Pathways for Climate Change Effects on Fire: Models, Data, and Uncertainties

As the climate continues to warm, fire activity has gained importance because of the way in which it affects the biosphere and the atmosphere. Current research has focused on measuring the changing patterns in wildland fire activity, mainly area burned and fire frequency, with less emphasis on understanding the factors responsible for these changing patterns. To understand these factors, research must observe fire history records but incorporate changes in vegetation and changes in human activities alongside history records (Hessl et al. 2011). –Loren Stutts

Hessl, A. E., 2011. Pathways for Climate Change Effects on Fire: Model, Data, and Uncertainties. Progress in Physical Geography vol. 35, 393-407, doi: 10.1177/0309133311407654.

The Intergovernmental Panel on Climate Change predicts that in areas where drought is persistent, fire intensity and frequency will increase. These predictions are supported by many modeling studies but few empirical studies have attempted to document changes in fire activity. To better understand the causes responsible for changes in fire activity and better project future changes in fire seasons, researchers must study a combination of fire history data, model-based studies, and empirical studies.

Because the relationship between fire and climate respond to vegetation and fuel, new models for predicting fire activity should include potential changes in vegetation and fuel structure as a result of climate change. Using empirical evidence to support climate change impact on fire season is often difficult because of the long term, consistent records of fire occurrence needed to detect change. Tree rings, sedimentary charcoal, and soil charcoal are the three fire history methods used to predict fire regimes and to understand the relationship between fire and climate.

After reviewing empirical, model, and fire history studies, the author suggests three pathways in which fire seasons respond to climate change: changes in fuel condition, fuel volume, and ignitions. Fuel condition refers to the moisture or aridity of grasslands, woodlands, or shrubland, while fuel volume refers to changes in density of plants, trees, and shrubs as a result of drier or wetter conditions, while ignitions refer to the ability of fuels to be ignited by lightening or other natural causes and/or by humans.

Because empirical and model-based studies should better define human impact on fuel volume, ignitions and density, the author proposes that research use hindcasting or models of vegetation and fire during past climates to help justify model projections of fire activity. This would improve fire climate models through its applicability across land-use histories and types of vegetation. To further understand the interactions between climate change and human activities, research must include fire history records from areas with varied land use. Projections of fire activity should address the complexity of changing human activities, vegetation, and climate.

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