A New Picture of Fire Extent, Variability, and Drought Interaction in Prescribed Fire Landscapes: Insights From Florida Government Records

Abstract

Florida, United States, government records provide a new resource for studying fire in landscapes managed with prescribed fire. In Florida, most fire area (92%) is prescribed. Current satellite fire products, which underpin most air pollution emission inventories, detect only 25% of burned area, which alters airborne emissions and environmental impacts. Moreover, these satellite products can misdiagnose spatiotemporal variability of fires. Overall fire area in Florida decreases during drought conditions as prescribed fires are avoided, but satellite data do not reflect this pattern. This pattern is consistent with prescribed fire successfully reducing overall fire risk and damages. Human management of prescribed fires and fuels can, therefore, break the conventional link between drought and wildfire and play an important role in mitigating rising fire risk in a changing climate. These results likely apply in other regions of the world with similar fire regimes.

Keywords: biomass burning; climate; prescribed fire; remote sensing; wildfire.

Figure 1

Mean annual burned area in Florida during 2004–2015 for (a) four fire types reported by FFS OBA (this work) and FPA FOD (Short, 2017), (b) total fires compared to satellite products (GFED version 4.1s and Landsat BAECV version 1.1; van der Werf et al., 2017; Hawbaker et al., 2017a), and (c) the ratio of reported to detected fire area. Panel a uses 0.1° resolution; panel b uses the 0.25° GFED grid to aid comparisons. Note the change in color scale at 5%. Lines are major highways and dots represent major cities. Panel c shows the ratios for each grid cell in Florida. The black line and shading show the mean ratio, weighted by fire area, and its 95% confidence interval (Text S5). FFS OBA = Florida Forest Service open burn authorization; FPA PPOD = Fire Program Analysis Fire Occurrence Database; GFED = Global Fire Emissions Database; BAECV = Burned Area Essential Climate Variable.

Figure 2

Fire area in Florida (a) by day of week, (b) by seasonal cycle, (c) monthly over the study period, and (d) monthly anomalies, with (e) drought indices for comparison. Prescribed fire data from Florida Forest Service (this work), wildfire data from Fire Program Analysis Fire Occurrence Database (Short, 2017), and Global Fire Emissions Database (GFED) from version 4.1s (van der Werf et al., 2017). Vertical lines in panels a and b show standard errors of the mean, which is smaller than some plot symbols. Anomalies in panel d are calculated with respect to the median annual cycle, shown in panel b, and smoothed with a 3‐month running mean. Drought indices are the Palmer drought severity index (PDSI) and Keetch‐Byram drought index (KBDI), both averaged over Florida. Dry conditions are associated with negative PDSI and large positive KBDI. The PDSI axis is reversed so that up indicates drought for both KBDI and PDSI.