Models of emissions from savannas Garry Cook, Mick Meyer, Damian Barrett, Ian Galbally, Dean Graetz, Kevin Tolhurst, Jeremy Russell-Smith CSIRO Sustainable Ecology, CSIRO Atmospheric Research, CSIRO Plant Industry, CSIRO Earth Observation Centre, Faculty of Ag & Forestry, Melbourne University, Bushfires Council of the Northern Territory Models can help us quickly understand how complex issues may affect us. This talk will focus on a model we have recently developed to understand how fire regimes affect vegetation and smoke emissions.

Talk outline Overview of savannas The ecosystem, the emissions Uncertainties in emissions Fuel combustion Errors of omission and commission Towards full accounting Questions of fire regime Supporting a land management industry

Characteristics of tropical savannas C. 1/3 of world’s land surface Wet / dry tropics Trees and grass Variable fuel load Frequent fires Size, timing, intensity, EF,

Savanna biomass burning emissions (Andreae & Merlet 2001) Savannas World % Fuel consumed 3160 8600 37 CO2 5096 13400 38 CO 206 690 30 CH4 7.4 39 19

Australian National Inventory estimates of GHG emissions from savanna fires in 1999 Species Emission Gg Emission Gg CO2-e % National emission CH4 361 7600 6 N2O 18.5 5743 19 NOx 1070 - 40 CO 14115 63 VOC 825 39

How well do we know the savanna fire emissions? Species Range (Gg) Mean (Gg) CV (%) CH4 135 – 816 369 49.8 N2O 6.1 - 43.4 18.8 54.0 NOx 341 - 2583 1091 53.9 CO 5139 – 31844 14419 50.6 VOC 303 - 1850 839 Not very well!

Algorithm Fuelburned = scar area x fuelload x fracb Ei = Fuelburned x effic b x CCi x EFi fractb fraction of scar area which burns efficb combustion efficiency Ei emission of species i CCi Carbon content EFi Emission factor of species i

Which factors are most uncertain?

The value of improved fuel estimates Southern Africa (Scholes et al.) 90-264 Tg fuel model 247-2719 Tg conventional classification West Africa (Menaut et al.) 50% with improved fuels estimate

Fine: grass, tree litter The fate of burnt fuel Emissions 73 - 85% mass Entrained char 6-18% mass Fuel Fine: grass, tree litter Coarse: logs, branches Deposited char 9% mass

Fine fuel dynamics Time since fire Amount Composition Quality Fires C/N EF Flaming Smoldering Fire frequency is how often fires occur. In much of the Top End fire occur in any given area in more than 4 years out of 10. The time between fires is critical. Does it allow saplings to grow beyond a fire sensitive size? Does it allow plants that reproduce only by seed to have matured and flowered? Do fuel loads accumulate to the degree that a later fire will have extremely high intensities?

Spatial and temporal heterogeneity Proportion burnt In areas with a flame Patchiness Landscape and timing

Fine vs Coarse fuel Tree (or shrub) / grass ratio Fine fuel in savannas Potentially > 50 % fine tree litter Fine / coarse fuel Flaming / smoldering 30% underestimate of total fuel? Variation across ecosystems? 69% Flaming

Net effects of fires on C stocks? Fire regimes have changed Australian pre 1900 smaller patchy fires all fire season Grazing lands: current Infrequent, early or v. late Other lands: current frequent, late How to account for changing woody biomass?

Area burnt Calibration of NOAA to Landsat

Area burnt Calibration of NOAA to Landsat Landsat > NOAA Early, small, low intensity

Area burnt Calibration of NOAA to Landsat Landsat > NOAA Early, small, low intensity Landsat < NOAA Large but patchy fires

Area burnt Calibration of NOAA to Landsat Landsat > NOAA Early, small, low intensity Landsat < NOAA Large but patchy fires Landsat ~ NOAA 1 : 1

Towards full accounting The questions of fire regime All land is managed land Total emissions budget Fire Decomposition Herbivory Sequestration Charcoal Growth

Fire regimes Frequency Fuel loads, composition, cumulative impacts Timing Intensity Impacts on trees Spatial heterogeneity Burnt / unburnt matrix Variation in intensity Dynamics in absence of fire

Savanna burning vs termite emissions (Andreae & Merlet 2001; Khalil et al. 1990) (Tg/y) Termites Fuel consumed 3160 7000 CO2 5096 4000 CO 206 CH4 7.4 12

ALFA Project

Products Supporting a carbon trading industry? Links to dynamic fuel load and emissions maps Links to maps of trends in carbon stocks Time since fire maps Fire spread maps Direct estimates of emissions

Increasing the spatial and temporal detail Satellite-based fire scar information Fuel loads from ecological production models Seasonality information (could refine estimates of burning efficiency and emission factors)