The Permacultivator - Journal of Cool Climate Permaculture

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Bushfires

• Planning for Bushfire
• Fire Retardant Plants
• Bushfires and Biodiversity

Planning For Bushfire 

Ralph Long and David Johnson provide a scheme for hazard reduction that is sensitive to the needs of the bush.

Australia’s oil & coal was derived from different foliage than exists today. Climatic change and when the aborigines migrated from the north contributed to the change. Although lightning caused some bushfires the aborigines used fire as a tool, burning some areas regularly and some areas not at all. Most of these fires burnt until they ran out of fuel or rain put them out, the aborigines may have used brushes to beat the flames out or relied on backburning or previous burnt areas for control. From then on only foliage that would regenerate after fire survived. Some can stand fire every year, others need 8-20 years or more without fire in order to reach maturity and produce seed.

Then along came white man with fire carts and trucks and they put natural fires out before they could burn to a natural end. This causes a massive build up of flammable material on the forest floor which normally would have been burnt. So when a fire does get into this material it is mostly uncontrollable, given the right weather conditions. The resulting fire is therefore hotter than usual and thus can result in the extinction of some species of flora and fauna that would normally survive a regular cool fire. Scientists will have to study and advise what amount of time each species needs between fires in order to survive. Then a plan can be worked out for each area of bush for hazard reduction burning. There is also debate whether this should be done in autumn (hot burn, more natural, burns more) or during winter/early spring (cool burn, unnatural and not everything burns [sometimes nothing on south facing slopes] but unburnt material becomes a hazard in summer).

The following is a table that I have worked out for an area of bush, to be burnt on a eight year rotation the time needed for some Banksias to regenerate. With this pattern each area has different fuel loads, and could act as a fire break or have a low intensity fire and enable flora and fauna to survive. Animals etc would have adjacent areas of lower fire risk to which to retreat.

Note that individual areas need not be of even size, only wide enough to provide a firebreak. Preferably divisions and/or firetrails would follow natural barriers or be along contours to minimise soil erosion from thunderstorms. Neighbours or Fire Control Officers could devise local plans so that not everyone burns the same year.

Permaculture has always recognised the need to plan for natural disasters such as bushfire. It is mentioned in PERMACULTURE ONE & TWO, A DESIGNERS’ MANUAL, INTRODUCTION TO PERMACULTURE and PERMACULTURE INTERNATIONAL JOURNAL *32.

David Holmgren, after the Ash Wednesday fires of 1983, produced "A case study in design against bushfire" which was used in an information display which the Victoria Department of Planning and Environment sent around to affected areas. It covers Fire Behaviour, How a House Burns, Choosing the Site, Site Layout, Broad Scale Planting, Water & Fire, Planting & Services, House Design & Construction, Management.

David recommends that in Autumn/Winter "Rake litter in the tree belts and bush edges within the fire sector into contour ridges which catch run-off water and decompose enough not to be a fire hazard by summer. This is more labour intensive than cool burning but is safer and better for the soil." This is a concern I have with council tips accepting organic matter which should be chipped/composted or buried on site to preserve the soil fertility. Buried leaves would not be a fire hazard and when you are covering the first lot of leaves you would be digging the next hole.

Past bad planning may have to be corrected with roads provided on the downhill (bush) side of houses, then perhaps playing fields between the road and the bush. Incidentally in Sydney, fire burnt across a mown playing field which puts paid to the "rednecks" theory that greenie practices were to cause for the fires getting out of control. Given the climatic conditions at the time any fire starting was very likely to be hard to control. Incidentally these rednecks want the right to destroy the one percent area of wilderness that the State Government wants to lock up. Isn’t the other 99% enough for them?

