Northwest Impacts & Adaptation

The Northwest is bordered by the Pacific Ocean to the west and Canada to the north. The region includes the cities of Seattle, Portland, Spokane, Boise, and Tacoma. The Cascade Mountain Range runs north-south through Washington and Oregon, splitting the region. The climate on each side of the mountain range is very different. West of the mountains, temperatures are mild year-round (days below freezing or above 90°F are relatively rare), winters are wet, and summers are dry. East of the mountains, it is typically sunnier and drier over the course of the year, winters are colder, and summers can be significantly hotter. ^[1]

The climate of the Northwest is changing. Over the last century, the average annual temperature rose by 1.5°F, with increases in some areas up to 4°F. ^[2] Changes in snowpack, streamflows, and forest cover are already occurring. Future climate change will likely continue to influence these changes. Average annual temperature in the region is projected to increase by 3-10°F by the end of the century. ^[2] Winter precipitation is projected to increase while summer precipitation is projected to decrease, though precipitation projections are less certain than those related to temperature. ^[2] Future climate change impacts would be compounded by pressures related to the region's rapidly growing population.

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Impacts on Water Resources

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Peak streamflow in the Quinault River is projected to peak earlier in the year.
Source: USGCRP (2009)

A reliable water supply is crucial for energy production, agriculture, and ecosystems in the Northwest. Much of the region's water is stored naturally in winter snowpack in the mountains. The snowpack melts and runs off into streams and rivers in the late spring and summer, a time when there is very little rainfall. Climate change will likely threaten this natural storage, with important consequences for the timing of runoff and amount of water available in streams and rivers (streamflow) throughout the year. ^[2]

• Higher winter temperatures are projected to cause more precipitation to fall as rain instead of snow. This would decrease snow accumulation. The April 1st snowpack, an indicator of natural water storage available for the warm season, is projected to decline by as much as 40% in the Cascades by the 2040s. ^[2] This reduction in available snowpack (and thus water) could increase the risk of drought during normally dry summers.
• Higher temperatures will likely contribute to earlier snowmelt and major changes in the timing of runoff. As a result, the peak of spring runoff is projected to shift 20 to 40 days earlier by the end of the century. ^[2]
• Warmer temperatures are projected to cause more precipitation to fall as rain. Overall winter precipitation is projected to increase. These changes would increase winter flood risks. ^[2]
• Changing streamflows would strain water management and worsen existing competition for water. Competing demands for water in the Northwest currently include hydropower, agricultural irrigation, municipal and industrial uses, and protection of ecosystems and threatened or endangered species. Increasing temperatures and population could increase demand and further stress urban water supplies. Meanwhile, the climate change impacts listed above could decrease supply. ^[2]
• About 70% of electricity in the Northwest is supplied by hydroelectricity. Decreasing summer streamflows would reduce hydroelectric supply and stress electricity supplies. Meanwhile, rising temperatures would increase electricity demand for air conditioning and refrigeration. ^[2]

For more information on climate change impacts on water, please visit the Water Resources Impacts page.

For more information on climate change impacts on energy, please visit the Energy Impacts page.

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Impacts on Forests, Agriculture, and Food Supply

Higher temperatures, changing streamflows, and increases in pests and disease threaten forests, agriculture, and salmon populations in the Northwest. ^[2]

• Projected climate change impacts threaten forests due to higher forest fire risk, decreasing tree growth, and increasing insect attacks. Higher summer temperatures, earlier spring snowmelt, and potential reductions in summer soil moisture would contribute to wildfire risk. Drought stress and higher temperatures would likely impede tree growth, though high-elevation forests may experience increased growth in the short term. These climate impacts would also contribute to increased frequency and intensity of attacks from mountain pine beetles and other insects. These attacks would worsen fire risk and reduce timber production. Projected climate changes will likely cause shifts in the composition, range, and even existence of Northwest tree species. ^[2]
• Decreasing supplies of water for irrigation, increasing incidence of pests and disease attacks, and growing competition from weeds threaten Northwest agriculture, particularly the production of tree fruits such as apples. ^[2]

