NCA by Region: Northwest, Alaska & Hawai’i

Our final post in the series summarizing the regional impacts of climate change as described in the National Climate Assessment (NCA), a detailed report published by the White House in early May, focuses on the Pacific Northwest, Alaska and Hawai’i. Each of these regions is closely tied to and reliant on the natural environment, and all three have already begun to experience ecological and social impacts of climate change. For more information on regional climate change impacts you can read our posts on the East Coast, Midwest and Southwest, and overall changes to the United States from earlier in the series.

Pacific Northwest

Idaho, Oregon, Washington

The Pacific Northwest is home to very diverse landscapes whose abundant natural resources are highly dependent on seasonal changes. Specifically, snowmelt that accumulates in the mountains generates 40% of America’s total hydropower and waters crops in the interior of the region, helping to make it the number one producer of tree fruit in the world. Other flora and fauna that rely on the seasonal weather patterns include salmon and other native fish, forest ecosystems, and the human dwellers of fast growing urban areas. Climate change threatens to interrupt or shift these seasonal changes and lower summer flows of water that the ecosystems and humans rely on.

  • Earlier snowmelt reduces water flow: Observed warming has been linked to a 20% reduction in snowmelt contributions to stream flow and spring snowmelt occurring up to four weeks earlier in many parts of the region. This will further tighten the availability of freshwater for agriculture, municipal and industry use, flood control and the preservation of habitat for natural species. Meanwhile, higher temperatures will increase residential demand for water, and this added demand will require trade-offs at the reservoir level as the region’s population continues to grow.
  • Ocean acidification threatens industry: Apart from rising sea levels, the Pacific Ocean waters around the Pacific Northwest are highly vulnerable to ocean acidification as the waters absorb carbon dioxide from the atmosphere. The waters around this region are among the most acidified worldwide, especially in spring and summer. This acidification directly threatens species such as oysters, as well as those species that feed off of vulnerable species, such as Pacific salmon. Increases in ocean acidification will likely have a serious impact on the fishing industry in this region.
  • Increased wildfires, insects and tree diseases cause forest mortality: Water deficits and increased temperatures will continue the trend observed since the 1970s of a growth in the extent of wildfires in the region. Additionally, higher temperatures and drought stress will contribute to outbreaks of mountain pine beetles, a highly threatening species to Northwest pine forests. The NCA predicts that by the 2060s, 21 to 28 currently existing plant species may no longer find the Northwest habitable.


Alaska has already warmed twice as fast as the rest of the nation, causing sea ice to rapidly decline, thawing permafrost and shrinking glaciers. These changes are causing an increase in wildfires and warming oceans are threatening fisheries. While melting sea ice may generate more transportation opportunities, land-based energy exploration will be affected by a shorter season when ice roads are viable. Alaska is also home to 40% of the federally recognized native tribes who are highly vulnerable to climate impacts on traditional hunting, fishing, and cultural connections to the land and sea.

  • Arctic summer sea ice expected to disappear by 2030s: Already in Alaska, sea ice levels in September are half of what they were at the beginning of records in 1979. Reduction in sea ice lowers the earth’s albedo, increasing warming even more. The reduced ice extent will open up passageways for transportation, tourism, and fossil fuel drilling under the seafloor. In return, however, the area will be more at risk of oil spills and maritime accidents, as well as increased shoreline erosion from the added traffic. As polar bears and walruses live primarily on sea ice, this loss highly threatens their size and prevalence in Alaska.
  • Melting glaciers and warming permafrost: Melting glaciers in Alaska and the surrounding area are contributing an amount equal to 10% of the annual discharge of the Mississippi River into the oceans, and are also releasing significant amounts of organic carbon and other minerals that impact local fisheries. While melting glaciers initially increase water flow into hydro power plants, an eventual thaw will threaten freshwater supply to the area. Thawing permafrost will also remove a key source of freshwater, increasing wildfires and reducing winter habitat for caribou, a culturally and nutritionally important food source for the native people.
  • Changes in ocean chemistry impact fisheries: With Alaska already experiencing a warming of 3° F over the past 100 years, ocean acidification, rising temperatures, declining sea ice, and other environmental changes are interacting to affect the location and abundance of marine fish. Overall, habitats are expected to change, with some species able to expand into new areas unlocked by melted sea ice, but other cold-water fish limited in their habitable ecosystem. Ocean acidification will have deadly impacts on many small aquatic species low on the food chain, which will result in lower weights and prevalence of salmon and other key fisheries species that feed off of the affected small aquatic species.

Hawai’i and Pacific Islands

Hawai‘i, the Commonwealth of the Northern Mariana Islands, the Federated States of Micronesia, the Republic of the Marshall Islands, the Republic of Palau, the Territory of American Samoa, and the Territory of Guam

Comprising more than 2,000 islands in the Pacific Ocean, the U.S. Pacific Islands region will face changes that affect almost every aspect of life. Rising air and ocean temperatures, shifting rainfall patterns, changing frequencies and intensities of storms and droughts, decreased freshwater flows, rising sea level and changing ocean chemistry will create challenges for communities and ecosystems that are directly tied to the land and the sea. With one of the highest concentrations of native species in the world and incredibly diverse and unique cultures, this region will need to adapt quickly to changes to maintain these valuable ecological and cultural assets.

  • Warmer and more acidic oceans threaten coral reefs: Coral bleaching, caused by higher ocean temperatures, has already occurred in the Northwestern waters of Hawai’i, Micronesia and American Samoa. Models predict a large decline in coral cover in the Hawaiian archipelago during this century, with reefs expecting to lose 40% of their fish. These reefs in Hawai’i currently generate $385 million in goods and services annually, important revenue that will be threatened in the coming decades.
  • Decreased freshwater availability: A decline of 15% in annual rainfall has already been observed for the easternmost islands of Micronesia, although rainfall declines will vary across the region. Some islands, including the main islands of Hawai’i, may see an increase in rainfall. However for most islands, increased temperatures and decreased rainfall will lead to more prevalent droughts, with freshwater scarcity especially concerning in low-lying islands due in part to saltwater intrusion. In high-elevation islands, decreases in rainfall are already impacting freshwater ecosystems and aquatic species.
  • Sea level rise and more frequent storm surges: Recent sea level trends in the Western Pacific are higher than the global average of 8 inches since 1900, recently increasing 1.3 inches per decade. Rising sea levels will threaten coastal structures and property, groundwater reservoirs, harbor operations, airports, wastewater systems, shallow coral reefs, sea grass beds, mangrove forests that filter water, and other social, economic, and natural resources. Residential properties on low-lying islands are especially vulnerable, and migration of communities from low-lying to high elevation islands is expected to threaten cultural integrity and further stress limited natural resources in the islands.

While the regional threats of climate change across the United States are concerning, many states are already beginning to take preventative actions to adapt to the expected impacts. In addition to highlighting the risks to each region from climate change, the NCA also details out specific recommended adaptive measures for regions to help prevent significant destruction from climate change. An active approach involving the prioritization of adaptation measures throughout the country will be a key part to maintaining the vitality, industry and natural ecosystems across the United States.

Image Credit: Howcheng via Wikimedia Commons



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