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Marine West Coast Forest

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Map Legend & Subregion List

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NameColor on Map
Coast Range
Puget Lowlands / Georgia Depression
Willamette Valley
Ahklun and Kilbuck Mountains
Alaska Peninsula Mountains
Cook Inlet
Pacific Coastal Mountains
Coastal Western Hemlock-Sitka Spruce Forests
Pacific and Nass Ranges

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About the Marine West Coast Forest

The Marine West Coast is a biome or climate type characterized by a mild climate with high rainfall and humidity. In North America, this ecoregion is limited to a small band along the ocean in the Pacific Northwest, from northern California up through Alaska's coast. The presence of steep mountains along North America's west coast leads to a relatively sharp transition from this region into the more climatically-variable Northwest Forested Mountains, as well as deserts in the rain shadow of these mountains.

Most of the Marine West Coast region is characterized by high rainfall and moderate temperatures year-round. Seasons are poorly-defined, although seasonality of precipitation becomes more pronounced towards the south of the region. The south of this region usually has two seasons: a drier, warmer summer, and a cooler, wetter winter; this region transitions into the Mediterranean climate of Southern California at its southern border. This pattern phases out as one moves north along the Alaskan coast, to where at the northernmost limit of this region, the summers are wetter just because the colder winter air cannot hold as much moisture. The northernmost part of this region in Alaska transitions into Tundra.

Much of this region is dominated by coniferous forests, but the region also includes numerous broadleaf trees. The moderate climate, combined with topography that creates many sheltered locations, makes this region home to some of the tallest tree species in the world, including the Coast redwood, coast Douglas-fir, giant sequoia, and western hemlock. Overall biodiversity in this region is high, especially in its warmer parts.

This region contains the major population centers of the Pacific Northwest and a large portion of the population of the west coast of North America, but it is not quite as developed as Mediterranean California or the eastern Temperate Forest region.

This forest at Gwaii Haanas National Park Reserve and Haida Heritage Site is in many ways representative of this region; its northerly location and proximity to the ocean lead to cool, humid conditions year-round, and evergreen conifers are the dominant plants. Photo © Dale Simonson, CC BY-SA 2.0