Category Archives: Fire

Fire blog 2: The significance of the 2019/20 SA bushfires

Throughout the decades the staff at the Botanic Gardens and State Herbarium have collected and curated plant specimens from all over the State. This enables the State Herbarium to document the native and introduced plant species that occur in South Australia.

The Herbarium’s collections contains more than one million plant specimens from all over the world; of these, more than 600,000 are South Australian plant specimens. In the early 2000s the State Herbarium of South Australia along with all other Australasian herbaria catalogued their Australian native plant collections and shared the data via a free online database, called the Australasian Virtual Herbarium.

This publicly available data based on the physical specimens in the herbarium collection allows current and future botanists to understand our flora in an ever growing way. Here, I have generated biodiversity assessments of the South Australian flora presented as maps of high diversity areas using all of the information in these collections.

By dividing South Australia into 10km grid cells, it is possible to calculate, which areas in the State contain the greatest number of plant species (richness), and which ones contain the greatest number of plants that are unique to South Australia (endemism). These maps show that both the Adelaide Hills and Kangaroo Island are two significant floral diversity areas for South Australia.

The maps present results that display one of the reasons why the fires that occurred in late 2019 and early 2020 may be a concern for the future of South Australia’s plant biodiversity. We can visually observe some of the reasons for concern by overlaying the locations of the past summer’s fires onto maps of South Australian plant species richness and South Australian plant endemism (see below, using data from NASA FIRMS).

Richness

The figure below is a map of South Australian plant species richness. The majority of areas that contains the most species (i.e. the areas in red) is higher mountain regions such as the Flinders Ranges and the Adelaide Hills, as well as the Eyre Peninsula, Kangaroo Island, and the south-east.

A species richness analysis of South Australian plants using plant records from all Australasian herbaria collected since 1802. Grid cells are 10 × 10 km2. Where the fires of 2019/2020 occurred are the brown dots. The inset box shows Kangaroo Island and the Adelaide Hills and the dots represent fire areas of December 2019 and early January 2020. It can be seen that many of the high plant diversity cells of the western and northern parts of Kangaroo Island have been severely impacted by the fires.

Zooming in on the fire areas of Kangaroo Island and the Adelaide Hills, it can be seen that the fire has occurred in areas that contain some of the highest number of plant species in the State. The Adelaide Hills fires have burnt across a smaller number of the map grid cells in comparison to the Kangaroo Island fire. The Adelaide Hills fires still occurred in areas of high plant diversity.

The Kangaroo Island fires burnt across the majority of species rich cells on the western half of the island, but it is also important to note that many of the species that grow on the western end of Kangaroo Island are very different to those that grow on the eastern side of the island (which was mainly unburnt).

To analyse this in more detail, the second measure becomes important, i.e. endemism.

Endemism

South Australia has three significant concentrations of plant endemism – Kangaroo Island, Adelaide Hills and south-eastern South Australia. As can be seen in the figure below, the map cells with significant endemism in the western region of Kangaroo Island have been impacted by the fires. Part of the significant Adelaide Hills endemism has been burnt in the fires. The endemism area in the South-East of the State has not been affected by fire so far.

An endemism richness analysis of South Australian plants using plant records from all Australasian herbaria collected since 1802. Grid cells are 10 × 10 km2. Where the fires of 2019/2020 occurred are the brown dots. The inset box shows Kangaroo Island and the Adelaide Hills. South Australia has three significant concentrations of plant endemism – Kangaroo Island, Adelaide Hills and South-eastern South Australia. As can be seen the significant endemism cells of western Kangaroo Island have been impacted by the fire. Part of the significant Adelaide Hills endemism has been burnt in the fires.

It will be important that during the remainder of this autumn, no more fires occur in areas of high diversity or endemism. In particular, fire in the south-eastern part of South Australia would be problematic for plants that are unique to South Australia, even though some of these plants occur in Victoria on the other side of the State border.

Recovery of native vegetation

There have been significant bushfires in the past, e.g. there was a major fire on Kangaroo Island in 2007 that burnt most of the western side of the island. The Ash Wednesday fires of 1983 in the Adelaide Hills was also a significant fire event. In those instances the vegetation recovered over time.

