bushfire, climate change, design, ecology, erosion, farm, fire, Fleurieu, Fleurieu Coast, permaculture, planning, resilience, revegetation, seasons, soil, summer, trees, zones
A few evenings ago, someone set off fireworks on the road beside our property. Embers from the fireworks landed in the grass on the property boundary and quickly took, spreading through the dry summer grass along the fence and down a drainage line. Thankfully, our neighbours quickly noticed and set to work with their own fire unit while awaiting the arrival of the police and Country Fire Service. The blaze was contained with minimal damage, but it’s stimulated us to revisit our property plans and consider how we’re designing for the inevitability of fire.
The 2018 State of the Climate report, prepared by the Commonwealth Bureau of Meteorology notes disturbing climatic trends, including:
- Warming of Australia’s climate by 1 degree since 1910, increasing frequency of extreme heat events.
- Decline of April-October rainfall by about 11 percent in southeastern Australia since the late 1990s.
- Long-term increase in extreme fire weather and the length of the fire season across large parts of Australia.
Likewise, the South Australian Government’s environmental trend and condition report cards confirm worrying trends, with current and projected temperature and rainfall trends rated as “Getting Worse”. Winter rainfall, the main season for rainfall in the state’s Mediterranean climates, has declined 10-40mm per decade since 1990, a significant decrease in regions where the total annual rainfall may only be 300-500mm. In the southern parts of the state, the climate has warmed by almost 1 degree Celsius, with a substantial increase in days over 40 degrees Celsius.
The decline in rainfall is evident in the rainfall trends from local weather stations. We calculated trends from 5-year averages of our local stations’ rainfall and noted declines in two out of three of the nearest weather stations with data going back to the 1800s. Our nearest station, Poolamacca, showed the steepest decline, followed by Yankalilla, with Normanville showing a slight upward trend, although it is missing a number of years of data. In a hotter and drier climate and ecosystems evolved for fire, bushfires are not a matter of “if”, but “when”.
This presents a design dilemma. For an open grassland, subject to constant driving winds and solar exposure, designing for shade and shelter is essential. The creation of microclimates supports not only human comfort, but also creates a mosaic of habitats for the cultivation of different plants and animals as well as supporting the cycling of moisture. We’ve planted trees for timber, firewood, windbreaks, erosion control, habitat and food and these remain priorities for the property, but in line with many permaculture approaches, they also increase the biomass – or fuel – available. Likewise, as we explore more managed approaches to grazing, we hope to increase the health of the soil and pasture. Good grazing practice and approaches to cultivating soil biology also suggest the maintenance of a high level of ground cover to protect soil life through the dry season while also increasing soil water retention. So here’s the challenge: in a hotter, drier climate, it’s essential to design for shelter and shade, to harvest water and nutrients in the soil and cycle it locally through vegetation but these aspirations can also increase the risk of catastrophic fire by increasing fuel load. As Andrew Millison writes in Permaculture Design Tools for Climate Resilience, “Fire is especially risky in permaculture systems where planting trees, increased biomass, and increased vegetative coverage are goals. Integration of water storage in the landscape becomes an important balancing point to the increase in biomass and fuel load. Also, the planting pattern of agroforestry and perennial systems is important in its consideration of how fire will move through that landscape.” It’s a high-stakes design challenge, and one that we do not claim to have any answers to. However, here’s a few things we’ve thought about.
First of all, the Country Fire Service has some advice for bushfire safety, including:
- Ensure 20 metre fuel breaks around homes
- Mown lawns, wide paths and vegetable gardens are most suitable in the area closest to the home
- Maintain 5 metre fuel breaks around sheds and along fence lines
While at this stage we’re still considering overall property planning rather than the specifics of house design, the CFS also advises that when considering siting of homes or other infrastructure:
- North and west facing slopes hold a greater fire risk due to solar exposure
- Fire travels quickly uphill, with speed doubling for every 10 degree increase in slope
- Tracks and gates should be designed for emergency services access with gates at least 4 metres wide, no gradient greater than 1:3, compacted roadways, solid creek crossings and a minimum 25 metre diameter turn-around area.
In the spirit of a classic permaculture “sector analysis”, in our context, and for many rural properties, the public road is a likely point of origin for fires with grass fires regularly started by passing motorists flicking cigarettes out the window, cars catching on fire, fuel spills, or other means. This is exacerbated for us by prevailing summer winds that blow any fires at the road towards our property, beginning on the dry and exposed northwestern slopes at our road boundary.
Our strategy is to design for multiple waves of fire breaks that also serve other design functions across the property such as providing access, grazing, shelter or other functions. Andrew Millison writes that “fire breaks consist of any design element that will not carry fire through the landscape. Some examples are roads, irrigated gardens, crop fields, irrigated orchards, recreational lawns, concrete slabs, animal grazing areas, ponds, wetlands, greywater systems, and closed canopy hardwood forests comprised of fire resistant species.”
