Widespread change is expected to make it increasingly difficult for public lands to meet the needs of the hikers & hunters, water users, tribes, ranchers & growers and wildlife that depend on them. The combined effects of climate variability and change will bring significant changes to Northwest water resources, forests, species and ecosystems, oceans and coasts, infrastructure, agriculture and human health.
Hydrology and Water Resources
Increasing temperatures and changing precipitation patterns are expected to dramatically affect water supply, water demand and water quality. The combination of increased winter rainfall and decreased winter snowfall and snow accumulation, along with changes in the timing of snowmelt and glacial melt, is likely to alter seasonal stream flow and flood risk. These factors are expected to cause higher winter stream flows and lower summer stream flows in many rivers, as well as higher summer stream temperatures. Frequent summer water shortages are expected in certain areas, leaving less water available for uses such as agricultural irrigation. These widespread changes in our regional water supply will create challenges for many of our region’s ecosystems, fish, wildlife and human communities.
Projected changes in climate threaten the productivity of the Northwest’s ecologically and economically important tree species. Increasing temperatures, declining snow accumulation and changes in soil moisture are likely to alter the growth and distribution of Northwest tree species. Increased forest mortality is also expected as a result of increasing drought stress, insect pests, diseases and wildfire. As is the case for much of the western United States, wildfires are of particular concern, as the frequency and extent of wildfires are projected to increase in the future. These fires have the potential to threaten property, human lives and important habitat areas; increase soil erosion and sediment in streams; negatively affect various industries and lead to major public health and safety concerns.
Species and Ecosystems
By the end of the century, the ranges of many plants and animals in the Northwest are expected to shift substantially as changes in temperature and precipitation alter habitat suitability. Many species may not be able to adjust their ranges quickly enough to remain in suitable habitat, in part because of the fast pace of projected change and in part because of movement barriers presented by human land use. This is likely to result in changes in Northwest regional plant and animal communities and potential regional species loss. Climate change impacts on important regional habitats, including wetlands, sagebrush-steppe, prairies, alpine tundra, subalpine habitats and aquatic habitats, will also affect the wildlife species dependent on them. For example, as stream temperatures increase, challenges are expected for fish species dependent on cold water habitat, including salmon, trout and steelhead. Federally-listed endangered and threatened species are of great concern, as they are especially sensitive to changes in temperature and habitat.
Coasts and Oceans
The effects of sea level rise, ocean warming and ocean acidification associated with climate change will continue to pose major challenges to Northwest coasts. Rising sea levels increase the likelihood of erosion and permanent flooding of low-lying coastal areas, threatening infrastructure and habitats such as coastal wetlands. The combination of sea level rise, ocean warming and ocean acidification associated with climate change will also threaten a diversity of marine species, including commercially important species and the industries that rely on them.
Climate change is expected to affect the lifespan and performance of built infrastructure (bridges, highways, buildings, etc.) in the Northwest. Climate change impacts are expected to increase the potential for damage and service disruptions to infrastructure, creating higher operating costs. On the coast and in floodplains west of the Cascades, infrastructure will be especially at risk of damage from sea level rise and increased flooding.
Future climate conditions in the Northwest are expected to impact agriculture since there will be less water available for irrigation and increased pressure from pests, pathogens and weeds. The consequences of these impacts will differ depending on cropping systems and locations. Water availability will continue to be a major concern in the future, especially during the summer months in basins with significant reductions in mountain snowpack.
In the Northwest and beyond, climate change is expected to negatively impact human physical and mental health. Individuals and communities will be exposed to climate-related hazards such as increased rates of heat-related illnesses, respiratory illnesses, diseases, and depression and anxiety associated with environmental stressors and changes.