Ecological and economic assessment of prescribed burning impacts in semi-arid pastoral lands of northern Australia

Pastoral managers in savannas face difficult decisions about trading off short-term use of grass biomass for animal production against its longer termuse as fuel to manage tree - grass balances with fire. This study develops a model to represent the interactions between seasonal variability, fire behaviour, tree response, pasture growth and condition, grazing utilisation and animal productivity in a grazed savanna ecosystem. It successfully integrates simplified versions of several existing models, results of local research and expert knowledge to permit economic evaluation of tradeoffs given various fire treatments. The modelling framework also enabled the effects of wildfire events to be simulated and allowed fire and livestock management costs and revenue to be quantified. Applied to one site and climate sequence, the initial results assuming constant stocking rates show the importance of burning for the long-term maintenance of productivity, and suggest that some level of late dry season fire is needed for this. Net present values of applying different fire regimes over different time horizons emphasise the factors that pastoralists must take into account in making decisions about preferred fire regimes.