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ACRIS Fire Product Update 2006-2010 Updated information to that provided in

Rangelands 2008 – Taking the pulse

Gary Bastin, ACRIS Management Unit CSIRO, PO Box 2111, Alice Springs NT 0871

(email: Gary.Bastin@csiro.au)

This project is supported by Ninti One Limited, through funding from the Australian Government's Caring for ou Country.

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The views and opinions expressed in this publication are those of the authors and do not necessarily reflect those of the Australian Government or the Minister for Sustainability, Environment, Water, Population and Communities. While reasonable efforts have been made to ensure that the contents of this publication are factually correct, the Commonwealth does not accept responsibility for the accuracy or completeness of the contents, and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this publication.

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Mapping of fire scars from NOAA AVHRR satellite data by the WA Land Information Authority (Landgate) allows ACRIS to periodically update the fire record for the rangelands. This brief report updates the rangelands-wide fire record between 2006 and 2010 and follows the presentation style used in Rangelands 2008 – Taking the pulse (Bastin et al. 2008) for reporting fire regime between 1997 and 2005.

Key points

The continued mapping of fire scars from satellite imagery has allowed ACRIS to update the fire record for 2006 through 2010. A complete fire record for the rangelands now exists between 1997 and 2010. Fire extent and frequency continue to vary considerably across the rangelands. Notable differences include:

• Fire continues to be widespread and frequent in much of northern Australia when there is little rain during the dry season. Much of this burning appears to be uncontrolled, occurring in the late dry season when fires are more extensive and quite intense. However there is evidence for some northern bioregions that the extent of cooler fires in the early dry season is increasing. Such burning should mitigate the extent and severity of hotter fires in the late dry season.

• Fire was relatively more extensive in north east Queensland in 2008 and 2009 following high rainfall over the preceding summers. For example, 3.8% and 4.7% of the Brigalow Belt North and 5.0% and 6.0% of the Desert Uplands bioregions burnt in 2008 and 2009 respectively. Median annual fire extent (between 1997 and 2010) for the Brigalow Belt North is 0.7% and for the Desert Uplands, 1.9%.

• In the semi-arid and arid parts of central Australia, there has been little recent fire activity. This region last experienced extensive episodic fire, particularly in the western deserts, following the sequence of wetter years at the start of the most recent decade.

• Fire was generally minimal and infrequent across most of the southern rangelands.

Fire extent

Northern bioregions continued to have much of their area burnt in each of the calendar years 2006-2009 (Figure 1) with fire extent considerably reduced in 2010. This reduced fire incidence in 2010 was probably due to rainfall persisting into the early dry season (April and May) and the following wet season starting early (limited rainfall between July and September with amounts increasing in October and November, Figure 2).

In those recent years when fire was more extensive (2006-2009), the Pine Creek bioregion had the largest proportional area burnt in each year (average 55.7% of bioregion area burnt each year). Between 39% and 43% of the Victoria Bonaparte, Central Arnhem, Northern Kimberley and Daly Basin bioregions burnt on average each year between 2006 and 2009.

There was a similar pattern of annual fire extent at sub-IBRA resolution: fire was less extensive in 2010 compared with the four preceding years. Averaging fire extent across this period (2006-2009), fire was most extensive in the Northern Holroyd Plain subregion of the Cape York Peninsular IBRA (61.5% area burnt each year) followed by the Pine Creek IBRA,

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Victoria Bonaparte P2 sub-IBRA and Weipa Plateau (Cape York Peninsular) (51% to 56% of sub-IBRA area burnt, on average, each year). Maps of annual fire extent by sub-IBRA are shown in Appendix 1.

Figure 2. Spatially averaged monthly rainfall for the northern fire-intensity region (see map included with Box 1 for region extent). Rainfall is shown for 2010 and the long-term median (1890-2010).

Data: Bureau of Meteorology. Graphs: the ACRIS-MU.

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Figure 1. Fire extent shown as the percentage area of bioregions burnt between 2006 and 2010. Corresponding maps of percentage area burnt between 1997 and 2005 are at page 72 of Rangelands 2008 – Taking the pulse.

