Mid‐21st‐century climate changes increase predicted fire occurrence and fire season length, Northern Rocky Mountains, United States

Abstract

Abstract. Climate changes are expected to increase fire frequency, fire season length, and cumulative area burned in the western United States. We focus on the potential impact of mid-21st-century climate changes on annual burn probability, fire season length, and large fire characteristics including number and size for a study area in the Northern Rocky Mountains. Although large fires are rare they account for most of the area burned in western North America, burn under extreme weather conditions, and exhibit behaviors that preclude methods of direct control. Allocation of resources, development of management plans, and assessment of fire effects on ecosystems all require an understanding of when and where fires are likely to burn, particularly under altered climate regimes that may increase large fire occurrence. We used the large fire simulation model FSim to model ignition, growth, and containment of wildfires under two climate scenarios: contemporary (based on instrumental weather) and mid-century (based on an ensemble average of global climate models driven by the A1B SRES emissions scenario). Modeled changes in fire patterns include increased annual burn probability, particularly in areas of the study region with relatively short contemporary fire return intervals; increased individual fire size and annual area burned; and fewer years without large fires. High fire danger days, represented by threshold values of Energy Release Component (ERC), are projected to increase in number, especially in spring and fall, lengthening the climatic fire season. For fire managers, ERC is an indicator of fire intensity potential and fire economics, with higher ERC thresholds often associated with larger, more expensive fires. Longer periods of elevated ERC may significantly increase the cost and complexity of fire management activities, requiring new strategies to maintain desired ecological conditions and limit fire risk. Increased fire activity (within the historical range of frequency and severity, and depending on the extent to which ecosystems are adapted) may maintain or restore ecosystem functionality; however, in areas that are highly departed from historical fire regimes or where there is disequilibrium between climate and vegetation, ecosystems may be rapidly and persistently altered by wildfires, especially those that burn under extreme conditions.

Modeling Fuel Treatment Leverage: Encounter Rates, Risk Reduction, and Suppression Cost Impacts

“…Changes in climate resulting in warmer, drier conditions along with extended fire season lengths suggest a future of increasing fire activity [1][2][3]. The joint impacts of population growth and expanded ex-urban development will likely result in more human-caused ignitions along with more homes and communities exposed to fire [4][5][6][7][8][9].…”

Prediction of Forest Canopy and Surface Fuels from Lidar and Satellite Time Series Data in a Bark Beetle-Affected Forest

“…Forest disturbance has increased in recent years, and is projected to continue to increase in coming decades, in part due to climate change [4][5][6][7][8]. Many aspects of wildfire behavior and effects are greatly influenced by forest fuels [9,10], which are shaped by prior disturbances such as insect epidemics, drought, fire, and disease.…”

A Model-Based Framework to Evaluate Alternative Wildfire Suppression Strategies

“…We chose the Large Fire Simulator (FSim) as it has these capabilities [64]. FSim has been widely used in hazard and risk assessments [3,30,65,66]. FSim was designed to simulate the ignition and growth of fires under weather conditions during which fires grow large, as these fires contribute the vast majority of burned area under current fire suppression strategies [64].…”

“…Wildland fire management in the United States and elsewhere has increased in complexity commensurate with dramatic shifts in the fire environment due to factors such as changing climate, land use and population [1][2][3][4]. These shifts produce continued if not growing concerns over escalating fire suppression costs, losses of highly valued resources including homes, and firefighter fatalities (e.g., [5,6]).…”