Science panel hears contrasting integrated-modeling approaches that map Puget Sound's futures

Puget Sound Partnership science panel members spent a large portion of their February meeting on two integrated-modeling efforts designed to explore how land-use choices and climate change might affect the region by 2080.

The Future Scenarios team (Ross Strategic and partners) presented four character-driven narratives 'Salmon Forward, Network Growth, Rural Stewardship and Hybrid' and the Envision-based land-use simulations that illustrate each story. "The main thing we produce is a set of four character-driven narratives that describe what the future might look like," Elizabeth said, explaining that the narratives are translated into landscape changes and add-on socioeconomic models to show likely outcomes for housing, agriculture, heat exposure and habitat.

Puget Sound Institute and Puget Sound Integrated Modeling Framework (PSIMF) co-leads described a different but complementary pipeline: a chain of linked quantitative models (land-cover change, VELMA terrestrial ecohydrology, Salish Sea circulation, the ATLANTIS food-web model and a qualitative social-ecological network). Caitlin Mogul summarized PSIMF's approach and recent runs: "We run paired scenarios'status quo and riparian management'and pass outputs through VELMA and ATLANTIS to quantify flows, loads and food-web responses; results for the estuary and food web are forthcoming this year."

Both teams said their strongest value is in comparing alternatives, not in presenting a single'definitive prediction. Presenters also described common modeling assumptions (high climate change scenario, Office of Financial Management population projections for demographic inputs) and the trade-offs of scale: Future Scenarios is more nimble and scenario-driven, PSIMF produces higher-resolution biophysical outputs but requires heavier computation.

Panel discussion focused on three practical topics: the capacity to represent the benefits of dense urban redevelopment (stormwater upgrades, green infrastructure and related co-benefits), the models'treatment of housing affordability and distributional impacts, and how to present uncertainty to decision makers. Eric Strecker asked whether densification'which can prompt infrastructure improvements'is represented as a positive in models. Caitlin said PSIMF and the VELMA model can simulate stormwater infrastructure upgrades and green infrastructure effects but noted that those capabilities have not always been exploited in the current scenario runs and would likely be used at finer spatial scales.

Teams also reported socioeconomic add-ons that point to likely trade-offs: the Future Scenarios work and PSIMF add-on modules both show housing prices tend to rise under concentrated urban growth scenarios and that overburdened communities may face disproportionate effects. Presenters and panelists emphasized the need for sensitivity analyses and for better communication products that distill complex model outputs and uncertainty for planners and elected officials.

Next steps: both teams will continue planned scenario runs and follow-up analyses in 2026; panel members suggested convening targeted sessions with decision makers to test communication formats and to co-design follow-on analyses that explicitly model infrastructure upgrades or affordability remedies.