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Climate Change


The United States Department of Defense (DoD) recognizes growing climate risks across its responsibilities as land manager, operator of hundreds of installations, and in its core mission to protect national security. However, DoD climate risk reduction is complicated by frequent leadership turnover among base commanders, which encourages focus on near-term challenges, and changing US government priorities that downplay climate risk.
Wildland research, management, and policy in western democracies have long relied on concepts of equilibrium: succession, sustained yield, stable age or species compositions, fire return intervals, and historical range of variability critically depend on equilibrium assumptions. Not surprisingly, these largely static concepts form the basis for societal expectations, dominant management paradigms, and environmental legislation.
Warming‐induced mountain pine beetle (Dendroctonus ponderosae; MPB) outbreaks have caused extensive mortality of whitebark pine (Pinus albicaulis; WBP) throughout the species’ range. In the highest mountains where WBP occur, they cross alpine treeline ecotones (ATEs) where growth forms transition from trees to shrub‐like krummholz, some of which survived recent MPB outbreaks.
Allometric equations are widely used to estimate forest aboveground biomass (AGB). However, their development rarely includes the oldest and largest trees, leading to estimation errors. Black locust (Robinia pseudoacacia) is an early successional nitrogen-fixing tree, native to the Eastern United States.
Average annual temperature over the contiguous United States has increased by 0.7 degrees Celsius (°C; 1.2 degrees Fahrenheit (°F) for the period 1986-2016 compared to 1901-1960 (Vose and others, 2017). Warming temperatures, increased frequency of heat waves, and possibly drought have likely contributed to longer fire seasons, more extreme fire weather, and consequently, larger amounts of sagebrush (Artemisia spp.) burned each year.
Coarse woody debris (CWD) is an important component in forests, hosting a variety of organisms that have critical roles in nutrient cycling and carbon (C) storage. We developed a process-based model using literature, field observations, and expert knowledge to assess woody debris decomposition in forests and the movement of wood C into the soil and atmosphere.
Global change has resulted in chronic shifts in fire regimes. Variability in the sensitivity of tree communities to multi-decadal changes in fire regimes is critical to anticipating shifts in ecosystem structure and function, yet remains poorly understood.
Brown root rot (caused by Phellinus noxius) and myrtle rust (caused by Austropuccinia psidii) are natural disturbances in their native tropical and subtropical forest ecosystems. A tree infected with either fungal pathogen becomes unhealthy and likely dies, sometimes within 3 months.
Over the last century in the circumpolar north, notable terrestrial ecosystem changes include shrub expansion and an intensifying wildfire regime. Shrub invasion into tundra may be further accelerated by wildfire disturbance, which creates opportunities for establishment where recruitment is otherwise rare. The Seward Peninsula currently experiences more frequent and larger fires than other tundra regions in Alaska.
Mean surface temperatures have increased globally by ~0.7 °C per century since 1900 and 0.16 °C per decade since 1970 (Levinson and Fettig 2014). Most of this warming is believed to result from increases in atmospheric concentrations of greenhouse gases produced by human activity.