Background

The extensive fires in south-eastern Australia in 2019/2020 burnt many plant species (and their habitats) that were not considered threatened at the time, but had the potential to increase the risk of these species declining to the point of becoming threatened in the near future.

Many factors determined the ability of plant species to successfully recover after the fires, including fire severity, fire frequency, drought and a changing climate, along with impacts of post-fire grazing by feral animals and stock, weed invasions, and pathogens. The International Union on the
Conservation of Nature (IUCN) Red List criteria for species identify different mechanisms by which species may be threatened with extinction. For plants, most are listed as threatened via IUCN Criterion B (i.e. restricted geographic ranges, continuing decline) (Le Breton et al. 2019) in part because data on species distributions is readily available to estimate the likely threshold of risk. To be considered threatened under Criterion B, a species needs also to have demonstrated continuing decline, and one of three co-conditions: severe fragmentation, a limited number of locations (sensu IUCN 2022) or extreme fluctuations.

In 2020, the San Diego Zoo Wildlife Alliance (SDZWA) Plant Conservation Team provided funding to the ANPC to support plant conservation actions (aligned with the recommendations of the Federal Threatened Species Scientific Committee (TSSC) for Post-fire Recovery), to meet the aims of:

1. Supporting the nomination and listing of fire as a Key Threatening Process under Australia’s Environment Protection and Biodiversity Conservation Act (EPBC Act) as well as researching how to reduce the impacts from future fires.

2. Preventing extinction and limiting decline of native species and ecosystems affected by the 2019-2020 fires, through investigating the:

a) impacts of the fires on selected priority plant species with restricted geographic range sizes and the factors threatening their recovery.

b) the complexity of recovery in relation to other known threats, e.g. Myrtle Rust.

Progress to date

1. The SDZWA funding (in combination with other funding sources) has enabled the nomination of ‘Fire regimes that cause biodiversity decline’ as a Key Threatening Process (KTP) under the national Environment Protection and Biodiversity Conservation Act (EPBC Act), through supporting the assessment and preparation process, in collaboration with experts from the national Threatened Species Scientific Committee (TSSC). In April 2022, the nomination was accepted and the KTP was formally listed.

This component of the project, which is now complete, has also helped to develop guidance on recovery actions to build the resilience of biota to future fires, through lead authorship of a major technical report (Department of Agriculture, Water and the Environment, 2022), two chapters in Australia’s megafires: Biodiversity impacts and lessons learned from 2019-2020 (Gallagher et al. 2023 and Lindenmayer et al. 2023), and the publishing of five journal papers: Zylstra (2021); Zylstra et al. (2022), Zylstra (2022), Zylstra (2023) and Zylstra (2024). These papers are aimed at building the human contribution to the resilience of biota to future fires by quantifying the mechanisms of risk and investigating new approaches to reduce the incidence of future fires.

(a)    (b)
Understorey dynamics in Jarrah forest exemplify the drivers of fire risk measured in Zylstra et al. (2022). Recently burned Jarrah (a) has a dense understorey of germinated shrubs and saplings that burned seven times more frequently than the same forest left unburnt for around 50 years, which develops an open understorey (b). Processes of growth and forest succession such as self-thinning and self-pruning act as ‘ecological controls’ on wildfire spread and severity (Zylstra et al. (2022a). Photos: Philip Zylstra

2.a) Gallagher (2020), Gallagher et al. (2021, 2022, 2023) and Auld et al. (2020) identified plant species of national significance in Australia that were potentially adversely impacted by the 2019/2020 fires, using the methodology developed in Auld et al. (2022). Gallagher et al. (2018) and Le Breton et al. (2019) identified those not currently recognised as threatened, that had geographic range sizes that were below the thresholds in IUCN Red List Criterion B. Combining these sources allowed the creation of a priority list of species for field inspections, surveys and extinction risk assessments.

Two groups of taxa were chosen:

Banksia paludosa subsp astrolux was one of the target species surveyed by the ANPC following the 2019/2020 bushfires and is now listed as Critically Endangered. Photo: Tony Auld

i) Species which allowed comparisons of those with canopy versus soil seed banks and also between resprouting versus obligate seeding plants. Obligate seeding species (i.e. those killed by fire) with canopy seed banks are thought to be most at risk from high frequency fire or loss of recruitment following the 2019/2020 fires, as the seed bank is exhausted in a single recruitment event after a fire. Obligate seeding species with soil seed banks are somewhat at risk as the seed bank declines, but some seed bank buffer may remain. Resprouting species are considered likely to be less at risk unless drought conditions led to increased plant mortality before, during and after the fires. In collaboration with the NSW Department of Climate Change, Energy, the Environment and Water (DCCEEW), the University of NSW (UNSW) and Western Sydney University (WSU), the ANPC has been undertaking surveys and working on IUCN Red List assessments and Conservation Assessments for 13 NSW endemics with a narrow geographic range, as NSW was the part of Australia most impacted by the fires. Key summaries of the work are presented in Le Breton et al. (2023). Eight finalised assessments have been completed to date for:

