A startling phenomenon occurs after a bushfire tears through a landscape. From the blackened soil springs an extraordinary natural revival – synchronised germination that carpets the landscape in flowers and colour.
So what is it in bushfires that gives plants this kiss of life? The answer is smoke, and it is increasingly transforming everything from large-scale land regeneration to nurseries and home gardening.
Burnt plants survive bushfires in various ways. Some are protected by woody rootstocks and bark-coated stems; others resprout from underground buds. But most plants awaken their soil seed bank, which may have lain dormant for decades, or even a century.
However, this smoke-induced seed germination is not easily replicated by humans trying to grow the plants themselves. Traditionally, many native Australian flora species – from fringe-lilies to flannel flowers and trigger plants – could not be grown easily or at all from seed.
In recent decades this has meant the plants were absent from restoration programs and home gardens, reducing biodiversity.
In 1989, South African botanist and double-PhD Dr Johannes de Lange grappled with a similar conundrum. He was trying to save the critically rare Audonia capitata, which was down to a handful of plants growing around Cape Town. The seed he collected could not be germinated, even after heat and ash treatments from fire. Extinction looked inevitable.
But during a small experimental fire, a wind change enveloped de Langer in thick
smoke. With watering eyes, he realised that smoke might be the mysterious phoenix factor that would coax the seeds to life. By 1990 he had shown puffing smoke onto soil germinated his rare species in astonishing numbers.
The technique is simple. Create a smouldering fire of dry and green leafy material and pass the smoke into an enclosed area where seed has been sown into seed trays or spread as a thin layer. Leave for one hour and water sparingly for ten days to prevent the smoke from washing out of the seed mix. The rest is up to nature.
Soon after the de Lange discovery, I visited the Kirstenbosch National Botanic Garden in Cape Town. I was shown a few trays of seedlings out the back – some from seeds treated with smoke, some without. The difference was stark. Smoke-treated seeds produced a riot of green, compared to others that resulted in sparse, straggling seedlings.
But was smoke just an isolated African phenomenon, I wondered? Would 150 years of frustrated efforts to germinate some of Australia’s most spectacular and colourful species – from grevillea and fan-flowers to rare native heaths – also be transformed by smoke?
At first, the answer appeared to be no, as every attempt with Australian wildflower seed failed. But after many trials, which I oversaw as Director of Science at the Western Australian Botanic Garden, success came in 1993. Extra time in the smoke house and a serendipitous failure in the automated watering system resulted in the germination of 25 different species with seedlings. Some were thought to have never been germinated by humans before, such as wild-picked yellow bells (Geleznowia verrucosa) or the giant feather rush (Loxocarya gigas).
This discovery meant for the first time smoke could be used for difficult-to-germinate species for the home gardener and cut flower growers. These days more than 400 species of native seeds, and potentially more than 1,000, respond to smoke treatment. They include kangaroo paw, cotton-tails, spinifex, native bush food tomatoes and fragrant boronias.
Highway plantings, mine site restoration and, importantly, efforts to save threatened plant species now also benefit greatly from the smoke germination technique. For example, smoke houses are now a regular part of many nurseries, which also purchase smoke water to soak seeds for sowing later.
In mine site restoration, direct application of smoke to seeds dramatically improves germination performance. This translates into multimillion-dollar savings in the cost of seed.
Smoke is also a powerful research tool used to audit native soil seed banks, which includes demonstrating the adverse affects of prescribed burning in winter and spring on native species survival.
Collaboration with research groups in the US, China, Europe and South America has expanded the use of smoke to germinate similarly stubborn seed around the world.
In 2013, an Australian research team made a breakthrough in determining which of the 4,000 chemicals in a puff of smoke resulted in such starting germination. They patented the chemical and published the discovery in the journal Science.
The smoke chemical, part of the butenolide group of molecules, was named karrikinolide, inspired by the local Indigenous Noongar word for smoke, karrik.
Karrikinolide is no shrinking violet of a molecule: just half a teaspoon is enough to germinate a hectare of bushland, which equates to 20 million seeds.
