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RANGE MANAGEMENT NEWSLETTER
Official newsletter of the Australian Rangeland Society
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Author family name, initials (year). Title. Range Management Newsletter Number/issue, pages (Australian Rangeland Society, Australia).
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Bastin, G. and Allan, G. (2012). After the smoke has cleared: 2011 fire in central Australia. Range Management Newsletter N0. 12/2, 3-6. (Australian Rangeland Society, Australia).
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After the Smoke has Cleared: 2011 Fire in Central Australia
Gary Bastin, ACRIS Coordinator, CSIRO Ecosystem Sciences, PO Box 2111, Alice Springs NT 0871
Grant Allan, Bushfires NT, PO Box 2533, Alice Springs NT 0871
Last November, one of us (Grant) reported to an Alice Springs audience on fire activity and emerging lessons in central Australia during the latter part of 2011. That talk was part of the 2011 Rangeland Journal Lecture Series and is available to Australian Rangeland Society members (along with those of other guest lecturers) through the Society’s web site.
The fire threat has now eased, at least for the time being, and ACRIS can now report regional fire activity during 2011 in central Australia relative to other rangeland regions and to previous years. For those not familiar with ACRIS, it is the Australian Collaborative Rangelands Information System. Thematic biophysical and socio-economic data and information about change in the rangelands can be found at our web site, http://www.environment.gov.au/land/rangelands/acris/index.html.
Data source
Fires are monitored using satellite data. Two web sites are commonly accessed for current fire activity: the North Australian Fire Information, NAFI (http://www.firenorth.org.au/nafi2/) and Sentinel (http://sentinel.ga.gov.au/acres/sentinel/index.shtml). After the smoke has cleared, fire scars are mapped to determine burnt area, return time or frequency of fire, and other spatial statistics related to burnt area.
The WA Land Information Authority (Landgate) has mapped fire scars across Australia on a monthly basis since 1997. Landgate uses data generated by the NOAA AVHRR series of satellites which has a pixel resolution of 1.1 km x 1.1 km. These large pixels are suitable for mapping extensive fire but are less sensitive where fires are small or the burn is patchy. The AVHRR-sourced data are well suited to the rangelands-wide reporting that ACRIS undertakes.
Wildfire follows big rains
This is an obvious statement for most of the northern savannas, with fires returning each year during the dry season. Wildfire is more episodic in the arid zone but is related to successive years of above-average rainfall. The rainfall and burnt-area maps in Figure 1 show remarkably close spatial coupling between two-year antecedent rainfall and fire extent for the two most recent big wildfire events in central Australia.
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Figure 1. Rangeland area burnt in 2001-02 and 2011 (bottom) and cumulative rainfall between April and March of the two preceding years (top).
Fires in central Australia
ACRIS reports most biophysical data by bioregion or sub-region. There are 52 bioregions wholly or partly in the rangelands (using the Interim Biogeographic Regionalisation for Australia, IBRA v6.1). For the six bioregions in central Australia that experienced extensive fire in 2011, fire was more common between 1997 and 2011 in the two northern IBRAs (Tanami and Davenport Murchison Ranges, Figure 2) and infrequent in the more arid interior (Finke and Simpson Strzelecki Dunefields). The location of bioregions is shown in Figure 3.
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2011 fire extent
≤300 mm
≥2500 mm
2001 fire extent2002 fire extent
Fire was more extensive in the Simpson Strzelecki Dunefields in 2011 compared to other years since 1997. Lightning was the primary source of ignitions during both 2001-02 and 2011, but the 2001-02 fires were restricted to the northern portion of the bioregion.
Figure 2. Percentage of IBRA area burnt each calendar year and decile summer rainfall (November-April) for six bioregions in central Australia.
Similar areas of the Finke bioregion were burnt in 2002 and 2011, but the spatial patterning was different. Extensive areas of pastoral land south of Alice Springs were not burnt last
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Tanami Davenport Murchison Ranges
Burt Plain MacDonnell Ranges
Finke Simpson Strzelecki Dunefields
year and have a high fire potential in 2012. Fire was mostly absent in the Finke bioregion in other years.
Further north in the southern NT, similar proportions of the MacDonnell Ranges and Burt Plain IBRAs burnt in 2011 compared with the combined extent of fires in 2001-02. In both bioregions, the previous big fire season extended over two calendar years, i.e. a considerable proportion of the Burt Plain burnt in 2001 (less so in 2002) and parts of the MacDonnell Ranges also burnt in 2001. This pattern continued further north in the Tanami and Davenport Murchison Ranges IBRAs with a proportionally large area burnt in 2011, considerable portions burnt between 2000 and 2002, and >15% of IBRA area burnt in some of the intervening years. The fires during 2006-07 were associated with two-years of above-average rainfall in these northern bioregions of central Australia but the rainfall did not extend as far south as Alice Springs and influence the fire potential of the four southern bioregions.