Threatened Salmon Populations

Salmon swimming upstream.
Source: US Fish and Wildlife Service

Human activities already threaten Northwest salmon populations. These activities include dam building, logging, pollution, and overfishing. Climate change impacts would further stress these salmon populations. Salmon are particularly sensitive due to their seasonally timed migration upstream to breed. Higher winter streamflows and earlier peak flows due to climate change would damage spawning nests, wash away incubating eggs, and force young salmon from rivers prematurely. Lower summer streamflows and warmer stream and ocean temperatures are less favorable for salmon (and other cold-water fish species). These climate change impacts facilitate the spread of salmon diseases and parasites. Many salmon species are already considered threatened or endangered under the Federal Endangered Species Act. Studies show that by 2100, one third of current habitat for Northwest salmon and other coldwater fish would be unsuitable. This is because warming temperatures are projected to pass key temperature thresholds. ^[2]

For more information on climate change impacts on forests, please visit the Forests Impacts page.

For more information on climate change impacts on agriculture and food supply, please visit the Agriculture and Food Supply Impacts page.

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Impacts on Coastal Resources

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Regions of Olympia and Harbor Island that will likely be lost due to sea level rise by the end of the century.
Source: USGCRP (2009)

Climate change, particularly sea level rise, is projected to increase coastal erosion and loss of beaches in the Northwest. ^[2] The heavily populated south Puget Sound region, which includes Olympia, Tacoma, and Seattle, is one of the most sensitive regions in the Northwest to coastal erosion. ^[2]

• Some climate models project that changing wind patterns, combined with sea level rise, could accelerate coastal erosion in this region. ^[2]
• Relative sea level rise in the Puget Sound basin is estimated at about 13 inches by 2100. Some areas of the basin could experience rises of up to 50 inches (in more rapidly subsiding areas). ^[2]
• Heavier winter rainfalls could increase the risk of landslide on coastal bluffs. The combination of saturated soils and sea level rise could increase the number and severity of landslides, especially in areas with high development or already unstable slopes. ^[2]

For more information on climate change impacts on coastal resources, please visit the Coastal Resources page.

To learn more about what the Northwest is doing to adapt to climate change impacts, please visit the adaptation section of the Northwest Impacts and Adaptation page.

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References

[1] U.S. Fish and Wildlife Service (2011). Climate Change in the Pacific Northwest .

[2] USGCRP (2009). Global Climate Change Impacts in the United States . Karl, T.R., J. M. Melillo, and T. C. Peterson (eds.). United States Global Change Research Program. Cambridge University Press, New York, NY, USA.

Adaptation Examples in the Northwest

Efforts to prepare for climate change are underway in the Northwest. Many local and regional groups are already taking actions to adapt to projected declines in snowpack, streamflow changes, and sea level rise. Learn more about climate change impacts in the Northwest in the Northwest Impacts section.

Below are examples of ongoing efforts to adapt to climate change impacts in the Northwest. Following the examples, there are links to a number of adaptation plans, reports, and studies specific to the region. Both the examples and links are intended to be illustrative — they are not intended to be comprehensive.

Olympia, Washington plans for sea level rise

Olympia, Washington is located on the southern end of the Puget Sound. Source: City of Olympia (2010) (PDF)

Downtown Olympia is vulnerable to coastal erosion and sea level rise. The city published its first assessment of sea level rise in 1993. ^[1]

In 2007, the Olympia City Council renewed its efforts to address climate change and sea level rise. According to a presentation by the City (PDF), the city has gathered more accurate information about land elevations; created maps that illustrate potential high tides, storm events, and sea level rise; assessed the impacts of sea level rise on infrastructure and stormwater systems; and monitored changes in geology that would increase relative sea level rise.

