Managing fire regimes in north Australia J Russell-Smith et al. ). Conversely, very limited burning is typically undertaken in more fertile, productive settings, despite the potential for applying relatively intense fires to combat encroachment by woody vegetation in some pastoral regions (Williams et al. 2002).Much of the frequently fire-affected land is under Aboriginal ownership -either under freehold title or, increasingly, under non-exclusive title arrangements (known as "native title"), as part of recent formal Australian State and Territory Government recognition of prior Aboriginal custodianship. Outside of urban settlements, Aboriginal people constitute the majority of the rural population in remote north Australian territories and, despite being "land rich", they remain severely economically and socially disadvantaged (RussellSmith et al. 2009b; White-head et al. 2009).Fires are deliberately ignited for a variety of traditional Aboriginal and other landmanagement purposes; lightning ignitions are confined to the onset of the stormy monsoonal season, typically between October and December (Russell-Smith et al. 2007). Minimal infrastructure combined with a very sparsely settled rural population (< 0.1 person per km 2 ) has resulted in a limited capacity to manage escaped fires; fire regimes in many regional settings are therefore characterized by the frequent (annual-biennial) recurrence of large (> 1000 km 2 ), late dryseason wildfires. Despite the appearance that relatively unmodified north Australian, eucalypt-dominated savanna systems are structurally intact and healthy, contemporary fire regimes are increasingly recognized as having drastic regional impacts on sustainable land use (Russell-Smith et al. 2003b), biodiversity (Woinarski et al. 2011;Russell-Smith et al. 2012), and GHG emissions and C storage (Murphy et al. 2010;Williams et al. 2012). The development of these contemporary burning patterns follows a breakdown in traditional Aboriginal methods of fire management, associated with societal collapse dating from the late 19th century (Ritchie 2009;. Traditionally, burning was undertaken throughout the year over much of northern Australia, with a focus on implementing extensive "cleaning of country" management through intensive application of small patchy burns in the early-mid dry season (Russell-Smith et al. 2003b). In Aboriginal-owned West Arnhem Land, for 2010). Typically, accountable GHG emissions contribute between 2-4% of Australia's annual National Greenhouse Gas Inventory (NGGI; ANGA 2011a). In accordance with international accounting rules, Australia's NGGI does not account for carbon dioxide (CO 2 ) emissions from savanna burning, on the assumption that such fires produce no net CO 2 flux (IPCC 1997). However, it is recognized that C fluxes in flammable savanna systems are dependent on fire regime characteristics, especially under changing fire frequency and intensity conditions (Beringer et al. 2007;Cook and Meyer 2009).In accordance with other provisions of the Kyoto Protocol, ...

Considerable research has been undertaken over the past two decades to apply remote sensing to the study of fire regimes across the savannas of northern Australia. This work has focused on two spatial scales of imagery resolution: coarse-resolution NOAA-AVHRR imagery for savanna-wide assessments both of the daily distribution of fires ('hot spots'), and cumulative mapping of burnt areas ('fire-scars') over the annual cycle; and fine-resolution Landsat imagery for undertaking detailed assessments of regional fire regimes. Importantly, substantial effort has been given to the validation of fire mapping products at both scales of resolution. At the savanna-wide scale, fire mapping activities have established that: (1) contrary to recent perception, from a national perspective the great majority of burning in any one year typically occurs in the tropical savannas; (2) the distribution of burning across the savannas is very uneven, occurring mostly in sparsely settled, higher rainfall, northern coastal and subcoastal regions (north-west Kimberley, Top End of the Northern Territory, around the Gulf of Carpentaria) across a variety of major land uses (pastoral, conservation, indigenous); whereas (3) limited burning is undertaken in regions with productive soils supporting more intensive pastoral management, particularly in Queensland; and (4) on a seasonal basis, most burning occurs in the latter half of the dry season, typically as uncontrolled wildfire. Decadal fine-resolution fire histories have also been assembled from multi-scene Landsat imagery for a number of fire-prone large properties (e.g. Kakadu and Nitmiluk National Parks) and local regions (e.g. Sturt Plateau and Victoria River District, Northern Territory). These studies have facilitated more refined description of various fire regime parameters (fire extent, seasonality, frequency, interval, patchiness) and, as dealt with elsewhere in this special issue, associated ecological assessments. This paper focuses firstly on the patterning of contemporary fire regimes across the savanna landscapes of northern Australia, and then addresses the implications of these data for our understanding of changes in fire regime since Aboriginal occupancy, and implications of contemporary patterns on biodiversity and emerging greenhouse issues.

Although biomass burning of savannas is recognised as a major global source of greenhouse gas emissions, quantification remains problematic with resulting regional emissions estimates often differing markedly. Here we undertake a critical assessment of Australia’s National Greenhouse Gas Inventory (NGGI) savanna burning emissions methodology. We describe the methodology developed for, and results and associated uncertainties derived from, a landscape-scale emissions abatement project in fire-prone western Arnhem Land, northern Australia. The methodology incorporates (i) detailed fire history and vegetation structure and fuels type mapping derived from satellite imagery; (ii) field-based assessments of fuel load accumulation, burning efficiencies (patchiness, combustion efficiency, ash retention) and N : C composition; and (iii) application of standard, regionally derived emission factors. Importantly, this refined methodology differs from the NGGI by incorporation of fire seasonality and severity components, and substantial improvements in baseline data. We consider how the application of a fire management program aimed at shifting the seasonality of burning (from one currently dominated by extensive late dry season wildfires to one where strategic fire management is undertaken earlier in the year) can provide significant project-based emissions abatement. The approach has wider application to fire-prone savanna systems dominated by anthropogenic sources of ignition.