Data: WA Landgate. Maps: ACRIS-MU.

bioregion not burnt

no data

>60% of bioregion burnt

1% or more ofbioregion burnt0

15

30

45

60

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Box 1: Monitoring fire scars in the rangelands

The extent of fire scars has been mapped on a monthly basis using satellite imagery covering most of Australia’s rangelands. These satellite data are acquired by the WA Land Information Authority (Landgate) and provide a course national overview of fire using NOAA AVHRR (1.1 km x 1.1 km). This technology is less sensitive to small scale or patchy burns, and results from some prescribed or ‘cool’ burns at this scale may not be detected given its coarseness.

Landgate has provided updated statistics on the monthly and annual extent of fire scars in each rangeland bioregion, by sub-IBRA region, for each year since 1997. Fire frequency is a spatial averaging of the number of times an area (pixels in a satellite image) burnt over the 14 years between 1997 and 2010 (see Box 2 for example calculations).

At the regional scale, fire data were highly reliable based on ground checks, acknowledging the difficulties in mapping small fires with the coarse resolution of the AVHRR data. Also, ‘cooler’ burns may be difficult to detect, particularly where there was tree cover and the crown was not burnt (e.g. woodlands). For regional reporting, these limitations in mapping fire scars are less critical than for local evaluations.

Fire intensities were evaluated as being hot or cool depending on the month in which a fire occurred in northern versus central and southern rangeland regions (below map), where:

Regional Grouping Fire Intensity Months

Northern Hot August to December

Cool January to July

Central & Southern Hot December to March

Cool April to November

Geographic grouping of bioregions for categorising fire intensity

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Fire intensity

Fire intensity was defined for Rangelands 2008 – Taking the pulse by month of burn (details in Box 1). The most recent data are included for the four example bioregions used in that report to illustrate differences in fire intensities across Australia’s rangelands (Figure 3).

Regional fire intensities since 2005 for the four bioregions lie within the range that had operated over the preceding nine years (i.e. 1997-2005).

• ‘Hot’ (i.e. late dry season) fires were extensive in the Central Kimberley bioregion between 2006 and 2009 relative to the 1997-2005 fire regime with very little fire in the latter part of 2010 due to increased rainfall. The area burnt by cooler fires was relatively stable between 2007 and 2010 with ~10% of bioregion area burnt each year.

• Hot fires continued to predominate in the Central Arnhem bioregion in 2006 and 2007 but the proportional area burnt by cooler early-dry-season fires increased appreciably in 2008 and 2009.

• For the Desert Uplands (north east Queensland), there was a spike in the extent of hot fires in 2008 and 2009. Presumably, this was due to wet season rainfall being much above average during the preceding two summers thereby increasing fuel loads.

• There has been minimal fire activity in the Burt Plain bioregion (southern NT) in recent years.

Fire frequency

For each rangeland bioregion, fire frequency was calculated as the number of times each area burnt between 1997 and 2010 (see Box 2 for example calculations). These data were log10 transformed to improve the information content of mapped fire frequency (Figure 4). As reported in Rangelands 2008 – Taking the pulse, the northern rangelands continued to burn most frequently and those in southern areas infrequently. For example, the Pine Creek and Daly Basin bioregions (both northern NT) had the highest fire frequencies (log10 transformed values = 0.871 and 0.806 respectively). Several bioregions in the southern rangelands had a nil or very low fire frequency over the 1997-2010 period.

Fire frequency changes with the length of the reporting period so values for some bioregions in the 1997-2005 period (reported in Rangelands 2008 – Taking the pulse) are different to those for 1997-2010 (Appendix 2).

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Central Arnhem bioregion Central Kimberley bioregion

Desert Uplands bioregion Burt Plain bioregion

Figure 3. Percentage area of selected bioregions burnt by ‘hot’ and ‘cool’ fires in the period 1997-2010.

Data: WA Landgate. Graphs: the ACRIS-MU.

Figure 4. Fire frequency for bioregions burnt between 1997 and 2010. Note that mean fire frequency values for each bioregion are mapped as log10.

Data: WA Landgate. Maps: the ACRIS-MU.