For more information about the impacts of sea level rise in the Northwest, visit the Northwest Impacts section. For more information about adaptation strategies to deal with sea level rise and storm surges, please visit the Coasts Impacts & Adaptation page.

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A significant portion of downtown Olympia, Washington would be at risk of flooding with projected sea level rise. Source: USGCRP (2009)

The Swinomish Indian Tribal Community protects economic and cultural resources from the impacts of climate change

The Swinomish Indian Tribal Community includes approximately 3,000 people from several Coast Salish groups that live on roughly 10,350 acres of tidelands, forested uplands, rural areas, and urban development in western Washington. In 2009, with the technical assistance of the University of Washington Climate Impacts Group, the Tribe released the Swinomish Climate Change Initiative Impact Assessment Technical Report (PDF).

The Coast Salish people of the Swinomish Tribe have a long history that relies heavily on coastal resources. Source: USGS (2009)

The Swinomish Climate Adaptation Action Plan (PDF) proposed strategies to address risks associated with forest fires and to inundation of coastal resources. Strategies included improvements to forest management policies and practices and a variety of options for protecting costal structures or requiring development to occur farther away from the coast.

For more information about adaptation strategies for coastal communities, visit the Coasts Impacts & Adaptation page. For more information about adaptation strategies for wildfires, visit the Forests Impacts & Adaptation page.

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King County, Washington releases a Climate Action Plan

High flows on the Raging River during a November 2006 storm washed out a portion of Preston Frontage Road Bridge in King County, WA. Source: King County DOT (2006)

King County developed a Climate Action Plan (PDF) that discusses adaptation. The County also released a guidebook (PDF) to assist local, regional, and state governments in preparing for climate change.

To protect regional transportation infrastructure, the County has begun evaluating higher flows for bridges and culverts (structures commonly placed under roads to allow water to flow) and implementing educational efforts to facilitate sharing information among staff. The County is slated to train road services staff in climate change adaptation measures. ^[2] For more information about adaptation strategies for transportation systems, visit the Transportation Impacts & Adaptation page.

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The State of Oregon builds a Climate Change Adaptation Framework

In 2010, the State of Oregon released the Oregon Climate Change Adaptation Framework (PDF). The Framework provides a method for local governments and agencies to assess projected impacts and evaluate various adaptation strategies. The Framework highlights important likely impacts and offers some guidance for identifying risks, short-term priority actions, and ways to implement decisions. It was developed along with the Oregon Climate Assessment Report (PDF), which identifies the likely impacts of climate change in Oregon. In addition, the Oregon Coastal Management Program released Climate Ready Communities (PDF) in 2009, which provides specific guidance for coastal communities.

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Portland considers facility expansion due to future water supply and demand scenarios

In Portland, Oregon, most precipitation falls during the winter months. The greatest challenge for the Portland Water Bureau is supplying water during the summer months, when demand is double average daily use. ^[3] Using climate model projections, the utility generated future scenarios of water supply and demand, with consistent results including increased winter precipitation, earlier snowmelt, and drier summers. ^[4] The projected supply and demand scenarios would result in a 2.8-5.4 billon gallon decrease in reservoir storage. ^[3] To make up this deficit the utility is considering expanding groundwater supply or surface water storage.

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References

[1] City of Olympia Public Works Department (1993). Preliminary Assessment of Sea Level Rise in Olympia, Washington: Technical and Policy Implications (PDF). City of Olympia Public Works Department.

[2] King County (2007). 2007 King County Climate Action Plan (PDF). King County.

[3] Miller, K., D. Yates (2006). Climate Change and Water Resources: a Primer for Municipal Water Providers (PDF). American Water Works Association, Denver, CO, USA.

[4] Palmer, R., M. Hahn (2002). The Impacts of Climate Change on Portlands Water Supply: An Investigation of Potential Hydrologic and Management Impacts on the Bull Run System (PDF). Portland Water Bureau.