The IllawarraÐShoalhaven subtropical rainforest ecological community occurs south of Sydney in NSW, in the Sydney Basin Bioregion. It occurs in the Illawarra, Jervis and Sydney Cataract IBRA subregions, and just over the borders into Burragorang, Moss Vale and Ettrema subregions.
Illawarra- Shoalhaven subtropical rainforest of the Sydney Basin Bioregion
Status: Critically Endangered on the EPBC Act list
Government evidence of impact of climate change:
-
Conservation Advice (incorporating listing advice) for Illawarra– Shoalhaven subtropical rainforest of the Sydney Basin Bioregion
They also change over time; for example; in response to disturbance (by clearing; fire; logging; or grazing); or to the climate and weather (e.g. floods; drought and extreme heat or cold).
Other increasing threats are from grazing and predation from feral and domestic animals and climate change.
Occurring in high or low light conditions; vines can smother both disturbed and undisturbed forest; reduce light levels and alter microclimate conditions of the understorey (ANPWS 1991).
Under future climate change scenarios for the region; it is likely that wetlands; moist open forest and rainforest will be under greater stress from fire and drought (NSW NPWS 2018) (also see Climate change; below).
Subtropical rainforests in the Shoalhaven region may be less likely to suffer serious impacts for climatic or microclimatic reasons; but this is not certain at this stage given more monitoring needs to occur (Makinson 2018).
Climate change General expected changes to biodiversity from climate change include (NSW DECC 2007) Species range shifts to cooler latitudes (south) or higher elevations Changes to flowering and fruiting times Behavioural changes in fauna populations Extinctions of local populations along range boundaries Increasing invasion of highly mobile; opportunistic; weedy plant species Progressive decoupling (breakage) of species interactions (e.g. timing of food availability) Increasing threat to fresh water ecosystems through changes in water temperature and chemistry and potential saline inundation Increased carbon dioxide will favour plants utilizing the C3 photosynthetic pathway of photosynthesis (rather than C4) this will alter competitive relationships between plants and may result in substantial changes in species composition; and increased competition from weedy species (Adam 2009) and Decoupling of pollinator plant relationships; leading to reduced pollination (Adam 2009).
Climate change predictions for the Illawarra and Shoalhaven regions indicate a shift to warmer minimum and maximum temperatures (more hot days and fewer cold nights) increased average fire weather in spring in the near future and increased severe fire weather in summer and spring over the longer term and; decreased rainfall in winter (and also spring for areas south of Gerringong and closer to the escarpment) and increased rainfall in summer and autumn (NSW OEH 2014).
These climatic changes mean that the structure and composition of the ecological community is likely to change.
Beyond these changes due to local climatic factors; changed disturbance regimes are also likely to cause further changes to patches of the ecological community.
The resilience of the ecological community is likely to be decreased under future climate change scenarios.
In addition; natural disturbances; such as fires and storms; are likely to continue impacting the ecological community and to increase in severity and or frequency due to climate change.
To get approval under national environment law; actions changes in land use in the buffer zone must not have a significant impact on the ecological community but there are exemptions for continuing use (e.g. existing cropping; grazing or maintaining fire breaks).
Other significant threats include further clearing (for urban and hobby farm developments; quarrying; road widening and utility easements) inappropriate fire regimes the cutting of trees for firewood and rubbish dumping (NSW Scientific Committee 2002a 2002b).
Remaining fragments tend to be degraded and continue to be threatened by weed invasion; pathogens; grazing; fire and urban expansion (Tozer et al. 2010).
However; because most rainforest species can regenerate after a single fire (Bowman 2000); it is the frequency of fires that is critical.
Weeds can substantially change fuel characteristics at rainforest boundaries (Bowman 2000).
Moreover; fragmentation exacerbates secondary processes; such as an altered physical environment (light; temperature; wind and storm damage); grazing and trampling; weed and feral animal invasion and increased fire risk (along with other threats associated with urban encroachment).
Decline in integrity due to altered fire regimes Repeated fires (increased frequencies) adjacent to patches of the ecological community are more likely to impact the ecological community; through drying and other changes to the ecological community and surrounding vegetation communities.
In the Hacking River valley; potential threats to native fauna of subtropical rainforest are recognised as habitat loss through high intensity fire events weed invasion; such as along some creeklines or adjacent to disturbed areas changes to water quality of some streams flowing through this habitat predation by feral predators grazing and trampling by the Rusa Deer road mortality potential infection of frogs by Amphibian Chytrid Fungus and feral fish populations; particularly the Mosquito Fish (NSW DECCW 2011c).
The impacts of some feral species often increases during drought and immediately after a fire; when food is scarce.
Impacts to forest canopy from extreme weather events may become more frequent; resulting in the accelerated loss of canopy individuals such as figs.
Decline in integrity due to altered fire regimes Repeated fires (increased frequencies) adjacent to patches of the ecological community are more likely to impact the ecological community; through drying and other changes to the ecological community and surrounding vegetation communities.