Vulnerability and adaptation to climate change in the Blue Mountains


Halofsky, J.E. and D.L. Peterson (eds.). 2017. Vulnerability and adaptation to climate change in the Blue Mountains. USDA General Technical Report PNW-GTR-939. Pacific Northwest Research Station, Portland, OR.


The Blue Mountains Adaptation Partnership (BMAP) is a science-management partnership consisting of Malheur National Forest, Umatilla National Forest, Wallowa-Whitman National Forest, the U.S. Forest Service Pacific Northwest Research Station and Pacific Northwest Region, the University of Washington, and the Climate Impacts Research Consortium at Oregon State University. These organizations worked together over a period of two years to identify climate change issues relevant to resource management in the Blue Mountains region and to find solutions that can minimize negative effects of climate change and facilitate transition of diverse ecosystems to a warmer climate. The BMAP provided education, conducted a climate change vulnerability assessment, and developed adaptation options for federal agencies that manage 2.1 million hectares in northeast Oregon, southeast Washington, and a small portion of southwest Idaho. Global climate models project that the current warming trend will continue throughout the 21st century in the Blue Mountains. Compared to observed historical temperature, average warming is projected to be 2.4-3.1 °C by 2050 and 3.2-6.3 °C by 2100, depending on greenhouse gas emissions. Precipitation may increase slightly in the winter, although the magnitude is uncertain. The effects of climate change on hydrology in the Blue Mountains will be especially significant. Decreased snowpack and earlier snowmelt will shift the timing and magnitude of streamflow and decrease summer soil moisture; peak flows will be higher, and summer low flows will be lower. Pronounced changes in snow and streamflow will occur in headwater basins of the Wallowa Mountains, especially in high-elevation radial drainages out of the Eagle Cap Wilderness, with large changes occurring in the more northerly sections of the Umatilla and Wallowa-Whitman National Forests along the Oregon-Washington border. Mid-elevation areas where snow is currently not persistent (northern Blue Mountains, margins of Wallowa, Elkhorn, Greenhorn, and Strawberry Mountains) may become largely snow-free in the future. Projected changes in climate and hydrology will have far-reaching effects on aquatic and terrestrial ecosystems, especially as frequency of extreme climate events (drought, low snowpack) and associated effects on ecological disturbance (streamflow, wildfire, insect outbreaks) increase. Vulnerability assessment and adaptation option development for the Blue Mountains conclude the following:

Water resources and infrastructure

  • Effects: Decreasing snowpack and declining summer flows will alter timing and availability of water supply, affecting municipal and public uses downstream from and in national forests, and other forest uses including livestock, wildlife, recreation, firefighting, road maintenance, and in-stream fishery flows. Declining summer low flows will affect water availability during late summer, the period of peak demand (e.g., for irrigation and power supply). Increased magnitude of peak streamflows will damage roads near perennial streams, ranging from minor erosion to complete loss of the road prism, thus affecting public safety, access for resource management, water quality, and aquatic habitat. Bridges, campgrounds, and national forest facilities near streams and floodplains will be especially vulnerable, reducing access by the public.
  • Adaptation options: Primary adaptation strategies to address changing hydrology in the Blue Mountains include restoring the function of watersheds, connecting floodplains, reducing drainage efficiency, maximizing valley storage, and reducing fire hazard. Tactics include adding wood to streams, restoring beaver populations, modifying livestock management, and reducing surface fuels and forest stand densities. Primary strategies for infrastructure include increasing the resilience of stream crossings, culverts, and bridges to higher peak flows and facilitating response to higher peak flows by reducing the road system and disconnecting roads from streams. Tactics include completing geospatial databases of infrastructure (and drainage) components, installing higher capacity culverts, and decommissioning roads or converting them to alternative uses.


