Two major bushfires in December 2001 and January 2003 were the most significant events in the reporting period. The latter was the larger fire, burning 70% of the ACT. The intensity of the 2003 fires resulted in severe impacts to ecological communities in the western part of the ACT, and to the infrastructure and psyche of Canberra and its people.
Environment ACT post-fire surveys in 2003 documented and assessed the initial impacts of the fires on natural ecosystems. They showed that while broad-scale recovery will occur, this will take some time and there is concern for particular ecological communities and component species, for example, sub-alpine bogs, Black Cypress Pine woodland, the Northern Corroboree Frog, threatened native fish species, in the upper Cotter catchment.
The ACT fires in January 2003 were part of a series of bushfires that burnt substantial parts of south-eastern Australia, evoking widespread public concern and official inquiries, the outcomes of which are likely to impact on future management of areas set aside for nature conservation purposes.
Two major bushfires in December 2001 and January 2003 had a major impact upon the ACT and region. The January 2003 fire was the most significant fire in the ACT for many years and part of a series of bushfires that burnt almost four million hectares in south-eastern Australia (House of Representatives Select Committee on the recent Australian Bushfires 2003).
In the ACT, the 2001 fires (3411 hectares) affected mainly rural land and softwood plantations, while the 2003 fires affected 164,914 hectares (see map) caused major loss of private housing, infrastructure, softwood plantation, and publicly owned facilities. The 2003 fires burnt 70% of the ACT, including 90% of Namadgi National Park, virtually all of Tidbinbilla Nature Reserve and the Murrumbidgee River Corridor Nature Reserves, and about 18% of Canberra Nature Park. Five of the nine ACT river catchments were burnt—all or almost all of the Cotter, Gundgenby–Naas and Paddys River catchments, and parts of the Molonglo and Murrumbidgee River catchments.
In the 2000–01 fire season, 185 hectares were burnt by bushfire. In the 2001–02 season, 3411 hectares were burnt with pine plantation the most affected (1055 hectares). Areas of Canberra Nature Park were also burnt: Red Hill (162 hectares), Bruce Ridge (84 hectares), and Wanniassa Hills (17 hectares). In the 2002–03 fire season some small fires were recorded prior to the extensive fires of January 2003 in Namadgi National Park and the Murrumbidgee River Corridor.
The severity of fires in the Cotter catchment is listed below.
ECOWISE Environmental has mapped fire severity in the Cotter catchment (which contains ACT water supply storages of Cotter, Bendora and Corin reservoirs) using Landsat ETM+ imagery (Bands 4 and 7). Four fire severity classes were recognised:
- Very high fire severity (complete canopy defoliation, no leaves remaining). This level of severity was widespread in the northern half of the catchment, in particular the large area of softwood plantation, and in two areas southeast of Corin Dam. There are also smaller patches, some associated with ridgelines. Vegetation affected is wet sclerophyll forest, dry sclerophyll forest and smaller areas of sub-alpine woodland.
- High fire severity (total canopy scorch, leaves brown but remaining attached). These are mainly adjacent to the large patches identified above. There are other areas some associated with ridgelines.
- Moderate fire severity (partial canopy scorch, upper canopy green)
- Low fire severity (canopy intact, understorey burn only).
These last two categories include an area of wet sclerophyll forest northwest of Bendora Dam, and the area from northwest of Corin Dam to the southern ACT border. The latter is interspersed with small patches and linear areas that are more severely burnt.
The results of surveys (Carey et al. 2003, Ch. 3) suggest that populations of most species were substantially reduced in fire-affected areas (see Table 1).
Survival was related to fire severity (see box on page 3) with a range of species still present in less severely burnt areas. There is evidence that some animals (for example, reptiles and Lyrebirds) survived the fires, but died later, possibly due to lack of food and shelter and increased predation. Species with small isolated populations largely restricted to fire-affected areas have a higher risk of becoming locally extinct and these species include the Northern Corroboree Frog Pseudophryne pengilleyi , Smoky Mouse Pseudomys fumeus , Alpine Grasshopper Kosciuscola menistra and Yellow-bellied Glider Petaurus australis .