Figure 3. Location of central Australian bioregions used for reporting 2011 fire statistics.
Fire activity in 2011 was concentrated between August and November (Figure 4) although the fire season started a little earlier in the northern bioregions. With the exception of several fires started by lightning in late January, the majority of the fire activity between March and July was prescribed burning undertaken to reduce fuel loads and protect assets ahead of the expected high fire potential across central Australia later in the year.
After the fires
It is difficult to directly compare the 2001-02 fire season with that of 2011, although the combined spatial extent of the fires was similar. The fires in 2001 were primarily north of Alice Springs and persisting soil moisture and post-fire rainfall helped pasture recovery. In contrast, the 2002 fires occurred at the end of the period of above-average rainfall. In
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SSD
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BRT Burt PlainDMR Davenport Murchison RangesFIN FinkeMAC MacDonnell RangesSSD Simpson Strzelecki DunefieldsTAN Tanami
general, many of the 2002 fires had a greater impact on the woody vegetation communities and pasture recovery was restricted by the dry conditions that followed (indicated by decile rainfall values for bioregions in Figure 2). At a particular location, Alice Springs received below-average rainfall for the seven-year period from July 2003 to June 2009.
Figure 4. Percentage of IBRA area burnt each month throughout 2011 for six bioregions in central Australia.
It is too early to determine the ecological implications of the 2011 fire season and further fires that are anticipated in 2012. To date, the direct effect of the 2011 fires on the pastoral industry appears to be more subdued than those of 2002, although the cost of fire response in both years was significant. Above-average rainfall this past summer appears to have
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promoted good ground cover across much of the country burnt last year and allowed affected pastoralists to maintain their grazing enterprises without enforced destocking. However there is potential in many areas for a second, short-interval, fire season. In contrast to 2011, these follow-up fires should be more localised and primarily in run-on areas, areas that have received higher localised rainfall and areas of dense buffel grass (Cenchrus ciliaris). The impact of these short-return fires on pastoral enterprises and landscape ecology is uncertain.
More generally, fires are anticipated on pastoral land unburnt in 2011. The likely return to more ‘normal’ conditions of highly variable rainfall could mean reduced pasture recovery post these fires. Beyond the pastoral country, fires are also anticipated on Aboriginal-held land in the south western NT (Great Sandy Desert and Central Ranges bioregions) following above-average rainfall between 2010 and 2012 and the recent absence of extensive fire in 2011. Fortunately this tri-state border region recently received funding assistance through the Australian Government Caring for Our Country program to help Aboriginal land managers to collaboratively manage fire to reduce the risk of large scale wildfires, retain and improve biodiversity, protect threatened species habitat and protect significant cultural assets.
Last word
Fire activity in central Australia in 2011 demonstrated the positive outcomes of research conducted by the Desert Knowledge Cooperative Research Centre in the mid ‘noughties’ (Turner et al. 2008, Edwards et al. 2008). In particular, the data confirm that extensive wildfire follows successive years of high summer rainfall. The largest areas were burnt between August and November with fire activity abating in December with the return of moderate rainfall (>10 mm falling over much of inland Australia, see http://www.bom.gov.au/jsp/awap/rain/archive.jsp?colour=colour&map=totals&year=2011&month=12&period=month&area=nat, accessed 28 May 2011).
Despite the extensive area burnt in 2011, the future remains bright. The capacity for prescription fire management increased substantially between 2002 and 2011. The greatest increase was associated with the extensive areas of Aboriginal Land Trusts through the Indigenous Ranger program of the Central Land Council. The prescriptive fire program on NT parks and reserves has been maintained over the past decade. Both groups undertook aerial burning in 2011. Although staff struggled to match the scale of prescriptive programs to the anticipated fire potential across the extensive area of central Australia, the continued expansion of the ranger programs will provide significantly more capacity to deal with future fire events.
Acknowledgements
ACRIS purchased rangelands-wide fire data from the WA Land Information Authority (Landgate) with funding from the Australian Government through its Caring for our Country program. This funding is managed by Ninti One Ltd.
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References
Turner, D., Ostendorf, B. and Lewis, M. (2008). An introduction to patterns of fire in arid and semi-arid Australia, 1998-2004. The Rangeland Journal, 30, 95-107.
Edwards, G.P., Allan, G.E., Brock, C., Duguid, A., Gabrys. K. and Vaarzon-Morel, P. (2008). Fire and its management in central Australia. The Rangeland Journal, 30, 109-121.
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