Permaculture says that people should be responsible for their own inputs and outputs (water, energy, rubbish etc) where possible. The fact that Sydney’s Water Board could not supply all areas with water during the fires proves that people would be better off with their own water storage. Also the push by city types in Robertson & Burrawang to be provided water services by Wingecarribee Council could lead to disaster as the supply failed to meet demands without the extra demand of a fire. Your own supply of water and power to transport same onto a roof, for sprinklers, is the only reliable way to fight a fire. This could be a storage tank on a hill higher than the house roof.

Fire retardant shrubs and trees between fire hazards and what you want to protect is another way of reducing the risk. The following are some useful species, double check if suitable for your micro-climate; Cootamundra Wattle, Orange Wattle, Silver Wattle, Blackwood, Cedar Wattle, Saltbush, Kurrajong (frost tender), River She Oak, Carob (drought & frost tender), Tree Lucerne, N.Z. Mirror Bush, Pride of Madeira, Lilly Pilly, Morton Bay & other Native Figs (check for drought/frost tolerances), Ash, Walnuts, Pyramid Tree (frost tender), Bay Laurel, Privet (may be noxious, check), White Cedar, Mulberry. Boobialla, Chinese Hawthorn, Sweet Pittosporum, Plane/Sycamore Tree, Stone Fruits, Poplars, Oak, Willow, Pepper Tree, Tamarisk, Linden, Elm, Most fruit & nut trees.

Fire Retardant Plants in the Permaculture Garden 

Debbie Hebbard on using plants to add to a fire control strategy.

The summer of 97-98 made me more aware of the risk of bushfire than I have been since building 10 years ago. The bush stretching for kilometres to the west of me, is generally made up of phyrophilous or fire dependent species (Mollison). They are basically ‘dry, summer deciduous, thick seeded plants’, including eucalypts, acacias, banksia, hakeas and grevilleas. While I cannot change this area outside my boundaries I can follow Bill’s suggestion and ‘alter the vegetation (within my block) to create a more fire immune system’.

This is of course only one aspect of the whole picture. As David Holmgren states 'bush fire design involves the integration of many elements and careful weighing of the risk factors’. This article will focus on the selection of plants with fire retardant characteristics that can be used as part of the total fire plan.

FIRE RETARDANT PLANTS

Fire retardant species are those plants that, under most conditions, will have several of the following characteristics :

• be slow to ignite and burn,
• deflect radiant heat,
• slow the fire front,
• produce little litter or quickly decomposing litter &
• may have the ability to regenerate afterwards.

Generally the degree of resistance will be influenced by seasonal and environmental conditions, as well as the intensity and duration of the blaze.

It must be remembered that any plant can be damaged or destroyed by fire, if the fuel load is high and / or the fire conditions are extreme enough.

Thus fire resistance is a complex issue.

HOW THEY WORK

All plants will burn eventually. The degree of flammability of foliage depends on the

• moisture content. Most natives have a moisture content of 80 to 150% of their oven dry weight (ODW) while deciduous trees contain 250 to 400% of their ODW. The higher the moisture the slower the ignition. Lush, green material must be dried out by the fire before it will ignite.
• ash content , or the solid matter left after burning. It tends to be made up of alkaline compounds that are naturally fire retarding , so low ash plants like Eucalypts (usually < 10% ash) will glow (and therefore can cause further flare ups) for longer periods than deciduous trees of 30 to 40% ash. This ash cools quickly and can smother remaining hot spots.
• volatile oil content . In Eucalyptus, Melaleuca, Callistemon and other Myrtaceae range up to 5% oil this is generally higher than other plants. When heated this oil can explode, intensifying the heat ahead of the fire front. This in turn heats and ignites more volatile oils.
• ignition temperature. Plants with higher oil levels tend to have lower ignition temperatures, the Myrtaceae family ignite at 80 to 100 degrees C so they burn with less preheating than other species which ignite at 200 to 400 degrees C. Loose, flaky or rough bark will trap embers. This can produce enough heat for ignition.
• salt content ,is more related to location than to species. Plants growing in saline conditions will have a higher salt content and this retards burning.