The major implications of the fires for ACT fish species are the threats posed by increased sedimentation of streams from erosion in the affected catchments. In February 2003, three fish kills were reported in the region following rain in the catchment. These were at ‘Fairvale’ property (Murrumbidgee River upstream of the junction with the Cotter River), Cotter River below Cotter Dam and at ‘Coodravale’ property (NSW) on the Goodradigbee River upstream of Wee Jasper.
Fish surveys showed a substantial reduction in fish numbers compared with numbers in previous surveys at the same sites. Streams of particular concern are those in the Cotter catchment where there are populations of four threatened fish species (Macquarie Perch, Macquaria australasica; Trout Cod, Maccullochella macquariensis; Twospined Blackfish, Gadopsis bispinosus; and Murray River Crayfish, Euastacus armatus). Specific sampling for the threatened Two-spined Blackfish found a decline of almost 70% from 2001 results (Carey et al. 2003, p.53).
Of the 35 plant species surveyed, no plants of Gentiana baeuerlenii were found (none have been sighted since 1998); no recovery was evident from Pomaderris pallida , Callitris endlicheri and Acacia alpina ; and the only known White Box Eucalyptus albens tree in the ACT appears to have been killed, with no seedling regeneration at time of survey.
Eleven of the 13 wetlands of national importance in the ACT are located in Namadgi National Park and all were burnt in the January 2003 fires.
Visual, on-ground estimation suggests all the wetlands were extensively burnt. The lowest proportion (approximately 70%) was for Ginini Flats but this was severely burnt with up to 30 centimetres of peat destroyed (Carey et al. 2003, p.56). At Snowy Flats, increased mortality of Burrowing Spiny Crayfish, Euastacus rieki, was recorded, which may be due to fox predation.
The most serious impact that may have long-term effects on the wetlands is the loss of hummockforming Sphagnum Moss, Sphagnum cristatum, which, at Ginini Flats, has a growth rate of 3.5 centimetres per 100 years (Hope et al . 2003 in Carey et al . 2003).
The surveys reported in Carey et al. (2003) also showed that a significant number of plant species were showing signs of recovery especially the fire tolerant species.
Species sensitive to certain fire regimes (‘seeders’) such as Alpine Ash and Black Cypress Pine showed no recovery where the canopy had been scorched or removed. Dry Rocky Heath was the community with the least signs of regeneration. This may have been related to ongoing drought. Some forb species, including the endangered Small Purple Pea at Mt Taylor were on the point of flowering (see Table 2 for a summary of vegetation reports).
Some five months after the fires, eucalypt species at many riparian survey sites were demonstrating strong regrowth from epicormic shoots. However, eucalypt regeneration at higher altitude appears to be more from lignotuber than epicorms. This may result in a longer delay before shading is restored to streams. There are signs of recovery in streamside shrub species.
More than 840 kilometres of riparian vegetation in ACT catchments was burnt, with about twothirds of this at high or very high severity (Carey et al. 2003). Vegetation cover was also lost from substantial parts of the east and northeast of the ACT’s water catchments.
The result was that intense rainstorms in February 2003 washed massive amounts—27 years’ worth—of sediment burnt organic and mineral material from riparian zones, streambanks and hillslopes into most streams in the catchment and into the Bendora, Cotter and Corin reservoirs.
For the first time, sheet erosion became the dominant sediment for Corin Dam and, although not calculated, is estimated to be well in excess of 50 per cent of the total sedimentation. This compares with seven per cent before the fires.
ACT water supply dams (Bendora, Corin and Cotter) were sufficiently polluted by all this to be closed by April 2003. They had not been reopened for water supply purposes by the end of 2003. Canberra and Queanbeyan residents have sourced their drinking water from Googong Dam since that time. These impacts will be expressed for a number of years as vegetation establishes again and surface condition stabilises.
The impacts of the January 2003 bushfires are still being felt throughout the entire ACT community. Many of the 488 houses destroyed by fire have not yet been rebuilt, some pine forests will never be replanted, and the future of the rural villages is still uncertain.
