An international team of researchers led by Pacific Northwest National Laboratory working at the Joint Global Change Research Institute developed a new model on vegetation fires that will improve understanding of such fires around the world today. It can also predict their evolution with future changes in the environment and society. As reported in Biogeosciences, HESFIRE (Human-Earth System FIRE) integrates the role of atmospheric changes like humidity, terrestrial factors like the amount of vegetation available to burn, and human interactions with the environment.
“The model builds on previous research but adds new features not previously considered,” says Dr. Yannick Le Page, a PNNL forestry scientist, who led the team. “It includes how fire spreads over consecutive days and realistically represents fire incidence across regions as well as extreme events.”
Scientists at PNNL's Joint Global Climate Change Research Institute (JGCRI), NASA, the University of Lisbon, and the University of Maryland designed the HESFIRE model around three areas:
Fire ignition—how fires start, including weather-related factors such as lightning strikes and human-related factors such as agriculture, ecosystem management, and other land use practices.
Fire spread—how fires grow based on weather conditions such as relative humidity, temperature, and wind speed, and vegetation conditions such as soil moisture and the kinds of plants available (forest, shrub, or grass)
Fire termination—what controls the way fires burn out, whether from natural causes such as weather conditions and fuel availability or human factors such as changes in the landscape and fire suppression efforts.
The research team then evaluated the model using satellite data from fires around the world to ensure HESFIRE correctly matched real-world results. Their evaluation highlighted the strengths of the model and also identified some areas for improvement.
Forest and grassland fires can change the landscape, affecting biodiversity, farming, and even climate. These vegetation fires spew greenhouse gasses and particles into the atmosphere, adding their contribution to those of industrial pollutants and the burning of fossil fuels. Being able to predict where fire activity might change is key to anticipating how that activity might impact the environmental and society. But the cause of fires is a complex web of weather, nature, timing, and human factors that is very difficult to untangle.
The new model will allow scientists to explore potential fire trends under future conditions, identify hotspots particularly susceptible to changes in climate and human activities, and integrate results with other models tracking air quality and biodiversity.
Humans exert considerable influence over global fire activity. Fire-driven deforestation accounts for an estimated 20% of the increase in atmospheric CO2 from human activities since preindustrial times. Fire activity depends on a range of drivers covering three major components of the human-Earth system: the atmosphere (e.g., weather conditions), the terrestrial biosphere (e.g., fuel loads), and anthropogenic activities (e.g., land-use fires and fire suppression). The interaction among these drivers determines global fire patterns. Modeling fire activity under future climate, policy, and land-use scenarios requires a framework with a broad range of variables and a good understanding of the influence of these variables for model parameterization. A team of scientists, led by a U.S. Department of Energy researcher at Pacific Northwest National Laboratory, developed a new fire model called Human-Earth System FIRE (HESFIRE), which integrates the influence of weather, vegetation characteristics, and human activities on fire. The team found the modeled fire activity showed reasonable agreement with observations of burned area, fire seasonality, and inter-annual variability in many regions, including for spatial and temporal domains not included in the optimization procedure. The characteristics of HESFIRE and the outcome of its evaluation provide insights into the influence of anthropogenic activities and weather, and their interactions, on fire activity. The integration of HESFIRE into a dynamic global vegetation model (DGVM) could also provide insights into the contribution of fire-driving assumptions, observation data, and DGVM-derived vegetation/fuel characteristics to model performances.
The authors are grateful for research support provided by the NASA Terrestrial Ecology and Inter-Disciplinary Studies programs. The authors also wish to express appreciation to the Integrated Assessment Research Program in the Office of Science of the U.S. Department of Energy for partially funding this research. The Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute under contract DE-AC05-76RL01830. The views and opinions expressed in this paper are those of the authors alone.