• • • Banksia penicillata, a fire sensitive shrub species with seeds held in woody fruits in the canopy. A number of population declines from the 2019/2020 fires were identified in areas that had not recovered from previous fire (none of the seedlings from a 2013 fire had matured and produced woody fruits when they were killed by the 2019/2020 fires). Recommended for listing under the EPBC Act and declared as Endangered on 4 September 2024.
    • Banksia paludosa subsp. astrolux, a fire sensitive shrub species with seeds held in woody fruits in the canopy. Showed decline in some sites due to very low post-fire recruitment levels. Recommended for listing and declared as Critically Endangered on 4 September 2024.
    • Bursaria calcicola, a resprouting shrub species. One population in seven patches. 50-90% of plants burnt in 2019-2020 fires, low mortality, resprouting but no recruitment observed. Fire facilitated severe weed encroachment in burnt areas, dominant vegetation in some places. Recommended for listing as Critically Endangered.
    • Darwinia fascicularis subsp. oligantha, a fire-sensitive shrub species with a soil seed bank. Not considered to be threatened.
    • Dillwynia crispii, a fire-sensitive shrub species with a soil seed bank. Not considered to be threatened.
    • Grevillea buxifolia subsp. ecorniculata, a fire-sensitive shrub species with a soil seed bank. Recommended for listing as Endangered.
    • Hakea macrorrhyncha, a fire sensitive shrub species with seeds held in woody fruits in the canopy. Recommended for listing and declared as Endangered on 15 November 2023.
    • Leptospermum spectabile, a shrub whose fire response is unknown. Data deficient. More survey work is required to assess if the species is threatened or not.

Future work: IUCN Red List assessments will be undertaken on the five remaining shrub species: Dillwynia stipulifera, Hakea constablei, Leptospermum macrocarpum, Leptospermum rotundifolium and Melaleuca capitata.

Plectorrhiza purpurata growing in Cottan-Bimbang National Park. Credit: Lachlan Copeland

ii) Epiphytic orchids, which were difficult to effectively assess because data on species distributions and populations were limited, as was understanding of their ecology and in particular response to fire. In addition, some epiphytic orchids are affected by taxonomic uncertainty, particularly issues in species delimitation. These factors together are likely to have contributed to the scarcity of extinction risk assessments for these species. Consequently, a group of these orchids was chosen to examine the impact of the 2019/2020 fires on plant survival. These orchids occur on rocks and/or trees and, depending on local fire severity, may escape being burnt, or be scorched and survive, or may be killed. The 2019/20 fires were thought to have hit many of these species particularly hard because they are killed by intense fire, due to a lack of both a (protected) underground dormant phase (which is found in many Australian terrestrial orchids) and/or a persistent seed bank from which to recover. Surveys of four epiphytic orchid species in north-eastern NSW were completed in May 2023 for:

• • • Plectorrhiza purpurata.
    • Sarcochilus aequalis.
    • Tropilis angusta (syn. Dendrobium aemulum sens.lat.).
    • Adelopetalum argyropum (syn. Bulbophyllum argyropus).

The surveys focused on populations which were within areas affected by the 2019/2020 fires and the number of individuals remaining, if any, were counted. The surveys aimed to document the impact of the fires, establish the geographic distribution and population size of the remaining populations, and inform conservation assessment and threatened species listing. This included the collection of data and plant material to assist with taxonomic research.

Many populations were found to be heavily impacted, with most host plants dead and all epiphytes killed. All four species were found to likely meet the thresholds for listing as Endangered according to the IUCN Red List criteria. Conservation assessments are currently underway.

Dr Jeremy Bruhl (University of New England & JJ Botanics, who coordinated the surveys) and Dr Heidi Zimmer (Centre for Australian National Biodiversity Research) gave a presentation on the survey outcomes at the ANPC’s Flora After Fire symposium in August 2023, which can be viewed below.

The field work undertaken by this project has also supported the taxonomic assessment and phylogenetic splitting of Adelopetalum argyropus. New CSIRO research published in Phytotaxa investigating the Adelopetalum argyropus species complex has described 2 new species of orchid: A. howense and A. continentale (now the one in northern NSW).