Some icons such as the Tidbinbilla Education Centre, Mt Stromlo Observatory and Mt Franklin chalet may be re-built, but the timing is unknown.
While the bushfires did bring out the sense of community amongst ACT residents, many people are still recovering emotionally. The ACT economy was also affected by the need to divert funding to manage a difficult and complex recovery operation, and by the sudden increase in demand for housing.
An unexpected outcome of the fires was that many previously unrecorded Aboriginal and historic sites were located, while some known sites were found to be more extensive than previously recognised.
The bushfires of January 2003 brought the question of fire management in conservation reserves to the fore. Much of the discussion and questioning derives from the expectation that a bushfire threat can be ‘tamed’ and unplanned fire can be controlled and extinguished.
This is based on the twin approaches to fire management developed over the last 50 years of fire suppression (aided by major advances in technology) and prescribed hazard reduction burning at low intensities (Gill et al. 2002). Sometimes added to this are assumptions about Aboriginal burning regimes prior to European settlement. The environmental impact of Aboriginal landscape burning remains one of the most complex and contentious issues in Australian ecology (Bowman 1998).
Major fire events can be both catastrophic and perplexing. They are the result of both nature and the history of human land use, in that they burn a human forest legacy and may be more ferocious as a result (Griffiths 2002; Lindenmayer 2000).
Many of the areas in southeastern Australia burnt in 2003 suffered similarly severe bushfires in 1939. In Victoria, the ‘Black Friday’ bushfires were the subject of a Royal Commission headed by Judge Leonard Stretton (Stretton 1939).
Stretton grappled with the question of whether long-term exclusion of fire was feasible in scrubby, fire-prone forests or whether regular, short-term controlled burning was necessary, even though controlled burns resulted in the maintenance of fire-prone shrub growth. He concluded that exclusion of fire was impossible in European Australia, but regular controlled burning was realistic (Griffiths 2002). However, establishing such a regime would not be easy in wetter forests which are only occasionally dry enough to carry a fire and probably evolved through a regime of less frequent fires of higher intensity.
The ACT Government land management agencies prepared a Bushfire Fuel Management Plan for 2002–04 (effective 1 December 2002) incorporating the results of a review, and consideration of the effects of the December 2001 bushfires in the Stromlo area. Among other things, the plan called for increased strategic fuel reduction in pine plantations and the Namadgi National Park (which will need further review following the January 2003 fires).
All bushfire plans should take into account biodiversity requirements as much as other factors.
No prescribed burning was undertaken in the ACT between 1 July 2000 and 31 December 2002. Commencing in autumn 2003, the ACT carried out fuel reduction in areas not affected by the January 2003 bushfires. This program will continue into summer 2004 and involves prescribed burning, mowing and slashing, physical or mechanical removal of material, fire-trail maintenance and tree surgery.
Activities are notified through the news media including the regular ‘Bushfire Recovery Information’ notice in The Canberra Times .
As part of the argument for more hazard reduction burning, it has become popular to incautiously invoke concepts of Aboriginal ‘fire-stick farming’ across the whole of the Australian landscape as a suggested basis for modern fire management.
These generalisations have become part of the politics surrounding management of public lands such as national parks, and vegetation clearing controls on private land involving ‘regrowth’ (Griffiths 2002). What understanding there is of the fire ecology of the ACT suggests a different Aboriginal burning regime in lowland woodland to the high mountain ranges.
Relating fire management to current management goals, while attempting to unravel past fire regimes and their relationship to current vegetation patterns, will be more productive than invoking elusive pre-European fire regimes as the model for the future.
The January 2003 bushfires in the ACT provide an opportunity to monitor and carry out research on post-fire recovery of species and ecological communities. Long-term monitoring, documenting, reporting, analysis and review provide the basis for understanding the environment and the effects on it of disturbance regimes. This knowledge would enable a clearer link to be made between vegetation characteristics and fire regimes and be invaluable for future land management.
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