Banksia Woodlands of the Swan Coastal Plain ecological community

Status: Endangered on the EPBC Act list

The Banksia Woodlands ecological community is a woodland located in the southwest of Western Australia, which is recognised as a global biodiversity hotspot. It is largely restricted to the Perth and Dandaragan subregions of the Swan Coastal Plain, from around Jurien Bay in the north to Dunsborough in the south. The ecological community also extends into immediately adjacent areas on the Whicher and Darling escarpments to the south and east, where pockets of Banksia Woodlands may also occur.

Government evidence of impact of climate change:

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  • Approved Conservation Advice (incorporating listing advice) for the Banksia Woodlands of the Swan Coastal Plain ecological community

    Climate change (increasing temperatures; declining rainfall; rainfall timing).

    There are ongoing threats to the ecological community; most notably from clearing for urban development; but also due to weed invasion; groundwater extraction; loss of fauna; dieback disease and potential impacts from climate change.

    In general; use locally collected seed where available to create an appropriate canopy and diverse understorey; however; choosing sources of seed closer to the margins of their range may increase resilience to climate change.

    Disturbances; particularly since European settlement; amplify this complexity major past disturbances (e.g. land clearing; logging; grazing) combine with ongoing threats associated with urbanisation (e.g. fragmentation; invasive species; arson; off road vehicles) and contemporary stressors (e.g. climate change) (Stevens et al.; 2016).

    Consequently there are fewer opportunities for colonisation due to rare long distance dispersal events; which are required to adapt to rapid climate change (Yates et al.; 2010).

    Climate change (increasing temperatures; declining rainfall; rainfall timing) Long term climate variability is affecting the southwest of Western Australia; which is experiencing a trend of increasing temperatures and declining rainfall.

    There is strong evidence that these changes are caused by anthropogenic climate warming; resulting in a southern shift of the Southern Annular Mode which brings rain bearing fronts from the Indian Ocean to the Western Australian coast (Steffen and Hughes; 2013).

    Groundwater decline is not only influenced by extraction but also by declining recharge rainfall rates as a result of climate change.

    Climate change may also result in temporal and spatial changes in hydrology within the Swan Coastal Plain.

    Changes in soil temperature and distribution of surface water as a result of a warming climate may have implications for Banksia species that are restricted to lower lying areas; such as B. ilicifolia (Groves; 2014).

    Climate change may reduce the number of seasonally waterlogged areas; as well as increasing the depth to groundwater; resulting in a decrease in the number of deep rooted species in these areas (Groom; 2004).

    A reduction in the integrity of the ecological community is evident from the effects of various threats including clearing and fragmentation; loss or decline of native flora and fauna; presence of invasive flora and fauna; hydrological degradation; altered fire regimes; dieback due to plant pathogens and climate change.

    Integrity is more likely to be affected in smaller and isolated remnants but can still apply to larger; less fragmented remnants of the ecological community as they remain subject to threats such as altered fire regimes; weeds; climate change and groundwater decline.

    They are vulnerable to disturbances that affect their key Banksia food resources; such as dieback; more frequent fires; groundwater changes and climate change.

    Climate change modelling predicts potential future declines in the abundance of honey possums of 20 to 50 ; depending on rainfall decline scenarios.

    Climatic drying also impacts on the success of seedling recruitment; which is highly sensitive to soil moisture levels (Enright and Lamont; 1992).

    Hence extensive mortality of Banksia Woodlands (Groom et al.; 2000) will rapidly become a more frequent phenomenon as the climate dries and the population of greater Perth increases.

    Further declines in ecological integrity of Banksia Woodland are resulting from an interaction between climatic warming; drying and increased bushfire risk (Enright et al.; 1998a;b; 2015).

    Consequently; a smaller proportion of the rare long distance dispersal events needed to keep pace with rapid climate change may result in colonisation (Yates et al.; 2010).

    Disturbances; particularly since European settlement; amplify this complexity major past disturbances (e.g. land clearing; logging; grazing) combine with ongoing threats associated with urbanisation (e.g. fragmentation; invasive species; arson; off road vehicles) and contemporary stressors (e.g. climate change) (Stevens et al.; 2016).

    Fire regime change (particularly increased fire frequency prescribed burning during late autumn to late spring when plants are in active growth; flowering and seed development and animals are active).

    Although fire is an important process in Banksia Woodlands; species such as B. prionotes; where adults are killed by fire but fire stimulates seeds to germinate; will be particularly vulnerable to high frequency or unseasonal fires.

    Certain fire regimes are inappropriate for the long term survival of the ecological community and these are a major threat to the diversity; viability and long term conservation of communities; habitats and populations of many species on the Swan Coastal Plain.

    These fire effects are the result of cool season prescribed burning; and high overall frequency of fires.

    This grass not only competes with native taxa; but it changes the fuel loads in bushland; resulting in bushland being more prone to arson and promoting higher fire frequencies (Stevens et al.; 2016).

    Such remnants are prone to impacts such as rubbish dumping (including garden waste as a source of weeds); access by unauthorised vehicles or paths created by people trampling through the vegetation; illegal removal of vegetation (including for firewood); increased patches of bare ground where vegetation cover has been destroyed; inappropriate fire regimes and introduction of domestic and feral animals (Stenhouse; 2004 DPaW; 2014 Ramalho et al.; 2014).

    Increased fire frequency creates feedback loops that promote the greater presence of weed species due to their shorter generation lengths; higher seedbanks and faster response to post fire ash bed nutrients than many native species (Fisher et al.; 2009 a; b).

    Reduction in integrity due to altered fire regimes Patterns of fire histories and regimes vary across the Swan Coastal Plain; but evidence shows that altered fire regimes are affecting the integrity of Banksia Woodlands at least in substantial areas; and in particular types of Banksia Woodlands (e.g. certain patch sizes).

    The responses of reptile species and assemblages to fire frequencies provide strong support for the maintenance of a range of post fire aged habitat and maintaining or increasing long unburnt Banksia Woodlands and other habitat types (Table E8 Valentine; 2012 Wilson et al.; 2014).

    Areas of remnant vegetation that are of small size and isolated from other remnants are particularly sensitive to the effects of altered fire regimes.

    Additionally; soils are being subject to calcium depletion in areas where the water table is undergoing rapid decline due to drought (Appleyard and Cook; 2009); a condition that is known to have caused widespread impacts on forest and woodland ecosystems in North America and Europe (Schaberg et al.; 2001 Schaberg et al.; 2010).