In our planning we also need to consider how and when to isolate elements from each other and when to connect them through corridors. For habitat purposes, it’s important to build connections, and continuity is also important for wind protection, however we also need to ensure we’re avoiding creating any corridors for fire to move easily through the property. One of the first elements of our design was to establish “wilderness” areas composed of mostly locally indigenous revegetation around areas of historic erosion. These areas have been designed to support habitat but are not designed for fire-resistance. While we conduct fuel reduction in these areas through mowing, these are areas we need to be conscious of isolating from obvious fire pathways, due to the species present, but also because of the difficult access amid erosion gullies and sinkholes.
In his Introduction to Permaculture, Bill Mollison describes some strategies for managing fire risk:
- Reducing fuel in the fire sector through managing forest floor (clearing litter and fallen timber), mowing or grazing, and creating “non-fuel surfaces” such as roads, dams, sheet mulch and green crops.
- Creating barriers to reduce radiant heat that can be structural (such as ponds, earthbanks or stone walls), or plantings of fire-retardant species (Mollison suggests lilies, coprosmas or willows).
- Planting windbreaks of fire-retardant species to reduce wind during fire.
According to Mollison, fire-resistant species have several characteristics:
- High water content
- High ash content
- Minimal mulch or litter drop, or quickly-decomposing litter
- Fleshy or sappy.
Mollison recommends figs, willows, mulberries, Coprosma, and some acacias (Acacia dealbata, A. decurrens, A. saligna, A. sophorae and A. baileyana) as fire resistant trees and also provides a list of some appropriate ground covers as well. Mollison goes into further detail in Permaculture: A Designer’s Manual, suggesting “wildfire will always happen, often every 8-30 years, on many sites. It will not be severe if normal annual fuel reduction is practiced.” This highlights that any design must also be maintained through meticulous management.
Agroforestry advocate Rowan Reid also has some insights regarding the interaction between trees and fire. In his article Trees and Fire Reid observes that there is little landholders can do to impact temperature or humidity, but they can change wind speed through strategic windbreak plantings, which, depending on conditions, could also potentially reduce fire spread and intensity.
Reid goes on to consider the impact of the fuel provided by particular trees, observing that “fine fuels” such as grass, leaves or bark dry out as the fire approaches and burn quickly. Property designers must therefore consider how they break up continuous swathes of fine fuels to avoid the rapid spread of fire. Likewise, some trees contain volatile oils increasing their flammability. Reid offers a set of criteria for considering species suitability to fire resistance:
- Tight, clean bark that sheds in small pieces to avoid fire ladders that carry ground fires up into the canopy
- Leaf shape, moisture and oil content (“Wattles are better than any of the eucalypts or tea-trees, but then the oaks and elms are fantastic.”)
- Retention of dead leaves or branches through the dry season
- Effect on the vigour of groundcover. If a tree has appropriate bark and oil content and also reduces groundcover directly underneath through shading or moisture competition then Reid says this can create “a very effective firebreak”. Bared ground can increase vulnerability to soil erosion however.
According to Reid, well-managed deciduous trees, pruned high with the groundcover managed through grazing should create “an effective fire break and radiant shield.” This limits the potential for fire to move from ground to canopy and ideally the plantings themselves would deflect wind and trap embers. Reid concludes that “clearing might make you feel safer, but in the event of a wildfire it might only improve the view of the fire as it comes hurtling towards you.” Reid’s approach highlights the necessity of continued, thoughtful management of the landscape as well for both timber quality, tree health and fire resistance. For us, this needs to happen both through diligent maintenance, but also considering how we manage grazing. This will include planning grazing to reduce fuel in high-risk and high-value areas and reserve feed in lower risk fire areas for later in the season.
We have a well-thumbed and much-loved copy of Farmtree$ for the Mount Lofty Ranges: A Regional Agroforestry Handbook which helpfully contains lists of tree species for fire-retardant shelterbelts as well as species which bare the soil to reduce fuel load. We have tried to include some of these in our existing plantings and plans, and will return to this list again in refining our design.
Some fire-retardant or fire-reduction species we’ve tried so far:
Acacia melanoxylon (Blackwood) – a native timber species typically associated with higher rainfall areas, we’ve found this takes well in some of our loamier, well-drained soils. We’ve planted this throughout our revegetation zones but probably wouldn’t scale up with woodlots given that it is already marginal in our climate and will become more so with a hotter, drier climate. Blackwood is considered a fire-retardant species in Farmtree$ for the Mount Lofty Ranges.
Acacia pendula (Weeping myall) – we originally interplanted this as a summer fodder species with Old Man Saltbush (Atriplex nummularia) after we read somewhere that it didn’t mind grey cracking clay. It’s proven to be a slow but steady grower as a shelter species. It can also be cut for firewood or milled for specialty timber or fenceposts. Weeping myall is considered a fire-retardant species in Farmtree$ for the Mount Lofty Ranges. Incidentally, Atriplex nummularia and Atriplex semibaccata, two saltbushes we’ve planted with great success are both considered fire-resistant plants by the Australian Plants Society.