MANAGING FUEL LEVELS

The most significant factor in preventing a fire is the removal of fuel deposits. The more dried material available, the greater the risk and severity of a fire. Healthy, green vegetation will generally not burn unless it is preheated and dried out first. This occurs when ground litter, (leaves, twigs or bark) and dead material in the lower parts of the crown, are ignited by sparks. The heat and air currents generated by this ground level fire can lead to a crown fire.

There are years when weather conditions are so severe that fires are likely, and their intensity is directly linked to the quantity of fuel available.

Permaculture approaches for fuel reduction could include :

• collecting twigs and fallen timber as kindling / fuel for home heating/cooking,
• using poultry / pigs to scratch and till the litter, this would speed up the decomposition and fertilise the plants
• swales or trenches will slow the movement of burning material across the ground, speed up the decomposition of litter.
• swales will increase the soil moisture content and therefore keep plants greener.
• well mown or grazed grasses are very useful. They may be created by encouraging grazing animals like wallaby or geese into an area with food supplements; or slashing , fertilising and watering an area to produce an appetising grass sward.

PLACEMENT FOR MAXIMUM PROTECTION

In the heat of the battle with any fire there is little time to sit back and observe what is occurring. When the danger has passed, we often find some areas devastated while metres away little damage has occurred. There are many factors contributing to the fires behaviour, all we can do is to use as many features as we can, to protect our sites.

Fire damage is caused by radiant heat, embers and / or the actual flame front. Radiant heat, moving ahead of the fire front can quickly kill plants and animals. It is probably more dangerous than the flames. It will also decrease moisture levels and raise the temperature of materials, making them more easily ignited. Dense planting’s of retardant species, will help to shield the area from radiant heat damage. The resulting fire shadow can protect an area 3 to 4 times the height of the barrier.

Wind blown embers can travel well ahead of the fire and start spot fires. Flammable materials, including plants, near structures can be ignited by these embers or by the fire front as it passes through. Barriers of resistant plants can trap embers , minimising spot fires, and slow the wind speed dramatically.

Other features should be incorporated into the design to help reduce damage by deflecting radiant heat, minimising fuel build-up and generally buffering the house. The use of access roads, dams, well grazed pastures, earth berms and other structures, can significantly reduce the potential for damage.

PLANT SELECTION LISTS!!

My research into fire retardant plants has been interesting. To date I have found reference to over 300 plants with reported fire retardant qualities. Some plants are only mentioned in one text, others turn up in many references, and the value of some plants is clearly disputed. Some authors talk about whole genera eg Atriplex spp, others mention specific plants eg Atriplex cinerea or (grey saltbush), and yet others only use common names eg saltbushes. So I continue to read, collate and research the horticultural requirements of these plants. My goal is to have a list of those plants, reported to be fire retardant and suited to our region, for the next issue. That will give you time to evaluate your site, prepare the areas for planting and by spring be ready to plant some retardant species.

Planning and preparation before the fire season reduces panic later.

And so the siting, selection and planting of fire resistant species will form a part of the overall fire protection plan, in your permaculture system.

REFERENCE LIST

• AUSTRALIAN PLANT STUDY GROUP. 1980. Grow What Where.
• ELLIOT, Gwen. 1996. Australian Garden.
• FRANCIS, Robyn. 1989 Permaculture International Journal issue 32. ‘Design for bush fire’
• HARTSHORNE, Heather. 1995. Plants for Dry Gardens.
• HOLMGREN, David. 1993.The Fly Wire House.
• MOLLISON, Bill. 1988. Permaculture A Designer’s Manual.
• MOLLISON, Bill & LAY, Reny. 1991. Introduction to Permaculture.
• NUGENT, Jeff. 1996. Permaculture Plants.
• SIMPFENDORFER,K.J. 1992. An Introduction to Trees from S.E. Australia.
• WALKER, Warren, Wariapendi Farm Nursery. Tree Talk A guide to planting trees/shrubs.

