Bushfire recovery

Much of the Australian flora is very resilient to fire and adapted to recover from fire events. Where the fire has been of a lower temperature it can be expected that the recovery will be relatively swift depending on rainfall. Groups of plants like Eucalypts are adapted to fire with buds under protective bark to produce foliage relatively quickly, seed of wattles (Acacia) and Banksias are stimulated to germinate by fire – similar adaptations occur in many of the species in our woodlands and heathlands.

If the fire is too hot then there is almost a sterilisation effect with very low recovery -we may see a mosaic of effects across the landscape. For ecosystems like rainforests which have burnt where the species and communities are not fire-adapted, the recovery, if it happens at all, will be very long term.

It is difficult to estimate the number of plants impacted by the fires. Published tree densities in different ecosystems range from 500 – 1,200 trees per hectare and if we multiply this by the area burnt (10 million hectares and counting) with an assumption that 60% was natural ecosystems this could give 3 – 7.2 billion trees impacted; with as many understorey species affected. The impact on understorey species is usually much more dramatic, and final, as these species are more likely to be burnt completely.

However, the answer to this question is much more nuanced. The flora of Australia has evolved with fire – as the continent has moved north and become more arid, species like Eucalypts and wattles have come to predominate.

These plants have numerous adaptations to cope with fire – in Eucalypts epicormic buds protected by bark spring to life after a fire with amazing haste – and seed of wattles and Banksia are stimulated to germinate and grow once it rains enough to allow successful establishment. In some cases we may even see species of plants grow that have not been observed for a long time. 

The extent of recovery will depend on the intensity of the fire – lower intensity fires do not substantially damage Eucalypts and will stimulate germination of seed of a range of species.  If the fire is high intensity, we see trees killed and an almost sterilisation of the forest floor. In these situations, the loss of plant diversity may well be profound.

In ecosystems that are not adapted to fire the losses can be much higher.
Rainforests have not evolved to cope with dry conditions or fire. The trees in these forests are often thin-barked and easily killed by the heat of bushfires and when these habitats burn the outcome is poor.

The impact of fire on threatened species of plants will be variable – it will depend on the distribution and intensity of fire and local conditions. It will take a long time to assess the situation across ecological communities around the country. Monitoring the impacts and responses will be critical.

Fire impacts different communities in different ways. Some communities such as heath and Eucalypt woodland are adapted to fire and recover quickly from them and this will be seen soon after the event, given favourable conditions such as rain, with resprouting and seeds germinating. Communities in colder, dryer and more exposed areas will respond more slowly than communities in warmer and wetter areas.

A very intense fire may kill normally resistant species and/or alter the structure of a community significantly so that the species structure in an area after a fire may be quite different to that that existed before a fire.

Other communities are not tolerant of fires and the species found in them will not regenerate after fire. Communities such as rainforest and sphagnum bogs, if burnt, can take 100’s of years to recover if they do at all. In some cases, these communities will be lost and replaced with a different community.
 

The rainforest areas in the Nightcap NP, at the border between NSW and QLD, are of great concern. Our research suggests that these are amongst the more diverse forests in Australia (sometimes including up to 100 TREE species per 1000m2), with high proportions of ancient, endemic lineages that go back to Gondwanan times.

Potentially 30 or so rare tree species and similar numbers of rare animals are likely to have been impacted by the fires, directly and indirectly (through significant changes in habitat). Interestingly, the reason why these rainforests are so diverse and these rare species survived only here, is because they have been protected from major fires for a very long time.

Many rainforest trees have thin bark that does not provide protection against fire, and even after a relatively low-intensity litter fire the bark can crack and eventually lead to complications (some plants can die months after the fire).

Yet rainforest vegetation itself can provide protection against fires and slow them down. Historically these core centres of endemism have been protected by the size and mass of rainforest vegetation present.

