A scenario is a plausible, simplified, synthetic description of how the future of a system might develop, based on a coherent and internally consistent set of assumptions about key driving forces and relationships among key variables. (Millenium Ecosystem Assessment, 2005)

More simply put, a scenario describes a possible future. The real value of scenarios comes from the deeper understanding of the forces driving future change that emerges during the process of creating scenarios. Scenario planning is an exploratory tool (possibly an art), that has been used in a variety of contexts, e.g., Shell Group has housed a Scenarios research team for over thirty years, RA members along with others developed a set of scenarios for the Northern Highlands Lake District in Wisconsin to explore alternative visions for the future of the area, and more recently the Millenium Ecosystem Assessment explored four scenarios based on different approaches for managing ecosystem services under growing human demand.

Resources

ECOSYSTEMS AND HUMAN WELL-BEING: SCENARIOS
Findings of the Scenarios Working Group; Millennium Ecosystem Assessment Series
www.maweb.org

Ecology and Society Special Feature: Scenarios of global ecosystem services
Guest Editors: Garry Peterson, Stephen Carpenter, and Elena Bennett
http://www.ecologyandsociety.org/viewissue.php?sf=23

Shell Global Scenarios to 2025
www.shell.com/scenarios