Northwest
Rising summer temperatures and changing water flows threaten salmon and other fish species.
Courtesy of NOAA
The Northwest’s economy, infrastructure, natural systems, public health, and agriculture sectors all face important climate change related risks. Impacts on infrastructure, natural systems, human health, and economic sectors, combined with issues of social and ecological vulnerability, will unfold quite differently in largely natural areas, like the Cascade Range, than in urban areas like Seattle and Portland,10 or among the region’s many Native American tribes.11,12
Seasonal water patterns shape the life cycles of the region’s flora and fauna, including iconic salmon and steelhead, and forested ecosystems.13 Adding to the human influences on climate, human activities have altered natural habitats, threatened species, and extracted so much water that there are already conflicts among multiple users in dry years. As conflicts and trade-offs increase, the region’s population continues to grow. Particularly in the face of climate change, the need to seek solutions to these conflicts is becoming increasingly urgent.
In Washington’s Nisqually River Delta, large-scale estuary restoration to assist salmon and wildlife recovery provides an example of adaptation to climate change and sea level rise. After a century of isolation behind dikes, much of the Nisqually National Wildlife Refuge was reconnected with tidal flow in 2009 by removal of a major dike and restoration of 762 acres, with the assistance of Ducks Unlimited and the Nisqually Indian Tribe. This reconnected more than 21 miles of historical tidal channels and floodplains with Puget Sound.9 A new exterior dike was constructed to protect freshwater wetland habitat for migratory birds from tidal inundation, future sea level rise, and increasing river floods.
Courtesy of Jesse Barham, U.S. Fish and Wildlife Service
Observed regional warming has been linked to changes in the timing and amount of water availability in basins with significant snowmelt contributions to streamflow. By 2050, snowmelt is projected to shift three to four weeks earlier than the last century’s average, and summer flows are projected to be substantially lower, even for a scenario that assumes emissions reductions (B1).8 These reduced flows will require trade-offs among reservoir system objectives,14 especially with the added challenges of summer increases in electric power demand for cooling and additional water consumption by crops and forests.
Climate change will alter Northwest forests by increasing wildfire risk, insect and disease outbreaks, and by forcing longer-term shifts in forest types and species. Many impacts will be driven by water deficits, which increase tree stress and mortality, tree vulnerability to insects, and fuel flammability. By the 2080s, the median annual area burned in the Northwest would quadruple relative to the 1916-2007 period to 2 million acres (range 0.2 to 9.8 million acres) under a scenario that assumes continued increases in emissions through mid century and gradual declines thereafter (A1B).6