0

10

20

30

40

50

60

70

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

% b

iore

gion

bur

nt

cool burnhot burn

0

5

10

15

20

25

30

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

% b

iore

gion

bur

nt

cool burnhot burn

0

10

20

30

40

50

60

70

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

% b

iore

gion

bur

ntcool burnhot burn

0

1

2

3

4

5

6

7

8

9

10

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

% b

iore

gion

bur

nt

cool burnhot burn

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Box 2. Fire frequency in the rangelands

Fire frequencies over the 1997 to 2010 period for each rangeland bioregion were calculated using the following diagrams supplied by the WA Land Information Authority (Landgate).

Assume that a 3 by 3 array of pixels and lines (below table) represents the area extending across a region. Burnt pixels were represented by the value “1” and unburnt pixels by “0”. In the year 1999, two thirds of the array was burnt and in 2000, a little more than one third was burnt. The fire frequency across the two years is calculated by summing pixel values.

Year 1999 Year 2000 Fire Frequency

0 1 1

0 1 1

0 1 1

0 0 0

0 1 1

0 1 1

0 1 1

0 2 2

0 2 2

Two examples of calculating fire frequencies are presented.

In Example 1, the region is represented by four pixels within the solid line.

0 1 1

0 2 2

0 2 2

The average fire frequency for this example region is (2+2+2+2)/4 = 2.0

In Example 2, the region is represented by six pixels.

0 1 1

0 2 2

0 2 2 The average fire frequency for this region is (0+0+2+2+2+2)/6 = 1.3

The spatially-averaged fire frequency data for bioregions have a large and skewed range. Average fire frequency is relatively high in the north and very low in the south. To improve mapping detail, these data have been log10 transformed by the ACRIS-MU (Figure 4).

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Reference

Bastin, G. & the ACRIS Management Committee (2008). Rangelands 2008 – Taking the Pulse. Published on behalf of the ACRIS Management Committee by the National Land and Water Resources Audit, Canberra. Available at: http://www.environment.gov.au/land/rangelands/acris/index.html

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Appendix 1: Fire extent by sub-IBRA

Maps of the percentage area of each rangeland sub-IBRA burnt annually between 1997 and 2010 are shown below and on the following page.

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Appendix 1. Fire extent shown as the percentage of sub-IBRA area burnt between 1997 and 2010.

Data: WA Landgate. Maps: ACRIS-MU.

bioregion not burnt

no data

>60% of bioregion burnt

1% or more ofbioregion burnt0

15

30

45

60

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Appendix 2: Change in fire frequency by bioregion for two reporting periods

Fire frequency changes with the length of the reporting period so values for some bioregions in the 1997-2005 period (reported in Rangelands 2008 – Taking the pulse) are different to those for 1997-2010.

IBRA Frequency 1997-2010

Frequency 1997-2005

Difference Comments

Arnhem Coast 4.895 3.247 1.648 substantial increase with continuing extensive fire between 2006 & 2009 Arnhem Plateau 3.921 2.66 1.261 moderate increase with extensive fire in 2006, 2008 & 2009, less so in 2007 Brigalow Belt North 1.164 1.096 0.068 low fire incidence, little change in fire frequency Brigalow Belt South 1.114 1.018 0.096 low fire incidence, little change in fire frequency Broken Hill Complex 1.020 1.033 -0.013 low fire incidence, no real change in fire frequency Burt Plain 1.225 1.071 0.154 low fire incidence, small increase in fire frequency Cape York Peninsula 4.453 2.812 1.641 substantial increase with continuing moderately extensive fire in between 2006 & 2009 Carnarvon 1.060 1.052 0.008 low fire incidence, no real change in fire frequency Central Arnhem 5.411 3.787 1.624 substantial increase with extensive fire in 2007 & 2009 and moderately extensive fire in

