumptions about key driving forces and relationships”. Scenarios are essential to explore policy responses (Response options), their likely effectiveness and trade-offs. They are often presented as narratives (storylines), underpinned by quantitative indicators regarding drivers and impacts. Scenarios can be truly contextual (i.e. describe possible changes as the result of external factors only) or take alternative policy responses already into account. Most scenario exercises build on a mix of external and policy driver assumptions.

The development of scenarios can depend on stakeholders to a varying degree. In a consultation process stakeholders are asked to comment on scenarios that have been developed independently by analysts, often using quantitative models. A participatory approach allows the stakeholders to construct their own scenario logic and corresponding storylines and quantitative elaboration. Stakeholder involvement, particularly following the participatory approach, generally increases the credibility, legitimacy and relevance of the scenarios (Process and governance).

Scenario exercises provide a structured approach to addressing related uncertainties and complexity. Generally, scenario exercises can serve different purposes: to support scientific exploration and research, to inform education and collaborative learning processes, or to underpin decision processes and strategic planning.

In the context of an ecosystem assessment, two process- and product-related outcomes are important:

First, the scenario ‘process’ can facilitate an intense learning experience for those involved, and offer a platform for a strategic conversation about future pathways. Such conversation about the future helps unveil both explicit and implicit assumptions about the unfolding of trends – and allows participants to reflect on and challenge these assumptions.

Second, the scenario ‘product’ (i.e. a set of scenarios) provides a platform to explore the implications of different assumptions about future trends with regard to ecosystems and related ecosystem services. Also, the viability and implications of different (policy) response options can be assessed against the backdrop of different contrasting scenarios.

References

• MA. 2010. Ecosystems and Human Well-Being: A Manual for Assessment Practitioners. Chapter 5 of this manual is devoted to “Scenario development and analysis for forward-looking ecosystem assessments”.
• MA. 2005. Ecosystems and human well-being, Vol. 2: Scenarios. Washington, DC: Island Press. Part 1 of this report is devoted to “State of knowledge concerning ecosystem forecasts and scenarios”.

Case-studies

• MA. 2005. Ecosystems and human well-being, Vol. 2: Scenarios. Washington, DC: Island Press.
• UK National Ecosystem Assessment (2011), chapter 26 ”Valuing Changes in Ecosystem Services: Scenario Analyses”.
• Secretariat of the Convention on Biological Diversity (2010). Global Biodiversity Outlook 3. Montréal, 94p.