Read more at this CSIRO blog post describing the research, which was also conducted on Lord Howe and Norfolk Islands, with A. howense and A. argyropus described on those 2 islands respectively.

The full article describes the history of the taxonomy, as well as each of the species and their extent.

Future work: Surveys and IUCN Red List assessments will be undertaken on other epiphytic orchid species such as:

• • • Australorchis schneiderae (syn. Dendrobium schneiderae).
    • Dockrillia mortii (syn. Dendrobium mortii).
    • Dockrillia fairfaxii (syn. Dendrobium teretifolium var. fairfaxii).
    • Sarcochilus parviflorus.
    • Sarcochilus dilatatus.
    • Sarcochilus weinthalii.

2b) Post-fire recovery in relation to Myrtle Rust impacts on Myrtaceae species

The SDZWA project has contributed towards the production of the high-quality video “Myrtle Rust, the Silent Killer” coordinated and produced by one of our collaborators and leading Myrtle Rust impact researcher in Queensland, Dr Geoff Pegg. This is a science-based plain-English video, targeted towards awareness-raising, particularly for land managers, policy influencers, bushcare workers and Indigenous communities, as well as wider audiences. Awareness-raising in these sectors remains a critical task, given the complexity of the issues and recovery strategies.

The video addresses a sample of species and ecological communities at risk from the pathogen, both burnt and unburnt in the 2019‒20 fires. However, the dual burn/pathogen interaction is a substantial focus. As quoted in the video “the combination of fire and Myrtle Rust has affected the regeneration of a range of plant species, killing seedlings and reshooting trees”.

‘Myrtle Rust, the Silent Killer’ can be viewed here.

Severely fire affected Myrtaceae species that are highly susceptible to Myrtle Rust, and covered by the video, include Rhodamnia rubescens, Gossia hillii, Archirhodomyrtus beckleri and Syzygium corynanthum, (wet/rainforest taxa seldom if ever previously burnt); Melaleuca quinquenervia (an irreplaceable keystone species of freshwater wetlands and floodplains), and Syncarpia hillii on K’gari [‘gah-ri’] formerly known as Fraser Island, a declared World Heritage Area, more than half of which burnt in 2020. The video has a major focus on a flagship program of post-fire Myrtle Rust monitoring on K’gari by the local Indigenous Ranger group, collaboratively developed by Dr Pegg, the Butchulla Aboriginal community and Queensland agencies. It is hoped that this example will enable a widening of Indigenous involvement in the Myrtle Rust response elsewhere in Australia.

The SDZWA project has been of great assistance in the Myrtle Rust response both directly in the case of the above video, and indirectly, e.g. by catalysing the production of the first exploratory paper (Zimmer et al., 2023) on the potential interactive effects on epiphytic orchids of Myrtle Rust infection of their host species, in the context of fire and Myrtaceae decline. It has also complemented the ANPC’s other Myrtle Rust projects following the 2019/2020 fires, such as the Safe Custody for Native Guava project.

Future work: Sampling and post-fire surveys of the impacts of Myrtle Rust will be undertaken on selected Myrtaceae species in 2025, to follow up on our Fire and Rust project from 2021.

References and further reading

Auld, T.D., Mackenzie, B.D.E., Le Breton, T., Keith, D.A., Ooi, M.K.J., Allen, S., Gallagher, R.V. (2020). A preliminary assessment of the impact of the 2019/2020 fires on NSW plants of national significance. NSW Department of Planning, Industry and Environment.

Auld, T.D., Keith, D.A., Gallagher, R.V., Tozer, M., Ooi, M.K.J., Le Breton, T., Allen, S., Yates, C., van Leeuwen, S., Williams, R.J. and Mackenzie, B.D.E. (2022). Frameworks for identifying priority plants and ecosystems most impacted by major fires. Australian Journal of Botany 70(7), 455–493.

Auld, T.D., Zylstra, P., Makinson, B., Coates, D. and Lynch, J. (2022). Assessing impacts and recovery after the 2019/2020 fires of priority plant species that were not previously threatened. Australasian Plant Conservation 31(2), 36-40.

Auld, T.D., Zylstra, P., Makinson, B., Coates, D. and Lynch, J. (2024). Preventing rare plant extinction and reducing impacts of future fires. Australasian Plant Conservation 33(1), 12-17.

Baird, I.R.C. and Benson, D. (2021). Population ecology of two endemic, fire-sensitive, Blue Mountains Banksia taxa (Proteaceae) in response to fire. Proceedings of the Linnean Society of New South Wales 143, 87-108.