2006 & 2008 Central Kimberley 4.322 3.646 0.676 small increase - continuing extensive fire in between 2006 & 2009 Central Ranges 1.325 1.31 0.015 low fire incidence, no real change in fire frequency Channel Country 1.093 1.091 0.002 low fire incidence, no real change in fire frequency Cobar Peneplain 1.000 1 0.000 low fire incidence, no change in fire frequency Coolgardie 1.033 1.011 0.022 low fire incidence, no real change in fire frequency Daly Basin 6.397 4.436 1.961 large increase with continuing extensive fire in 2006, 2007 & 2009; moderately

extensive fire in 2008 & 2010 Dampierland 4.432 3.658 0.774 small to moderate increase with continuing extensive fire between 2006 & 2009 Darling Riverine Plains 1.174 1.168 0.006 low fire incidence, no real change in fire frequency Darwin Coastal 5.154 3.56 1.594 substantial increase with extensive fire in 2008 & 2009 and moderately extensive fire in

2006, 2007 & 2010 Davenport Murchison Ranges

1.666 1.321 0.345 moderate fire extent in 2007, less so in 2006 and little fire in other years, small increase in frequency

Desert Uplands 1.223 1.083 0.140 small increase - fire more extensive in 2008 & 2009 Einasleigh Uplands 1.898 1.541 0.356 small increase - fire more extensive between 2007 & 2009 Finke 1.030 1.03 0.000 low fire incidence, no change in fire frequency Flinders Lofty Block 1.000 no fire scars mapped until 2009

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IBRA Frequency 1997-2010

Frequency 1997-2005

Difference Comments

Gascoyne 1.101 1.092 0.009 low fire incidence, no real change in fire frequency Gawler 1.000 1 0.000 very low fire incidence, no change in fire frequency Gibson Desert 1.318 1.12 0.197 small increase - some fires in 2006 reducing in latter years Great Sandy Desert 1.467 1.37 0.098 small increase – moderately extensive fire in 2006 reducing in latter years Great Victoria Desert 1.165 1.13 0.034 low fire incidence, little change in fire frequency Gulf Coastal 4.110 2.752 1.357 moderate increase - extensive fire in 2007 & 2009, less so in 2006, 2008 & 2010 Gulf Fall and Uplands 3.271 2.314 0.957 moderate increase - extensive fire in 2007 & 2009, less so in 2006, 2008 & 2010 Gulf Plains 2.761 2.008 0.754 moderate increase - moderately extensive fire 2006, 2007 & 2009; less so 2008, 2010 Hampton no fire record Little Sandy Desert 1.254 1.16 0.094 small increase with some fire in 2006 & 2007 MacDonnell Ranges 1.014 1.014 0.000 low fire incidence, no change in fire frequency Mitchell Grass Downs 1.187 1.107 0.080 low fire incidence, little change in fire frequency Mount Isa Inlier 1.822 1.337 0.485 small to moderate increase - moderately extensive fire in 2006 Mulga Lands 1.054 1.054 0.000 low fire incidence, no change in fire frequency Murchison 1.101 1.069 0.032 low fire incidence, little change in fire frequency Murray Darling Depression

1.000 1 0.000 low fire incidence, no change in fire frequency

Northern Kimberley 5.614 5.094 0.520 previous fire frequency calculated for 1993-2005 - hence a different comparison period. Extensive fire in 2007 & 2008, moderately extensive in other recent years

Nullarbor 1.014 1.091 -0.077 low fire incidence, no real change in fire frequency Ord Victoria Plain 2.752 2.217 0.535 small increase with moderately extensive fire in 2006, less so in subsequent years Pilbara 1.683 1.448 0.234 small increase - moderately extensive fire in 2006, reduced fire extent in recent years Pine Creek 7.429 4.917 2.512 large increase with continuing extensive fire in all years Riverina 1.000 1 0.000 low fire incidence, no change in fire frequency Simpson Strzelecki Dunefields

1.006 1.005 0.001 low fire incidence, no change in fire frequency

Stony Plains 1.000 1 0.000 very low fire incidence, no change in fire frequency Sturt Plateau 4.059 2.723 1.337 moderate increase with extensive fires in 2006, 2007 & 2009 Tanami 2.251 1.894 0.357 small increase with moderately extensive fire in 2006 & 2007, reduced fire extent since Tiwi Cobourg 3.722 2.403 1.319 moderate increase with continuing moderately extensive fire in all recent years Victoria Bonaparte 4.868 3.599 1.269 moderate increase with continuing extensive fire in 2006 to 2009 Yalgoo 1.000 1 0.000 low fire incidence, no change in fire frequency