Of Clouds and Crowns
Rainfall and Tree Canopies in the Salish Sea Bioregion
This map explores the relationship between annual rainfall and tree canopy height across the Salish Sea Bioregion. Both variables are strongly influenced by climate, terrain, and coastal processes, yet they are rarely examined together at a regional scale. Mapping them side by side reveals where these environmental factors reinforce each other, and where they diverge.
Two very different datasets were transformed into comparable formats without diluting either variable. Regularly sized hexagons were used to aggregate average rainfall and canopy height values, providing an unbiased spatial framework. Each variable was classified into low, medium, and high categories by dividing its full range into thirds, producing nine possible combinations across the landscape.
The resulting patterns are intuitive in some places and surprising in others. Areas of high rainfall and tall canopy dominate much of the coastal and mountainous terrain, while rain-shadow regions show clear contrasts between moisture and forest structure. In several areas, tall forests persist in lower-rainfall zones, suggesting the influence of local topography, soil, or microclimate rather than precipitation alone.
The map is designed to emphasize natural systems over political boundaries. Only relevant physical features are labeled, allowing the relationship between clouds and crowns to remain the focus. Rather than explaining a single conclusion, the map invites exploration and comparison, encouraging viewers to consider how climate and landscape interact across one of the Pacific Northwest’s most complex bioregions.
This project was later featured by Maps.com as an example of accessible environmental cartography.
2025-10-23