Department of Agriculture, Water and the Environment (2022). Fire regimes that cause biodiversity decline as a key threatening process. Canberra, ACT.

Gallagher, R.V., Allen, S. and Auld, T.D. (2018). Identifying species at risk across current and future landscapes: Theme 3. Using range metrics to identify plants at risk. Report to NSW Office of Environment and Heritage from Macquarie University Bionode of NSW Adaptation Hub.

Gallagher, R.V. (2020). Final national prioritisation of Australian plants affected by the 2019-2020 bushfire season. Ver 1.4. Report to Commonwealth Wildlife and Threatened Species Bushfire Recovery Expert Panel.

Gallagher, R.V., Allen, S. Mackenzie, B.D.E., Yates, C.J., Gosper, C.R., Keith, D.A., … and Auld, T.D. (2021). High fire frequency and the impact of the 2019–2020 megafires on Australian plant diversity. Diversity and Distributions 27 (7), 1166-1179.

Gallagher, R.V., et al. and Auld, T.D. (2022). An integrated approach to assessing abiotic and biotic threats to post-fire plant species recovery: lessons from the 2019-20 Australian fire season. Global Ecology and Biogeography 31, 2056-2069.

Gallagher, R.V., et al. and Auld, T.D. (2023). Blackened roots and green shoots: emerging trends in decline and recovery in Australian plant species after the 2019–20 wildfires. In: Australia’s megafires: Biodiversity impacts and lessons learned from 2019-2020. Eds Van Leeuwen, S., Wintle, B.A., Woinarski, J.C.Z., Rumpff, L. and Legge, S.M. CSIRO Clayton South, Vic. Pp. 111-126.

IUCN Standards and Petitions Committee (2022). Guidelines for Using the IUCN Red List Categories and Criteria. Version 15. Prepared by the Standards and Petitions Committee.

Le Breton, T., Zimmer, H.C., Gallagher, R.V., Cox, M., Allen, S. and Auld, T.D. (2019). Using IUCN criteria to perform rapid assessments of at‑risk taxa. Biodiversity and Conservation 28, 863-883.

Le Breton, T., Ooi, M., Hay, S. and Auld, T. (2023). Conservation assessments from species assessments after the 2019-2020 fires. Australasian Plant Conservation 32(2), 3-6.

Lindenmayer, D.B., Bowd, E., Taylor, C. and Zylstra, P.J. (2023). Interacting and compounding impacts: fire and forestry in the 2019– 20 wildfires. In: Australia’s megafires: Biodiversity impacts and lessons learned from 2019-2020. Eds Van Leeuwen, S., Wintle, B.A., Woinarski, J.C.Z., Rumpff, L. and Legge, S.M. CSIRO Clayton South, Vic. pp 255–68

Makinson, R.O., Pegg, G.S. and Carnegie, A.J. (2020). Myrtle Rust in Australia – a National Action Plan. Australian Plant Biosecurity Science Foundation, Canberra, Australia.

Zimmer H, Clements M, Cooper E, Jones D, Makinson R, Nargar K, Stevenson K. (2023). Collateral damage: epiphytic orchids at risk from myrtle rust. Australian Journal of Botany, 71(8), 523–536.

Zylstra, P.J. (2021). Linking fire behaviour and its ecological effects to plant traits, using FRaME in R. Methods Ecol. Evol., 12, 1365–1378.

Zylstra, P.J., Bradshaw, S.D.A. and Lindenmayer, D.B. (2022). Self-thinning forest understoreys reduce wildfire risk, even in a warming climate. Environ. Res. Lett., 17, 044022.

Zylstra, P.J. (2022). Quantifying the direct fire threat to a critically endangered arboreal marsupial using biophysical, mechanistic modelling. Austral Ecology, 00, 1-23.

Zylstra, P.J., Wardell-Johnson, G.W., Falster, D.S., Howe, M., McQuoid, N. and Neville, S. (2023). Mechanisms by which growth and succession limit the impact of fire in a south-western Australian forested ecosystem Funct. Ecol. 37 1350–65.

Zylstra, P. (2023). Fires of the future. Wild 52–5

Zylstra, P. (2024). Reconciling fire behaviour science and forest ecology. Australasian Plant Conservation 32(3), 18-20.

Zylstra, P. J., Bradshaw, S. D. and Lindenmayer, D. B. (2024). Reply to comment on “Self-thinning forest understoreys reduce wildfire risk, even in a warming climate” Environ. Res. Lett. 19 058001.