Project Funding: 2014 - 2017

NRA: 2013 NASA: Terrestrial Ecology   

Funded by NASA

Abstract:
Invasive grasses are increasing fire activity globally, yet the mechanisms driving the initiation and perpetuation of these novel fire regimes remain largely unknown. Our proposed work will compare how short-term climate, long-term climate and land use interact with land cover across the intermountain west to alter the probability and behavior of fires. Climate interactions with wildfires in forested lands of the western U.S. are well studied, with forest fires generally promoted by short-term drought and warmer temperatures which lead to fuel desiccation and increased flammability. Fires in arid ecosystems dominated by invasive cheatgrass (Bromus tectorum) are thought to be largely driven by long-term moisture availability, which increases fuel biomass and cover. However, at a regional scale, this association has not been empirically tested despite ongoing concern about cheatgrass fires, which we have shown to be larger, faster spreading and more frequent than fires in native land cover. Current predictive models of fire risk, based on climatic conditions that drive forest fires, are insufficient for predicting fires in the intermountain west because they neglect both the presence of cheatgrass and the unique climatic and land use conditions that influence cheatgrass fires. This research will address: How do climate and land use influence fire likelihood and behavior in native and invaded ecosystems across the intermountain west? Using novel techniques that we have developed to detect cheatgrass and derive fire regime metrics from remote sensing data, we will explore this major question. We hypothesize that cheatgrass fires will be related primarily to coupled extreme wet-dry climate conditions and strongly associated with human ignitions, compared with native forest fires. Burn probability and fire behavior will be derived from the MODIS burned area and active fire products. Regional meteorological and land use maps will be used to assess climate and land use. A regional, updated map of cheatgrass will be created from MODIS time series to differentiate invaded land cover. Using these spatial layers, we will develop an integrated model framework that predicts burn probability and fire behavior based on short-term climate, long-term climate, land cover, and proximity to land use. This analysis will: i) assess fire dynamics in the intermountain west in relation to preceding climate conditions and proximity to anthropogenic ignition sources; and ii) model current and mid-century fire risk in ecosystems and developed areas across the western U.S under future climate change and land use scenarios. A predictive framework for understanding how climate and land use interact with land cover to promote fires will improve assessments of vulnerability of intermountain west terrestrial ecosystems to global and regional environmental change. We will integrate Earth observations from satellites into statistical models to create spatial predictions of wildfire vulnerability. These analyses are critically needed given that cheatgrass doubles the likelihood of fire and played a prominent role in the largest fire events in the intermountain west during the last decade. Assessing the relative influence of climate and anthropogenic drivers will also provide insights into how the cheatgrass-fire cycle can be prevented or reversed. While climate-induced shifts in fire activity have already been observed and predicted in forest ecosystems, little is known about how invasive grass fuels will concurrently change fire activity on regional to global scales. Our study will provide new mechanistic insights and foundational methods to characterize and quantify the current and future influence of feedbacks between climate, land use, and invasive grasses on native fire regimes.

Publications:

Abatzoglou, J. T., Balch, J. K., Bradley, B. A., Kolden, C. A. 2018. Human-related ignitions concurrent with high winds promote large wildfires across the USA. International Journal of Wildland Fire. 27(6), 377. DOI: 10.1071/WF17149

Abatzoglou, J. T., Kolden, C. A., Balch, J. K., Bradley, B. A. 2016. Controls on interannual variability in lightning-caused fire activity in the western US. Environmental Research Letters. 11(4), 045005. DOI: 10.1088/1748-9326/11/4/045005

Abatzoglou, J. T., Williams, A. P. 2016. Impact of anthropogenic climate change on wildfire across western US forests. Proceedings of the National Academy of Sciences. 113(42), 11770-11775. DOI: 10.1073/pnas.1607171113

Balch, J. K., Bradley, B. A., Abatzoglou, J. T., Nagy, R. C., Fusco, E. J., Mahood, A. L. 2017. Human-started wildfires expand the fire niche across the United States. Proceedings of the National Academy of Sciences. 114(11), 2946-2951. DOI: 10.1073/pnas.1617394114

Fusco, E. J., Abatzoglou, J. T., Balch, J. K., Finn, J. T., Bradley, B. A. 2016. Quantifying the human influence on fire ignition across the western USA. Ecological Applications. 26(8), 2390-2401. DOI: 10.1002/eap.1395

Williams, A. P., Abatzoglou, J. T. 2016. Recent Advances and Remaining Uncertainties in Resolving Past and Future Climate Effects on Global Fire Activity. Current Climate Change Reports. 2(1), 1-14. DOI: 10.1007/s40641-016-0031-0

2015 NASA Carbon Cycle & Ecosystems Joint Science Workshop Poster(s)

• Introduced annual grass increases regional fire activity across the arid western USA (1980–2009)   --   (Jennifer Balch, Bethany Bradley, Carla D'Antonio, Jose Gomez-Dans)   [abstract]
• Lightning Ignited Fires over the Western United States   --   (John Abatzoglou, Bethany Bradley, Emily Fusco, Jennifer Balch)   [abstract]
• Quantifying human influence on fire ignitions across the western U.S.   --   (Emily Fusco, John Abatzoglou, Jennifer Balch, Bethany Bradley)   [abstract]

More details may be found in the following project profile(s):

• NASA Terrestrial Ecology (TE) Project Profile