  • Effects: Decreased snowpack will shift the timing of peak flows, decrease summer low flows, and in combination with higher air temperature, increase stream temperatures, all of which will reduce the vigor of cold-water fish species. Abundance and distribution of spring Chinook salmon, redband trout/steelhead, and especially bull trout will be greatly reduced, although effects will vary by location as a function of both stream temperature and competition from non-native fish species. Increased wildfire will add sediment to streams, increase peak flows and channel scouring, and raise stream temperature by removing vegetation.
  • Adaptation options: Primary strategies to address climate change threats to cold-water fish species include maintaining or restoring natural flow regimes to buffer against future changes, decreasing fragmentation of stream networks so aquatic organisms can access similar habitats, and developing wildfire use plans that address sediment inputs and road failures. Tactics include using watershed analysis to develop integrated actions for vegetation and hydrology, protecting groundwater and springs, restoring riparian areas and beaver populations to maintain summer base flows, reconnecting and increasing off channel habitat and refugia, identifying and improving stream crossings that impede fish movement, implement engineering solutions to improve stream structure and flow, decreasing road connectivity, and revegetating burned areas to store sediment and maintain channel geomorphology.

Upland vegetation

  • Effects: Increasing air temperature, through its influence on soil moisture, is expected to cause gradual changes in the abundance and distribution of tree, shrub, and grass species throughout the Blue Mountains, with more drought tolerant species becoming more competitive. Ecological disturbance, including wildfire and insect outbreaks, will be the primary facilitator of vegetation change, and future forest landscapes may be dominated by younger age classes and smaller trees. High-elevation forest types will be especially vulnerable to disturbance. Increased abundance and distribution of non-native plant species will create additional competition for regeneration of native plant species.
  • Adaptation options: Most strategies for conserving native tree, shrub, and grassland systems focus on increasing resilience to drought, low snowpack, and ecological disturbance (wildfire, insects, non-native species). These strategies generally include managing landscapes to reduce the severity and patch size of disturbances, encouraging fire to play a more natural role, and protecting refugia. Tactics include using silvicultural prescriptions (especially stand density management) and fuel treatments to reduce fuel continuity, reducing populations of non-native species, potentially modifying seed zones for tree species, and revising grazing policies and practices. Rare and disjunct species and communities (e.g., whitebark pine, aspen, alpine communities) require adaptation strategies and tactics focused on encouraging regeneration, preventing damage from disturbance, and establishing refugia.

Special habitats

  • Effects: Riparian areas and wetlands will be especially vulnerable to higher air temperature, reduced snowpack, and altered hydrology. The primary effects will be decreased establishment, growth, and cover of species such as cottonwood, willow, and aspen, which may be displaced by upland forest species in some locations. However, species that propagate effectively following fire will be more resilient to climate change. Reduced groundwater discharge to groundwater-dependent ecosystems will reduce areas of saturated soil, convert perennial springs to ephemeral springs, eliminate some ephemeral springs, and alter local aquatic flora and fauna communities.
  • Adaptation options: Primary strategies for increasing resilience of special habitats to changing climate include maintaining appropriate densities of native species, propagating drought tolerant native species, maintaining or restoring natural flow regimes to buffer against future changes, and reducing stresses such as conifer encroachment, livestock grazing, and ungulate browsing. Tactics include planting species with a broad range of moisture tolerance, controlling non-native species, implementing engineering solutions to maintain or restore flows, restoring beaver populations, reducing damage from livestock and native ungulates, and removing infrastructure (e.g., campsites, springhouses) where appropriate.

The BMAP facilitated one of the largest climate change adaptation efforts on federal lands to date, including participants from stakeholder organizations interested in a broad range of resource issues. It achieved specific goals of national climate change strategies for the U.S. Forest Service, providing a scientific foundation for resource management, planning, and ecological restoration in the Blue Mountains region. The large number of adaptation strategies and tactics, many of which are a component of current management practice, provide a pathway for slowing the rate of deleterious change in resource conditions. Rapid implementation of adaptation in sustainable resource management will help maintain critical structure and function of terrestrial and aquatic ecosystems in the Blue Mountains. Long-term monitoring will help detect potential climate change effects on natural resources, and evaluate the effectiveness of adaptation options that have been implemented.