Unfortunately, the historical legacy of fragmentation for development and increasing presence of eucalypts and associated vegetation within this new forest matrix, has made these core rainforest areas much more vulnerable to exceptional events such as the ones we are currently witnessing.

For some species the recovery period might appear short with green foliage happening very quickly, but other species will take much longer. If there is sustainable rain next spring and summer may be quite productive for many species with good flowering events and subsequent seed productions, for other species this may occur in subsequent seasons. For other slow growing species the recovery period will be years or even decades.

Certainly for many species it will be important that there is a significant gap before a subsequent fire event as the frequency of burns, where they are too close together, can have a very detrimental effect on their long term survival.
 

The response of plants from the combined impact of drought and fire will depend on good rainfall. If good rainfall occurs we can expect rapid recovery from ‘resprouters’ such as native grasses during the first year, and even some seed production.

Other species will be slower to resprout or rely on seeds held in the soil to germinate and grow. With reasonable rainfall we anticipate a good ‘three year window’ where seed of fire responsive plants will thrive and potentially produce large amounts of seed in the altered post-fire landscape.
 

The areas that were burnt cover a very large area that contain a multitude of ecological communities and 100’s of threatened species. The distribution of many threatened species are found entirely or largely in the burnt areas. Threatened plant species are diverse - some species are large trees while others are shrubs, epiphytes, delicate herbs and even algae and mushrooms.

They exhibit a wide range of strategies to deal with fire - some a resistant and will resprout after being burnt, while others will be killed outright and rely on seed or spores for regeneration. The fires have also significantly impacted many other species that had not been considered to be threatened until now but will now possibly warrant formal listing.

The full impact of the fires will be unknown for some time and survey work is required to assess the impact of the fires on each species. Some species will be lost or have had their populations severely reduced, while others will recover. These species will need to be monitored over several years to ensure their survival.

Yes we will. Species with bulbs, such as ground orchids, may be present in a community but are sometimes rarely seen as they are hidden by the vegetation. These species are more obvious after a fire has removed the ground cover. Some ground orchids, such as Pyrorchis nigricans (Red Fire Orchid) and Burnettia cuneata (Lizard Orchid), do respond to fires with profuse flowering the following season. 

Many species require fire to regenerate and may exist for years as seed in the soil without being obvious above ground. The heat and chemical triggers required for germination are sometimes only provided by fire and after a fire a mass germination occurs.

This is common in the family Rutaceae (includes Boronia and Correa) for example. Other species fruit open only after a fire has passed through the area, for example this occurs with many species of Eucalyptus, Banksia and Hakea, and so seedlings of these plants are often only seen after a fire.
 

Weedy species are well adapted to colonise burnt areas and so in many burnt areas weed species could become more prevalent and out compete native species.
 

There is no evidence to indicate bushfires kill or eliminate Phytophthora in natural ecosystems and some evidence to indicate that these organisms survive. The loss of ground cover vegetation and shrubs leads to greater surface and subsurface run-off in post-fire rain events which may in turn exacerbate the spread of soil borne pathogens such as Phytophthora.

Myrtle rust on the other hand can be killed by the intense heat and fire, but the prolific new growth of post-fire regeneration provides abundant highly vulnerable young tissue for new infections if weather conditions favour infection.

Insect pests, except for some larval stages that are buried underground, are generally wiped out in bushfires. It is likely that very large numbers of invertebrates will have killed in the fires.
 

The most critical thing trees, and other plants, do is store carbon – taking in carbon dioxide during the photosynthetic process and expelling oxygen for us and all other organisms to breathe. They provide habitat for other organisms, especially wildlife. Plants are essential for life.

Firstly, have any large damaged trees inspected by an arborist to determine if there are any safety/structural issues.

The important thing in garden areas is to maintain good watering and be patient - resisting the temptation to drastically prune dead leaves and branches on shrubs and trees, as this will be protecting the live (regenerative) tissue from summer sun damage. Observe regeneration and resprouting and let this guide your pruning and shaping of plants.

