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KEY MESSAGES
<br />1. Changes in the timing of streamflow related to changing snowmelt are already observed and will
<br />continue, reducing the supply of water for many competing demands and causing far-reaching
<br />ecological and socioeconomic consequences.
<br />2. In the coastal zone, the effects of sea level rise, erosion, inundation, threats to infrastructure and
<br />habitat, and increasing ocean acidity collectively pose a major threat to the region.
<br />3. The combined impacts of increasing wildfire, insect outbreaks, and tree diseases are already
<br />causing widespread tree die -off and are virtually certain to cause additional forest mortality by
<br />the 2040s and long-term transformation of forest landscapes. Under higher emissions scenarios,
<br />extensive conversion of subaipine forests to other forest types is projected by the 2080s.
<br />4. While the agriculture sector's technical ability to adapt to changing conditions can offset some
<br />adverse impacts of a changing climate, there remain critical concerns for agriculture with respect
<br />to costs of adaptation, development of more climate resilient technologies and management, and
<br />availability and timing of water.
<br />With craggy shorelines, volcanic mountains, and high sage
<br />deserts, the Northwest's complex and varied topography
<br />contributes to the region's rich climatic, geographic, social,
<br />and ecologic diversity. Abundant natural resources — timber,
<br />fisheries, productive soils, and plentiful water — remain
<br />important to the region's economy.
<br />Snow accumulates in mountains, melting in spring to power
<br />both the region's rivers and economy, creating enough
<br />hydropower (40% of national total)1 to export 2 to 6 million
<br />megawatt hours per month.2 Snowmelt waters crops in the
<br />dry interior, helping the region produce tree fruit (number
<br />one in the world) and almost $17 billion worth of agricultural
<br />commodities, including 55% of potato, 15% of wheat, and 11%
<br />of milk production in the United States!
<br />Seasonal water patterns shape the life cycles of the region's
<br />flora and fauna, including iconic salmon and steelhead, and
<br />forested ecosystems, which cover 47% of the landscape.4
<br />Along more than 4,400 miles of coastline, regional economic
<br />centers are juxtaposed with diverse habitats and ecosystems
<br />that support thousands of species of fish and wildlife, including
<br />commercial fish and shellfish resources valued at $480 million
<br />in 2011.5
<br />Adding to the influence of climate, human activities have
<br />altered natural habitats, threatened species, and extracted so
<br />much water that there are already conflicts among multiple
<br />users in dry years. More recently, efforts have multiplied to
<br />balance environmental restoration and economic growth while
<br />evaluating climate risks. As conflicts and tradeoffs increase,
<br />the region's population continues to grow, and the regional
<br />consequences of climate change continue to unfold. The need
<br />to seek solutions to these conflicts is becoming increasingly
<br />urgent.
<br />The Northwest's economy, infrastructure, natural systems,
<br />public health, and vitally important agriculture sector all face
<br />important climate change related risks. Those risks — and
<br />possible adaptive responses — will vary significantly across the
<br />region.6 Impacts on infrastructure, natural systems, human
<br />health, and economic sectors, combined with issues of social
<br />and ecological vulnerability, will play out quite differently in
<br />largely natural areas, like the Cascade Range or Crater Lake
<br />National Park, than in urban areas like Seattle and Portland
<br />(Ch. 11: Urban),' or among the region's many Native American
<br />tribes, like the Umatilla or the Quinault (Ch. 12: Indigenous
<br />Peoples).8
<br />As climatic conditions diverge from those that determined
<br />patterns of development and resource use in the last century,
<br />and as demographic, economic, and technological changes
<br />also stress local systems, efforts to cope with climate change
<br />would benefit from an evolving, iterative risk management
<br />approach.9
<br />U.S. GLOBAL CHANGE RESEARCH PROGRAM 488 CLIMATE CHANGE IMPACTS IN THE UNITED STATES
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