Evidence for climate change has already been reported in thousands of publications, in locations thoroughly distributed around the globe. Variations in temperature and water availability, and extremes in weather and other disturbances continuously influence every component of ecosystems, either subtly or disastrously. The degree of environmental change effects and the ecosystem response will differ from place to place: each ecosystem will experience site-specific changes in temperature, precipitation, humidity and their timing within each year. These climatic changes and their effects on disturbance regimes, hydrologic dynamics, and biological systems will require site-specific management prescriptions to mitigate the impacts of change.
We face many uncertainties in forecasting future climate, given the natural variability of the Earth’s climate, and decisions yet to be made by the global society with regard to resource consumption, greenhouse gas production, and climate change mitigation actions. However, absent a significant change in these components, all global circulation models (GCMs) predict unprecedented increases in temperature for the western US. For example, in Washington and Oregon, air temperature is projected to increase 2.5 - 6.8°C (5 - 12°F) by late 2100 (RCP8.5). This is an astonishing amount of change for both natural and human systems that are in place. There is less agreement among the GCMs on how precipitation will change in the future. What we do know is that because winters will be warmer, more precipitation will fall as rain than we are accustomed to, the snowpack will be smaller and melt earlier in the spring, and the summers will be hotter, which will reduce the effectiveness of the precipitation that we do receive, as more is evaporated to warmer air. One of WWETAC’s greatest challenges and highest priorities continues to be translating forecasted climatic conditions into potential effects on western wildland ecosystems, and the cascading effects on humans and natural resource availability.
WWETAC has supported the continued refinement and application of a model called MC2, which simulates the mechanisms of vegetation response to climate change. MC2 belongs to a class of simulation models called dynamic global vegetation models (DGVM), which are actively developed and advanced by scientists around the world. DGVMs are specifically focused on capturing and understanding vegetation response to medium- and long-term climate change. The US Forest Service has supported DGVM development for decades to help formulate a vision into the future for management of long-lived species (trees!). MC2 can be customized for a particular region using site-specific information, and used to create projections of vegetation change under future climate scenarios. For example, MC2 simulates the mixed conifer forest in central Oregon and the montane of California, an assemblage of western yellow pine, white fir, sugar pine, and lodgepole pine, with additional canopy species. MC2 simulates how the trees and grasses in this type of forest grow under historical climate, competing for light and water, and how the competitive balance may shift as the climate changes. MC2 predicts the distributions of different types of forests, interactions with wildfire, and the resulting effects on carbon stocks and water runoff. MC2 simulations have been used in crafting management plans for multiple forests in the West, and constitutes an important tool for long-term planning.
Biophysical and socioeconomic vulnerabilities to climate change has been assessed in Alaska (Region 10), Washington and Oregon (Region 6), and in southern California (Region 5). In southeastern Alaska, the effects of climate change, isostatic rebound, and tectonic uplift on tribal near-shore resources was assessed. The effects of these components of change were considered within the context of other stressors (oil spill residual, native and exotic species invasion). This project was chosen by Region 10 as the highest priority project this year. The vulnerability of the Pacific Northwest natural resources to climate change was assessed using current and future projections of vegetation, standing biomass (timber), water resources, recreation, as well as economic indicators for community capacity to respond to environmental threats. The vulnerability of the southern four National Forests in southern California (in progress) to climate change was approached in a similar way to that of the Pacific Northwest, except different ecosystem services were evaluated: water resource, wildfire impacts, biodiversity, and recreation.
WWETAC continues to update TACCIMO, an online, advanced, annotated bibliographic service for incorporating climate change into Forest Plans for the western 18 states. Data layers supporting this tool (TRM) continue to be assessed and added when appropriate.