Carbon dioxide and particulate emissions from the 2013 Tasmanian firestorm: implications for Australian carbon accounting

Background Uncontrolled wildfires in Australian temperate Eucalyptus forests produce significant smoke emissions, particularly carbon dioxide (CO2) and particulates. Emissions from fires in these ecosystems, however, have received less research attention than the fires in North American conifer forests or frequently burned Australian tropical savannas. Here, we use the 2013 Forcett-Dunalley fire that caused the first recorded pyrocumulonimbus event in Tasmania, to understand CO2 and particulate matter (PM2.5) emissions from a severe Eucalyptus forest fire. We investigate the spatial patterns of the two emissions using a fine scale mapping of vegetation and fire severity (50 m resolution), and utilising available emission factors suitable for Australian vegetation types. We compare the results with coarse-scale (28 km resolution) emissions estimates from Global Fire Emissions Database (GFED) to determine the reliability of the global model in emissions estimation. Results The fine scale inventory yielded total CO2 emission of 1.125 +/- 0.232 Tg and PM2.5 emission of 0.022 +/- 0.006 Tg, representing a loss of 56 t CO2 ha(-1) and 1 t PM2.5 ha(-1). The CO2 emissions were comparable to GFED estimates, but GFED PM2.5 estimates were lower by a factor of three. This study highlights the reliability of GFED for CO2 but not PM2.5 for estimating emissions from Eucalyptus forest fires. Our fine scale and GFED estimates showed that the Forcett-Dunalley fire produced 30% of 2013 fire carbon emissions in Tasmania, and 26-36% of mean annual fire emissions for the State, representing a significant single source of emissions. Conclusions Our analyses highlight the need for improved PM2.5 emission factors specific to Australian vegetation, and better characterisation of fuel loads, particularly coarse fuel loads, to quantify wildfire particulate and greenhouse gas emissions more accurately. Current Australian carbon accountancy approach of excluding large wildfires from final GHG accounts likely exaggerates Tasmania's claim to carbon neutrality; we therefore recommend that planned and unplanned emissions are included in the final national and state greenhouse gas accounting to international conventions. Advancing these issues is important given the trajectory of more frequent large fires driven by anthropogenic climate change.

Automated summary

This study examines the CO2 and particulate matter emissions from a severe Eucalyptus forest fire in Tasmania. The results show that the emissions of CO2 are comparable to the estimates from the Global Fire Emissions Database (GFED), but the PM2.5 estimates are lower. The study highlights the need for improved PM2.5 emission factors specific to Australian vegetation and better characterization of fuel loads to accurately quantify wildfire emissions. The inclusion of planned and unplanned emissions in greenhouse gas accounting is recommended to have a more accurate assessment of carbon neutrality. The importance of addressing these issues is emphasized in light of increased large fires due to climate change.