For bushland areas keep an eye out for resprouting plants and native seedlings that will emerge from the ash bed. This a good time to control weeds, which will also take advantage of the post-fire conditions.

Assessing the post-fire landscape is also a good time to consider vegetation setbacks and an opportunity to redesign parts of your garden. In a garden redesign it is worthwhile considering low flammability species such as hardy rainforest trees/shrubs, saltbushes and evergreen trees.
 

All of the Garden's scientific facilities, programs and living collections across all botanic gardens in Sydney are being united under the new Australian Institute of Botanical Science.

The Institute will be the nation’s premier botanical research organisation, advancing fundamental knowledge of flora and driving effective conservation to ensure the survival of plants, and all life that depends on them. 
 

The Australian PlantBank came into existence as a direct result of the need to protect our flora from a multitude of threats that have been escalating in recent times. Climate change is a major threat as all plants have limits of temperature and available moisture within which they can survive. Hotter, drier conditions could lead to extinctions and, of course, can lead to fires, which are now on an unprecedented scale.

Other threats include diseases like Myrtle Rust which only entered the country ten years ago, but has put several once common species on the brink. Many species face more than one threat. PlantBank scientists study which are the most at-risk species, and work on solutions to help conserve them. Importantly, PlantBank houses significant seed collections of Australian species. The seed vault hold seeds of over 5000 species and 61% of NSW threatened plant species. This collection, along with the tissue cultures and living plant collections of our gardens, safeguards against extinction following catastrophic events.
 

We will be closely monitoring populations of plants, especially threatened species, to assess there recovery and to take opportunity to collect seed for the seed bank and other purposes. It is clear we will need resource to ramp up these programs to meet the urgent need to ensure plants are conserved and not threatened by extinction.

The Gardens, working closely with Government and other institutions, will continue and expand its work on threatened species. This research will include assessing existing knowledge, conducting field research and surveys both within and without of the burnt areas, continue and set up ne long-term monitoring projects, document biodiversity and how it affected by the fires, collect seed and provide seed stored in the seedbank for some species to aid in research, propagation and translocation of some species. The Herbarium collection and the data associated with it will play a critical role in this by providing base data for most species and being the repository of new collections and data made through this research.
 

Our collections at the National Herbarium of NSW are an unparalleled receptacle of cumulative flora data, and largely constitutes a permanent and often well-documented record of the distribution of predominantly NSW flora through time.

In the short to medium term post fires, this data can be used for obtaining information about the composition, distribution and content of plant diversity in a given region (bolstered by the current onset of botanical information through our digitalisation), and ultimately assists with restoration and conservation.

Longer term, the data can be used to populate species distribution models that predict changes in geographic ranges, diversity and composition of species under scenarios of future climate.
 

If we have collected them and they are in the seed bank or garden yes we can restore them back into the natural environment. It is a slow process and requires considerable resources. We work with a range of partners across Australia and internationally to ensure the most effective and efficient use of resources and maximise the likelihood of success.
 

The vegetation surrounding Sydney is amongst the most diverse in Australia, with the Blue Mountains being listed as World Heritage Area because of the diversity of its flora (in particular of Eucalyptus species) and its high levels of endemism. Our studies have repeatedly shown the evolutionary richness of these sandstone vegetation types, which include many rare species of plants and animals. Most of this vegetation is adapted to fire however, and under normal circumstances has potential to recover relatively quickly.

Of the three Botanic Gardens in our organisation only the Blue Mountains Botanic Garden Mount Tomah has been directly impacted by fire. Approximately a quarter of the Garden has been burnt and 180 hectares of conservation forest surrounding the Garden has also been burnt.

Some parts of the collection at the Garden have been destroyed including the conifer collection and North American woodland collection. The rest of the Garden is relatively unaffected. 

Our other Gardens, Royal Botanic Garden Sydney and Australian Botanic Garden Mount Annan have not been directly impacted by fire.