As the cooler and wetter weather in autumn and winter continues, plants will begin to recover and germinate. Many Australian natives are adapted to recovering from fire and the eucalypts will soon start sprouting leaves from their epicormic buds or lignotubers, while grass trees will send up new shoots. Some plants are advantaged by fire and there will be mushrooms, mosses, sundews, and orchids that will appear over the forest floor in numbers.

As for some of the rare and endemic species on Kangaroo Island, we won’t be able to say for certain until it is safe enough to re-enter the areas where they occur, and probably until next spring, when flowering begins and plants can properly be identified; or even a year or two after that.

We have plant lists for many parts of Kangaroo Island which have been collated over the years through the work of the Kangaroo Island community, students, State Herbarium staff, the S.A. Seed Conservation Centre and many volunteers. These lists and locations will assist with understanding the recovery processes of the fire affected areas over the coming years.

Remarkable Rocks on Kangaroo Island post-fire (10 Jan. 2020). Photo: DEW.

Written by Andrew Thornhill, State Herbarium of South Australia & The University of Adelaide.

Fire blog 1: Recovery after fire

Xanthorrhoea semiplana subsp. semiplana flowering in Cox Scrub Conservation Park after fire. Photo: D. Murfet, SA Seed Conservation Centre.

Fire has been part of the Australian environment for a long time. Parts of the country have burned very regularly (such as grasslands, heathlands, savannahs), while other areas experiences fire rarely (e.g. tall mountain ash forests in Victoria), or almost never (e.g. rainforests in the tropics or some alpine areas in Tasmania).

Most Australian plants are fire-adapted and have strategies to cope with fire. Some re-sprout after fire, with green shoots bursting from blackened stems; for others, fire stimulates flowering, while other species take advantage of bushfires to germinate.

Well known examples of plants that survive fires well are:

There are also some fungi and mosses that will respond quickly to fires. However, there are also species that take a long time to recover or never do. For example, mistletoes and other epiphtes will not re-sprout when the host tree burns and many cryptogams (lichens, fungi & mosses) will take decades to re-establish important soil crusts.

Should fires occur too frequent, regeneration is also hampered, as the soil seed bank will be depleted. The severity of fires also affects the ability of plants to recover.

Post-fire landscapes need time to recover, so we need to adopt a “wait and see” approach. Often one, two or even three growing seasons are necessary to be able to establish, which species have recovered from fire and which ones not. While there will be much regeneration in the burned areas, identification of seedlings and young plants is very difficult and often botanists need to wait for these to flower to be certain of their identity.

Removal of weeds and prevention of weed spread is also very important to help native vegetation to thrive after a fire. But again, weed identification can be very difficult if there are only small seedlings present. Often, it may be better to wait until potential weeds grow larger or even until they start flowering, so their identity can be confirmed. This will prevent the “weeding” of native seedlings, i.e. of exactly the plants that we want to come back (see also AMLR fact sheet on woody weeds and fire; 2.3mb PDF).

More information can be found on our list of fire-related publications and websites. Soon, we will also post further blog articles about the fire response of certain species and groups of plants.

Banksia ornata cone releasing seeds after fire. Photo: D.Murfett, SA Seed Conservation Centre.

Compiled by State Herbarium botanist Juergen Kellermann.

Bushfires in Australia

New epicormic shoots grow from burned eucalyptus trunks. Photo: AMLR.

The 2019-20 bushfire event has had a devastating effect in Australia, burning over 19.4 mio hectares of land (7.7mio in densely populated southern Australia).

In South Australia, the estimate is that nearly 300,000 hectares burnt (at the time of this blog). This includes around half of Kangaroo Island (more than 200,000 hectares) and more than 20,000 hectares in the Cudlee Creek Fire in the Adelaide Hills.

The Botanic Gardens and State Herbarium have received many enquiries asking how the burned and damaged vegetation will recover, if plants should be replanted or sown, or what people can do to help.

A message from the Botanic Gardens and State Herbarium Director Dr. Lucy Sutherland can be read here.

To provide more information to the public, we have decided to launch a series of blog posts about the effect of fire on the Australian environment, as well as a separate page on this blog (see also tab on the top of the blog), where links to existing web-resources and publications are posted. We will up-date this regularly.

The effects of the bushfires on Kangaroo Island. Graphic prepared at the end of Jan. 2020 by DEW.