Climate change vulnerability and adaptation in southwest Washington

Abstract

Hudec, Jessica L.; Halofsky, Jessica E.; Peterson, David L.; Ho, Joanne J., eds. 2019. Climate change vulnerability and adaptation in southwest Washington. Gen. Tech. Rep. PNW-GTR-977. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 249 p. The Southwest Washington Adaptation Partnership (SWAP) was developed to identify climate change issues relevant for resource management in southwest Washington, specifically on Gifford Pinchot National Forest. This science-management partnership assessed the vulnerability of natural resources to climate change and developed adaptation options that minimize negative impacts of climate change on resources of concern and facilitate transition of diverse ecosystems to a warmer climate. The vulnerability assessment focuses on fish and aquatic habitat, vegetation, special habitats, recreation, and ecosystem services. Projected changes in climate and hydrology will have far-reaching effects on aquatic and terrestrial ecosystems, especially as frequency of extreme climatic events (drought, low snowpack) and ecological disturbances (flooding, wildfire, insect outbreaks) increases. Distribution and abundance of coldwater fish species are expected to decrease in response to higher water temperature, although effects will differ as a function of local habitat and competition with nonnative fish. Higher air temperature, through its influence on soil moisture, is expected to cause gradual changes in the distribution and abundance of plant species, with drought-tolerant species becoming more dominant. Increased frequency and extent of wildfire will facilitate vegetation change, in some cases leading to altered structure and function of ecosystems (e.g., more forest area in younger age classes). Special habitats such as riparian areas and wetlands are expected to be particularly sensitive to altered soil moisture, especially as drought frequency increases. Warmer temperatures are expected to create more opportunities for warmweather recreation activities (e.g., hiking, camping) and fewer opportunities for snow-based activities (e.g., skiing, snowmobiling). Recreationists modify their activities according to current conditions, but recreation management by federal agencies has generally not been so flexible. Timber supply and carbon sequestration may be affected by increasing frequency and extent of disturbances. Native pollinators may be affected by altered vegetation distribution and phenological mismatches between insects and plants. Resource managers convened at a SWAP workshop and developed adaptation options in response to the vulnerabilities identified in each resource area, including both high-level strategies and on-the-ground tactics. Many adaptation options are intended to increase the resilience of terrestrial and aquatic ecosystems, and to reduce the effects of existing stressors (e.g., removal of nonnative species). In terrestrial systems, a dominant theme of adaptation in southwest Washington is to accelerate restoration, particularly in drier forest types, to reduce the undesirable effects of extreme events and high-severity disturbances (wildfire, insects). In aquatic systems, a dominant theme is to restore the structure and function of streams to retain cold water for fish and other aquatic organisms. Many existing management practices are already “climate-informed” or require minor adjustment to make them so. Long-term monitoring is needed to detect climate change effects on natural resources of concern and to evaluate the effectiveness of adaptation options that are implemented.