Smoke is sold to home gardeners and for commercial use in the form of smoke water, smoke-impregnated disks, or smoke granules. All contain the magical karrikinolide molecule.
Home gardeners can try smoking their own seeds – but what you burn matters. Wood smoke can be toxic to seeds. Making your own smoke from leafy material and dry straw ensures you have the right combustible materials for germination.
For the home gardener, having a bottle of smoke water on hand or constructing your own smokehouse can make all the difference to germinating many species – including those stubborn parsley seeds. To find out more, a webinar at this link shows you how to use smoke and even construct your own smoke apparatus.
Ten years after the devastation of Black Saturday, building design has largely been unrecognised as an area worthy of research. We have advanced our knowledge of the materials used in the construction of homes in bushfire-prone areas but we continue to use the design model of the suburban home.
This needs to change. An initial starting point is to consider the way previous bushfires have damaged and destroyed buildings.
A bushfire has five different elements: smoke, wind, embers, flames, and radiant heat (the latter two are collectively called the “fire front”).
Smoke and wind are usually present throughout a fire, but are particularly high when the fire burns at its most intense levels. Depending on the type of vegetation burning, isolated flying embers may arrive hours before a fire front. Intense ember attacks usually occur 15-30 minutes before a fire front arrives, and may persist for up to 8 hours after the fire front moves on.
Radiant heat at a level that makes it impossible to survive outside will persist during the passage of the fire front, which may last anywhere between 2 and 15 minutes. However, if consequential fires are ignited by the main fire front, the radiant heat may remain at non-survivable levels for much longer.
The smoke of a bushfire reduces visibility and can turn a bright day into night. A change in wind direction can renew a threat residents thought had already passed them.
Most people would expect that the most destructive element of a bushfire is the fire front, but rather surprisingly that’s not the case. Ember entry and associated spot fires, rather than direct flame contact, accounts for 75-80% of homes destroyed by bushfires.
Embers can be large strips of burning bark, or a tiny spark as small as a pinhead, and depending on wind speed these can travel up to 10 kilometres ahead of the fire front.
Australian research over the past 75 years has revealed more than 20 different parts of a house and its surrounding area that are vulnerable to bushfire attack. Much of this knowledge has now been incorporated into a recently updated Australian Standard: Construction of buildings in bushfire-prone areas.
These guidelines aim to reduce the vulnerability of each part of a house, and thus make the structure as a whole more resistant to bushfire damage. The Standard applies across Australia for new homes and renovations.
The known weak parts of a building are referred to as the “building ignition points”. Several are considered below:
In domestic homes the roof cavity is the large open space under the roof and above the ceiling. Embers in this space can cause fire to spread rapidly, making the whole building vulnerable to ceiling collapse.
Any gap in the roof, such as a poorly secured tile, can allow flying embers to enter. The burning crown of a nearby tree, pushed onto a roof by high-speed winds, can also ignite the house.
When people choose to shelter in their bathrooms they often forget the ceiling is particularly vulnerable there. It’s difficult to access a roof cavity with a fire hose, and extinguishing embers and fire invariably damages electrical wiring, plasterwork, and home contents.
Regular inspection and maintenance of roof elements can help reduce ember entry. Avoiding trees close to your house, and removing any overhanging branches, can also help reduce this bushfire risk.
Overhanging trees can cause compacted leaf litter to build up in gutters. During a bushfire flying embers land in this material, catch alight and spread flames to combustible parts of the roof structure such as wooden facia boards, rafters, roof battens, and eaves.
It’s a good idea to clear out your gutters each year as part of seasonal bushfire preparation. Some people choose to wait until a bushfire is approaching to do this, but going onto your roof for the first time in semi-darknes while embers are flying at you can put you at risk, and endanger your life.
If you’re building a new structure you can consider extending the roof line and having a water collection system on the ground to remove the need for gutters.
Vents and weep holes
Together vents and weep holes allow for fresh air to pass through a building and for excess moisture to leave, reduce condensation and mould. They are necessary for our comfort and health, and maintaining the integrity of a building.
