The overarching objective of the Western Mountain Initiative (WMI) is to understand and predict the responses of Western mountain ecosystems to climatic variability and change, emphasizing sensitivities, thresholds, and resilience.
The rate and magnitude of ecosystem responses to changes in the global atmospheric environment are variable and uncertain, ranging from gradual to abrupt, from moderate to profound. The least understood and least predictable responses are important to policy makers and land managers: those responses that are both abrupt and profound. Recent examples of such responses include ongoing drought-induced forest mortality on millions of acres in New Mexico, Arizona, and southern California, large wildfires of unprecendented severity in the western United States, extensive tree mortality from outbreaks of bark beetles, and degraded water quality in mountain lakes and streams. In each case, ecosystem thresholds were crossed relatively quickly, leading to large and often unexpected changes that will have long-term consequences for ecosystem structure, function, and production of goods and services.
The WMI team explores the effects of climate change on ecological disturbance, responses of forest vegetation, mountain hydrology, and the coupled hydro-ecological responses that determine vulnerability of Western mountain ecosystems to change. Extensive data sets, empirical studies, and monitoring programs are linked via models to quantify the effects of changing climate on forest dynamics, distribution, and productivity; fire regimes and insect outbreaks; recovery of vegetation after disturbance; hydrologic changes and glacier dynamics; and the consequences of an altered water cycle for terrestrial and aquatic ecosystems and chemistry.
Mountain ecosystems of the western United States are ideally suited to address ecological questions associated with climate change. First, they have (1) compressed climatic and biogeographic zones containing many ecosystems within relatively small areas, (2) rich paleoecological resources, which record past environmental changes and consequent ecosystem responses, and (3) common ecological drivers, such as snowpack, facilitating comparisons across ecosystems. Second, because national parks and wildernesses of the montane West have experienced minimal human disturbance, effects of environmental changes on ecosystems can be inferred with fewer confounding influences than on intensively managed lands. Third, Western mountain ecosystems are important to society, providing water, wood products, carbon sequestration, biodiversity, and recreational and spiritual opportunities. Finally, more than two decades of USGS research at five Western mountain parks provides the foundation for broad syntheses of existing knowledge.
Our current research priorities are forest vegetation and disturbance, mountain hydrology, and ecohydrology, with the goals of 1) determining the vulnerability (i.e. rapidity and magnitude of change) of forest and hydrologic processes to climate-induced changes, and 2) developing methodologies for adaptation that are tailored to watershed- and regional-scale issues. Ongoing WMI research tasks include:
- Cross-site comparisons of forest dynamics across 7 Western states, and projecting forest changes into the future.
- Quantify variability in fire severity among mountain ecosystems in response to climate change, particularly the duration and intensity of summer drought and extreme weather.
- Identify how climate-based stresses on trees and climate effects on insect populations combine to affect insect outbreaks and forest mortality.
- Quantify effects of fires and insect outbreaks on forest carbon dynamics in the western states, and project future forest carbon sequestration.
- Analyze trends in timing and magnitude of snowpack accumulation and ablation and mountain hydrology for five national parks, and project future trends.
- Develop mass balances for glacier bodies across the conterminous US, and forecast rates of glacier recession.
- Survey changes in water quality from glacier and cryospheric wasting, and produce maps and forecasts of the risks to water quality and aquatic ecosystems from heavy metals and nutrients in the western US.
These tasks will inform two broad goals for synthesis and application:
- Synthesize empirical and modeled results to infer mountain ecosystem resilience to climate change.
- Work closely with National Park Service and US Forest Service (USFS) managers to craft and implement site-specific adaptations.
WMI addresses each of the goals and objectives of the USGS Climate and Land Use Change Research and Development (CLU R&D). WMI focuses on sensitivities and response thresholds of resources to climatic stressors (Goals 1.1, 1.3) and identification of critical areas (Goal 1.2). Causal mechanisms driving ecosystem responses to climatic variability (Goal 2) are addressed by regional expansion, modeling, and continued monitoring across five mountain regions. Spatial scaling (plot to sub-continent) and temporal scaling (daily to millennial) are strong features of WMI and address Goals 3.1-3.4. Carbon sequestration and flux (Goal 5) in mountain regions are evaluated through modeling and field studies and will likely be a future strategic DOI concern (Goal 5.6). We incorporate federal land managers through formal (e.g. workshops) and informal avenues to test management relevance of research products (Goal 4).