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Puget Lowlands / Georgia Depression

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Map Legend & Subregion List

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NameColor on MapEPA Code*
Fraser Lowland2a
Eastern Puget Riverine Lowlands2b
San Juan Islands2c
Olympic Rainshadow2d
Eastern Puget Uplands2e
Central Puget Lowland2f
Southern Puget Prairies2g
Cowlitz/Chehalis Foothills2h
Cowlitz/Newaukum Prairie Floodplains2i

* This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.

About the Puget Lowlands / Georgia Depression

The Puget Lowlands / Georgia Depression is an ecoregion located in Washington state and British Columbia, in the lowlands surrounding Puget sound and Georgia strait, including numerous islands, peninsulas, and bays in and around the sound and strait. This region includes the US EPA Ecoregion labeled 2 or 7.1.7, as well as the Canadian ecoprovince 13.1.

Geologically, this area is a glacial trough. The climate is on the drier side of a maritime west coast climate, tending towards a Mediterranean climate in the driest locations: temperatures are moderate year-round, with weak seasonality relative to the high latitude, but precipitation is more strongly seasonal, with drier summers and wetter winters. The low elevation and rain shadow from the Olympic mountains produces slightly lower rainfall here than in the coastal areas, but moisture is still enough to support lush forest growth. Originally, this region was mostly covered with coniferous forests, with Doulgas-Fir, western hemlock, and grand fir being dominant species, as well as hardwoods including red alder and bigleaf maple. A few locally drier sites have oak woodlands.

This area is heavily populated, containing most of the population centers of Washington state, including the Seattle metro area, and the much smaller metro area around Olympia, and in British Columbia, the metro area of Vancouver, which is the third-largest metro area in Canada and the largest in Western Canada. Many of the areas that are not urbanized are heavily developed as cropland. This is the most heavily developed region in the broader Marine West Coast forests region.


1. Wiken, E., Griffith, G. "North American Terrestrial Ecoregions - Level III", Commission for Environmental Cooperation, (2011) Web.