However in a bushfire these types of external openings can allow flying embers to enter the building and start spot fires. Having steel or other non-combustible mesh with small holes in front or behind vents and weep holes can reduce the bushfire risk while still allowing air and moisture to pass through.
Often houses constructed in bushfire-prone areas are built on a sloping block of land. The area under the building (the subfloor) is left open rather than being enclosed, and combustible materials are often stored there. The danger is similar in scale to embers in the roof cavity. When embers or flames take hold in this subfloor area they can spread under the entire building and allow the fire to move up.
Plants and mulched garden beds next to the home
Garden beds and timber steps near a house are a potential danger during a bushfire. Plants with dense foliage can burn intensely and cause radiant heat damage, cracking and imploding nearby windows and glass doors.
Garden beds which have been recently mulched can trap flying embers and spread fire to timber subfloors. It’s much better to have a non-combustible paved area next to your home, with pots containing either succulents or plants with thin foliage.
Deciding whether to stay and defend a home or leave early is a difficult and contentious choice. Hopefully, knowing more about some parts of your house which are most vulnerable to bushfire attack will make that decision easier.
On average, renovating a home generates far more waste than building a new one from scratch.
This waste goes straight to landfill, damaging the environment. It also hurts your budget: first you have to pay for demolition, then the new materials, and then disposal of leftover building products.
By keeping waste in mind from the start and following some simple guidelines, you can reduce the waste created by your home renovation.
Waste is often treated as inevitable, factored into a building budget with no serious attempt to reduce it.
By raising the issue early with your architect, designer or builder, they can make decisions at the design stage that reduce waste later. Often the designers and architects don’t see their decisions contributing to waste – or rather, they don’t really think about it.
During my research on reducing construction waste, I asked one architect what he thought happens to the waste generated. He laughed with a glint in his eyes and said, “I think it disappears into pixie dust!”
One simple early decision that dramatically reduces waste is designing with material sizes in mind. If you have a ceiling height that does not match the plasterboard sheet, you end up with a tiny little strip that has to be cut out of a full sheet. In the case of bricks, not matching the ceiling height is even more wasteful.
Obviously not all materials will work together at their standard sizes (and you need to fit your renovation to the existing house). But sensitive design can make intelligent trade-offs, reducing overall waste.
When I asked architects why they don’t design zero-waste buildings more often, they said clients don’t ask for it. Make it part of your brief, and ask the architect how they can save money by using the materials efficiently.
If you’re using an architect for your renovation, it’s common to have very little collaboration between them and the builder. Any errors or issues are usually spotted after construction has begun, requiring expensive and wasteful rework.
Instead, ask your architect and builder to collaborate on a waste management plan. Such integrated approaches have worked well in Australia and the United States.
This means clients, engineers and builders are collaborating, rather than taking adversarial roles. For such contracts to work, it’s important to involve all parties early in the project, and to encourage cooperation.
The briefing stage is an opportunity for architects, quantity surveyors and builders to work together to identify a waste minimisation target.
One the biggest contributions to waste on sites is late design changes. Client-led design changes are identified in all literature as having far-reaching implications on waste.
These are mostly due to owners changing their mind once something is built. Reworking any part of a building due to design changes can account for as much as 50% of the cost overrun, as well as causing delays and generating waste.
The early work with your design and construction team outlined in the first steps gives you the chance to make sure you’re committed to your original design. Skimping in the planning stage can end up costing you far more in the long run.
Ask your builder not to demolish the building, but to deconstruct it. Deconstruction means taking a building apart and recovering materials for recycling and reuse. This provides opportunities for sorting materials on site.
Salvaged materials can be resold to the community or reused in the renovations. It greatly reduces the tip fees which are usually higher for mixed waste (typical from demolition process) and lower for sorted waste.
Of course this takes more time and has an additional cost. Therefore you do have to balance the cost of deconstruction against the savings.
Denmark, which recycles 86% of its construction waste, has made it mandatory for all government buildings to undergo selective demolition and sorting of construction waste. A good place to start in Australia is your state environment department, which may have guidelines on what is involved.
