Conservation Advice for the Drooping sheoak grassy woodland on calcrete of the Eyre Yorke Block Bioregion

Status: Critically Endangered on the EPBC Act list

This ecological community comprises the plants, animals and other organisms associated with a unique type of grassy woodland that is found in South Australia, east and south of Ceduna on the Eyre Peninsula and west and south of Port Clinton on the Yorke Peninsula.

Government evidence of impact of climate change:

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  • Conservation Advice for the Drooping sheoak grassy woodland on calcrete of the Eyre Yorke Block Bioregion

    The seasonal climate predisposes these regions to summer thunderstorms; high temperatures; low humidity and fires; with the latter historically resulting from lightning strikes during this season (DEH 2009a DEH 2010 Johnston Menz 2019).

    These include parasitic overload such as mistletoe and dodder laurel combined with insect attack; plant pathogens; changed salinity and nutrient levels and decreased soil moisture availability (partly due to climate change).

    Climate change Timing ongoing Climate change not only directly threatens species that cannot adapt it may also exacerbate existing threats; including loss of habitat; altered Severity hydrological regimes; altered fire regimes; knock down of shallow major unknown rooted trees during severe wind and storm events and invasive species.

    The potential large scale impacts of climate change could influence the Scope whole species composition of this ecological community through species responses to disturbance.

    Changes to climate are likely to impact upon the ecological community through seasonal shifts in temperature; evaporation and rainfall.

    Under severe climate change conditions average sequestration rates and carbon stocks are likely to be reduced by between 22 30 compared to historic conditions (Hobbs 2014).

    Atmospheric heat and about 40 of the total global ocean uptake of anthropogenic CO2 are absorbed by the Southern Ocean.

    The highly fragmented distribution of the Sheoak grassy woodland on calcrete makes it very susceptible to edge effects; the accumulative loss of patches and the collective action of fire; heavy grazing by stock and native herbivores; invasive species such as rabbits and over abundant native herbivores; senescence dieback; loss of native fauna; weeds and climate change.

    The canopy also affects microclimate through light transmission; temperature and humidity; and ameliorating damaging effects of wind and rain.

    Estimates of the effect of climate change on fire frequency and intensity indicate that the incidence of extreme bushfires may increase 25 by the year 2050 (Lucas et al. 2007 DEH 2009b).

    In addition; natural disturbances; such as changes in rainfall; temperature and seasonality; are likely to continue impacting the ecological community with storms likely to increase in severity and for longer periods due to climate change.

    They also change over time; for example; in response to disturbance (by logging; fire; or grazing); or to the climate and weather (e.g. seasons; floods; drought and extreme heat or cold).

    Be prepared Climate change and the South Australian bushfire threat.

    Additional grazing pressure from domestic and native herbivores on seedlings and vegetative suckers following fire has been noted to impact regeneration and can transform the structure of ecological communities e.g. to grassland or herbland (Auld et al. 2015 Auld et al. 2018).

    Loss of vegetation structure and composition can enhance the invasion and spread of exotic species; while high frequency fires and fire temperatures can increase mortality of fauna; slow or prevent regeneration of key flora species and lead to lower species richness.

    Loss of postfire habitat can lead to a subsequent increase in predation by feral or native predators on native fauna and increased weed spread.

    Weeds may alter fuel loads and lead to more frequent or more intense fires (Hobbs 2002).

    Increased temperatures and rainfall deficits reduce soil moisture and increases dried fuels; increasing bushfire potential.

    The South Australian EPA (2013) noted the South Australian Forest Fire Danger Index; one of the measures of bushfire threat; increased significantly for 42 of weather stations across South Australia.

    Once established weeds adversely affect native species through direct competition or by altering ecosystem processes; such as disrupting food webs or dispersal agents (as when natural pollinators visit weed rather than native species) or changing fire regimes (for instance the establishment of more flammable invasive grass species into a patch).

    Perennial veldgrass is tolerant of fire and can significantly increase fire fuel loads (QLD 2011).

    Where it has established on the edge or within patches of the ecological community; it can facilitate a change in the fire regime of a patch by promoting the spread of fires into the ecological community.

    They are contributing to a reduction in integrity of the ecological community and their impacts can be exacerbated by changes to fire regimes.

    Reduction in integrity through inappropriate fire regimes A further threat to the integrity of the ecological community is inappropriate fire regimes.

    While the pre 1750 fire regime is largely unknown; it is likely that the pattern and frequency of fire has changed considerably.

    It is likely that the frequency of naturally occurring fires has remained relatively stable but the disruption of burning by Indigenous people; change of land use and native vegetation structure has altered the size; interval; intensity and impact of bushfires (DEH 2009b).

    Fire history of other Drooping sheoak woodlands on Kangaroo Island before and after the 2019 20 bushfire season found that time since fire had a negative impact on cone quality.

    However; experience of fire impacts on the Eyre Peninsula indicates that 100 mortality rates in remnant patches can occur; particularly if seedlings and regenerating growth of mature trees are grazed; such as in the 1975 fires in the Sheringa district and the in 1997 fires near Coffin Bay (Bishop Venning 1986 Nosworthy Nosworthy 1988 Peeters et al. 2006).

    The general exclusion of fire from remnants also increases the likelihood that species which existed under a more frequent fire regime may be lost.

    Conclusion Substantial historical clearing and severe fragmentation; inappropriate fire regimes; senescence; invasive species; heavy grazing regimes; and other threats causing changes to flora and fauna diversity and vegetation structure have very severely reduced the integrity of the ecological community.

    The South Australian EPA (2013) noted the South Australian Forest Fire Danger Index; one of the measures of bushfire threat; increased significantly for 42 of weather stations across South Australia.

    As an example; in 2017; state fire agencies issued severe to extreme fire weather warnings and Forest Fire Danger Index values exceeded extreme levels for many sites.