Table missing

J22 Winter 98

Bushfires and Biodiversity 

Tony Hill investigates the relationship between bushfires and the complex diversity of organisms affected by them.

Bushfires in South Eastern Australia are a part of the natural landscape which is one of the most fire prone in the world. Some plants use fire to their advantage to suppress and even wipe out other species. Wherever eucalypts grow naturally there is likely to be a fire regime with intervals between fires that can vary from one to three years in open grassy woodland to more than 100 years in tall mountain ash forests.
Variety is healthy, whether it is among humans, animals, plants in the garden or the natural environment. Biodiversity strengthens any living system, making it more resistant to being ravaged by disease, creates more niches for different organisms to inhabit, increases the chances of survival, provide a greater variety of resources and provide delight to the spirit and a balm to a troubled soul. Monocultures require a lot more effort and resources to keep going, are more susceptible to pestilence and extinction, cause degradation of the environment and depress the senses by their monotony.
Frequent bushfires, whether wildfires or controlled, are recognised as a key threatening process to biodiversity in New South Wales. Up to ninety percent of bushfires are caused by human activity, with about sixty percent being deliberately lit, so the natural environment is at far greater risk from man than man is from the natural environment. The frequency and severity of bushfires is likely to greatly increase as the human population increases and with the effects of global warming. The New South Wales Government has recognised this risk and placed the protection of the natural environment alongside that of life and property in legislative changes and plans for bushfire management.

Bushfire Management
Bushfires cannot be prevented, and management is aimed at where the bush and the man made structures meet and largely consist of reducing the amount of fuel available for fires and reducing the vulnerability of houses to fire.

•  Hazard reduction burning is widely advocated but is often of limited use and effectiveness. It certainly has its place but not as a universal panacea, and more effective methods of protection from bushfires are often indicated that are less destructive to the environment. Bush on damp soils may not burn except under extreme weather conditions, and then goes up with extra ferocity, and fuel reduction by planned burning is usually impossible.
•  Fuel reduction by other methods such as slashing and mowing a grass strip between the dwelling and the bush, and removing surface litter.
• Bare earth firebreaks such as strategically placed driveways and footpaths situated across the direction from which the fire is likely to travel, usually from the west.
• Clear gutters of leaves and twigs, and enclose spaces under houses and decking so burning leaves and twigs can't lodge there. House fires most commonly start in the roof or under the house or decking.

Community Fire-Guard
Communities are encouraged to take action to protect themselves. Community Fire-Guard is accessible through the Rural Fire Service and NSW Fire Service and has the following slogan:

Education - Empowerment - Responsibility
Education is to make people aware of the possibility of bushfires, to better understand their nature, and to let them know what they can do. Shire Councils are now required to map bushfire prone areas so that residents and intending purchasers know the risks.
People are empowered by their knowledge to reduce the fire hazards around their houses and communities. Basic firefighting equipment can be supplied to help contain a fire until the brigade arrives. These community groups are not intended to be fire fighting units.
Through knowledge comes a greater involvement and responsibility for preventing and managing fires, for the protection of individual and community property, and for making decisions about whether one really wants to live in a bushfire prone area.

Bushfire Management Plans

The Rural Fire Commissioner will have a bushfire management plan for each region based on geography, vegetation and fire history. This plan will be administered by a regional Bushfire Management Committee which should lead to a more co-ordinated approach to management based on current knowledge about fire control and about the short and long term effects of fire on the environment.
Our natural environment is in grave danger from too frequent bushfires. About seventy percent of fires in National Parks in Christmas 2001 spread into the parks from adjacent lands causing too frequent devastation. We humans are responsible for that, and we must try to do something about it. We must maintain biodiversity to support the right of other organisms on this earth to go on existing and for the future generations of our own kind.

J40 Summer 2002-3