Bushfire may be the most extreme ecological change we can witness, it is destructive, it is inevitable, and it is necessary. Fire is essential to the ecology of most plant communities in the Royal National Park. Our flora is largely adapted to fire with strategies to regrow and reproduce after a fire event. Many plants depend on this fire response to complete the life cycle. Some marsupial reproduction may also be geared to take advantage of the green pick that flourishes after fire. In past millennia under aboriginal care there have been seasonal fires lit with the purpose of increasing accessibility and the productivity of the country. There is good reason to assume that our notion of an ideal natural environment should include more fire, but there are limits:
- Too hot. Fire that escapes into the canopy of the trees will kill a range of plants and the animals that take refuge in treetops. When the landscape is renewed there will be a suite of plant and animal species missing, diversity will suffer.
- Too extensive. Fire that is uncontrolled will burn longer and further, the sheer scale of destruction will produce additional destructive effects. Where fires are controlled and restricted to a small scale there is a mosaic pattern of burnt and unburnt land, this allows for movement of animals between different areas and recolonisation after fire. Likewise, plant species that are burnt in smaller patches will be more likely to re-establish after fire. In a parcel of bushland surrounded by a cleared landscape there can be little re-colonisation from the surrounding area.
- Too frequent. The re-establishment of life after the fire takes time. Plants that regrow from seed take time to mature and set new seed, animals also take time to recolonise after the plant life rebounds. The fire alters the physical landscape too, soil and rocks are baked, beds of ash cover the hills and move into the creek beds, all this takes time to return to stasis.
Controlled ecological burns do take place in the Royal under the National Park and Wildlife Services. These fires are infrequent and subject to limited staff numbers and equipment, by comparison the Rural Fire Service is well resourced. The RFS is given the responsibility to conduct hazard reduction burns to protect housing adjoining bushland. When fire in the park is out of control command is given over to the RFS and while the NPWS will continue to assist, the task of managing risk and taking strategic decisions rest with the RFS. The priority of the RFS is to protect human life, of the public and of the firefighters, then to protect property. Risking life to protect the bush is perhaps a low priority. Putting out the fire is the objective and this should be done safely and as easily as possible. Ecological objectives are not forgotten but they are weighed up somewhere in the mix. There are a raft of issues that create a tension between good ecological management and effective fire control, remembering that poor fire control can lead to disastrous ecological outcomes:
- Back burning. One way to stop a fire is to remove fuel in its path. If there is sufficient time, and the wind feeding the fire is favourable, and if there is good access, it is then easy to set a line of controlled fire that will advance towards the oncoming wildfire. When the two fires meet they will subside having burnt everything on the fire ground. The back burn will usually be set where there is vehicular access to allow for water tankers to protect the fire fighters and guard against the possibility that the back burn will itself go out of control. This strategy means that a large area of land may be burnt between the back burn and the wildfire and fleeing wildlife will be trapped between the two fires. The back burn may be set on land that would not necessarily burn if left alone. Perhaps a gully with moist vegetation that would not necessarily set fire by normal ember attack, and this artificial fire will be burn with greater speed, uphill rather than down, again trapping escaping wildlife. Again the cost of doing nothing must be weighed against the cost of taking practical action. There may be alternative strategies, like proceeding into the bush away from the protection of the tankers, but this carries greater risk, again an exercise in balancing costs.
- Water. Another way to put out a fire is to douse it with water, if that water comes from the ocean it will contain salt that will stay in the soil and prevent plants from growing. The bare landscape will then be open to erosion and soil will be lost and watercourses will be choked with increased sediment. The tankers refill from fresh water sources, weirs and hydrants, but the choppers are able to scoop water from the beaches, and where the ocean is close it may save valuable flying time. An Erickson skycrane was filmed taking seawater from Garrie beach for the Curra Moors fire and there was some minority social media comment made about the damage to the environment. The public appetite seemed to be extinguish at any cost, but it was reassuring that RFS Sutherland fire control were quick to post other clips and shots of choppers taking water from freshwater sources. Using saltwater is a known problem and should be an option of last resort. It may be that the RFS fire control is more open to ecological concerns than the general public. When it comes to the fear of fire the bush becomes an enemy and those who are concerned for the bush become caught in an ideological war where lives and houses are seen to trump all other concerns, no matter how distant the fire threat may be.
- Fire retardant. The most expensive way to deal with fire is to use a chemical retardant. In this fire retardant was spread by use of a Very Large Air Tanker, a modified DC8, with a reputed cost of $40000 per drop of bright pink retardant. While not as damaging as salt water the retardant does contain high levels of ammonia which will alter the growing conditions for plants, especially in or near the waterways. Here are some extracts from an RFS factsheet on fire retardants:
The NSW RFS drops fire suppressant retardants and gels such as Phos-Check®, Blazetamer and Thermo-Gel from aircraft during firefighting operations to help slow the spread of a fire.
Long-term fire suppressants such as retardants are essentially fertilisers (ammonium and diammonium sulphate and ammonium phosphate), with thickeners (guar gum) and corrosion inhibitors (for aircraft safety).
Sometimes a red coloured pigment, made from iron oxide, is added so that those spraying can see where they have released the fire retardant. Examples are Phos-Chek MVP-fx and Phos-Chek 259-F.
Short-term fire suppressant foams are made of a combination of wetting agents and foaming chemicals, mixed with water. This allows the water to penetrate surfaces more easily. Their usefulness is limited against high-intensity fires, where long-term retardants have proven more successful. Examples are Angus ForExpan S, and Phos-Chek WD-881.
- Containment. When the fire is surrounded by burnt out land the fire will subside and eventually die out. After the flames die there will be trees and logs that continue to smoulder and gusty winds can restart new fires. This protracted period of danger can be shortened if all land within the containment lines is burnt out quickly. The burning can be accelerated by the use of aerial incendiaries. This need to bring the fire to a quick end may run counter to good ecological management, it may be better if the fire ground retained patchy areas of burnt and unburnt vegetation.
Clean Up. After the fire there is further work to be done that may have environmental consequences. Burnt trees are sometimes unstable and may represent a risk to the public if they were to fall on the roadway; black tree, black road – an accident waiting to happen. These burnt trees also have habitat value for wildlife, many birds, bats and possums nest or roost inside the shelter created by the sculpting effect of fire. Many species are entirely dependent on these hollows to reproduce. It would be good if tree felling after the fire was sensitive to these ecological values.
Contaminants will arise from the destruction of infrastructure. There was a time when all the “hardware” in the park was made of timber or steel, but now the use of plastics has gained a foothold. Roadside markers are now made of plastic and these wilt in the radiant heat, but more worrying are the kilometres of fibreglass footpaths that turn into fine filaments that will remain as permanent detritus in the park. The walk to Wedding Cake rock was unaffected by this fire but the section of new track north of Garrie beach has been burnt out. Clean up will involve careful raking and removal of all affected topsoil.