Casuarina cunninghamiana (River oak) – produces quality timber and firewood under the right conditions. We had high hopes for this tree and chose an area that appeared fertile on the edge of a drainage line. We began with an experimental woodlot of fifty trees and they survived, but over several years didn’t seem to grow. At all. These plantings were in the area recently torched so this is an opportunity for us to try a different species. This species is listed as “fire-retardant” in Farmtree$ for the Mount Lofty Ranges.
Ceratonia siliqua (Carob) – We’ve planted this as a fire retardant screen on the ridgeline near our shed. It’s slow growing but there are well established specimens at the nearby Anacotilla homestead and elsewhere in the area which shows promise. Carob is considered a fire-retardant species, and also produces pods that are edible for both humans and livestock.
Eucalyptus cladocalyx (Sugar gum) – smooth barked, bares the soil reducing ground cover, relatively fast-growing timber species that is also useful for honey production. These are now growing well on a grey cracking clay rise, supported by mulching on contour to gather moisture. They are eucalypts, so still flammable so have been planted cautiously and at a distance from buildings.
Eucalyptus occidentalis (Flat-topped yate) – produces hard and strong firewood, grows rapidly and bares the soil reducing ground cover. We read that this was well adapted to grey cracking clays and has proven itself a vigorous grower under dry and exposed conditions. Like the sugar gum we’ve planted cautiously and at a distance from critical areas.
Ficus carica (Fig) – Colossal old figs are still present around the original Anacotilla homestead in the Anacotilla river valley nearby, and their progeny seed readily all over our farm. We have a few wild figs that have come up by themselves conveniently along fencelines and we’ve also planted our own cultivated variety which is growing enthusiastically. We’re looking to expand our plantings of figs because they appear well-adapted to the climate and landscape, because we like eating them, and because Mollison reckoned they were fire-resistant.
Melaleuca lanceolata (Dryland tea-tree) – we’ve propagated and planted this locally indigenous melaleuca throughout our revegetation areas. It’s relatively slow growing and regularly flogged by grazing kangaroos, however there are some extant specimens visible on some of the surrounding ridges. This species is listed as “fire-retardant” in Farmtree$ for the Mount Lofty Ranges and we’ll continue planting in revegetation areas.
Some fire-retardant or fire-reduction species we’re considering in the future:
Eucalyptus brockwayi (Dundas mahogany) – according to Farmtree$ for the Mount Lofty Ranges this species bares the soil underneath the canopy, reducing fuel load. This however, exposes the soil to erosion and presumably impacts on soil life. However, hailing from clay-loams near Norseman, WA, it’s used to a much more arid conditions than what we currently experience and so may thrive with minimal intervention. Historically it’s been used for tool handles and mine-shaft shoring, and also offers a forage source for honey production.
Eucalyptus sideroxylon (Red ironbark) – another soil-baring species suitable for timber production, however the deeply fissured bark and, like all eucalypts, the volatile oils present in the leaves make it a species to use with caution.
Morus sp. (Mulberries) – identified by Mollison as a “fire-resistant species”, we’re keen to get some mulberries in the ground as part of our experimental dryland fruit tree plantings. The presence of some vast early colonial “Old English” mulberry trees at Rapid Bay, Wattle Flat and near the ruined homestead at the Wirrina Cove Holiday Park just beyond our back boundary offer promise for growing mulberries in our climate and soil. They’re generous shade-trees and offer punnet-loads of delectable berries.
Quercus ilex (Holm oak) – a fire-retardant Mediterranean species, often associated with the famous Spanish dehesa silvopasture system. The Holm oak grows to a substantial size on a rainfall of around 440mm (we’re currently around 600mm), and offers acorns traditionally fed to livestock but also considered to be the most palatable to humans of the European oaks. (This document from the Maltese Planning Authority actually lists Quercus ilex as flammable in contradiction to Farmtree$ for the Mount Lofty Ranges. It does offer a range of other options however, including the locally prolific Desert Ash (Fraxinus angustifolia), Quince and others).
As we work to design our property for climate resilience, planning for fire is an essential element. It requires the considered use of vegetation to create shelter and to break continuity of fuel, together with ongoing and diligent management such as through grazing and pruning to minimise fuel load. We’d welcome any suggestions or thoughts you have as we continue to refine our design.
Fire resistant and retardant plants, Australian Plants Society (Victoria)
Balingup Small Tree Farm in Western Australia offers a range of fire retardant trees for sale and has some interesting reflections on their impact in recent fires in the area.
The worst possible time of year happens to be when everyone wants to set off fireworks. We often have people setting them off here in the North Eastern suburbs of Adelaide too, and there’s so much dry bushland surrounding us. I’m glad your neighbours saw the fire in plenty of time and wish you a safe summer.
Thanks so much, and the same to you! We’re thankful it wasn’t worse and we can use it as an opportunity to refine our property’s design for fire. Stay cool!
Wow your research and knowledge is so impressive. Interesting how misfortune can lead to something different and maybe better. So good that your neighbours were so proactive.
Thanks so much, there’s still much to learn! We’re deeply grateful for good neighbours and a supportive community!
Anthony Waite said:
What value community? Never ending I would think. Congrats to you for building the community around you which in essence is why your neighbours responded in the way they did.