Good-quality materials last longer, reducing maintenance later. Choosing manufacturers that use minimal packaging also reduces waste (be careful here to check the difference between “minimal” and “inadequate” packaging, as the latter can mean your material breaks).
Reusing materials from your renovation may also be an option (you will need to discuss this with architect and builder at the beginning of the project). Finally, using materials with recycled content is a great option, and boosts our recycling industry.
The return of the breeze block
In March 2017 the Housing Industry Association released data suggesting the Australian residential building industry will increasingly become more dependent on renovation work rather than new construction,
If you’re renovating your home, making efficiency and low waste a priority helps cut costs and reduce landfill.
Australia is a land of extreme weather. Events such as the 2009 Victorian bushfires, the 2011 Queensland floods and Cyclone Yasi in 2013 are stark examples of climate-related risks faced by Australian households. Many homes are built in high-risk locations including floodplains, coastlines and bushfire-prone land.
It also sets out the role of banks and insurers in promoting risk reduction and climate adaptation for Australian housing.
Housing represents many Australians’ biggest financial commitment – including those who rent rather than buy. Housing accounts for up to one-third of the economy, through direct and indirect means and across sectors such as finance, insurance and construction. With population projections forecasting continued growth and attraction to risky locations, banks and other financial institutions have a crucial role to play in minimising the economic threat posed by climate change.
But while the role of land-use planning and insurance with regard to climate risks has been well documented, the role of banks as gatekeepers to housing finance has been largely overlooked.
As the Climate Institute’s report points out, banks have a “unique ability and incentive” to steer housing purchases, because they are the main providers of residential financing. As such, they have large financial liabilities if homes are lost to fires, floods or other climate effects.
There are a range of tactics banks might use to reduce or mitigate climate risk. For instance, they could favour lending on homes that meet specific risk-reduction requirements, such as raised floor levels for homes in flood zones, or fireproof construction materials in bushfire-prone regions. This approach could also be used in setting mortgage insurance premiums as well as the mortgages themselves. Another approach is to better apportion their exposure – by lending on a reduced percentage threshold of the total property value.
If banks continue under a business as usual approach, they face the risk that many properties will be devalued over time, through continued exposure to extreme weather events. This represents a significant financial liability, especially when you consider that a home loan typically takes 30 years to play out – a similar time scale to the many climate impacts expected for Australia.
Banks are already making moves to restrict lending based on location.
But the report outlines several other things banks could do, such as:
examine climate risk exposure in their current lending practices
use their role as financiers to support good policy, by engaging policymakers and financial regulators
encourage stakeholders, including the public, private sector and civil society sectors, to develop ways to minimise climate impact risks for housing
ensure losses are addressed in an equitable way.
The report also details how the insurance sector assesses risk to housing, and how it might improve its approach in the future, given the intersection of urbanisation, population trends and the trend towards living in climate-threatened areas.
The insurance sector has historically been seen as the messenger of housing market signals, because of its keen focus on assessing weather-related risk. But the 2011 Queensland floods highlighted many weaknesses in relying on insurance alone.
Many properties did not have adequate flood insurance, leaving many people without a home after losing their house to the floods. The Australian and Queensland governments and the private sector struggled to co-ordinate a cost-effective response, partly because of previous bad land-use planning decisions, but also because of the lack of adequate insurance cover.
Critically, gaps identified in building codes, land use and climate resilience still require a more co-ordinated response. The current Stage 2 coastal law reforms in New South Wales offer a potential example of how competing interests might be balanced.
At face value, this issue is a no-brainer. After all, risk mitigation is bread and butter for lending institutions and insurers, and we already know that extreme weather events are forecast to increase in frequency and severity. National resilience is required.
Quantifying this risk will be easier if financial institutions utilise access to relevant data on issues like coastal risk. Some of these data are becoming more freely available. Recognising the value of climate data is a trend that should continue. For a robust and resilient future, governments and the private sector should end their tango over who should pay for the information and agree that financial climate risks are best faced with eyes wide open.
The link below is to an article reporting on an approval for a mine in the Tarkine region of Tasmania, home to the endangered Tasmanian Devil.