Ecological consultants have reported on the impacts and changes that may be expected with a warming climate. Here is a summary of the information provided specifically for North Sydney Council.
The following article comes from:
North Sydney Natural Area Survey 2010 by P & J Smith (2MB)
"Anthropogenic climate change and its impacts are listed as key threatening processes in the Commonwealth"
Environment Protection & Biodiversity Conservation Act 1999, NSW Threatened Species Conservation Act 1995
While climate change has occurred throughout geological history, there is evidence that human-induced climate change is occurring at a faster rate than has previously occurred naturally. Furthermore, human-induced climate change is occurring in a highly modified landscape, which may limit the ability of organisms to survive climate change through dispersal (NSW Scientific Committee 2000). There is considerable evidence to suggest that the likely rate of climate change may be faster than the rate of natural adaptation. Substantial losses of biodiversity are thus likely (Howden et al. 2003).
Climate change is being caused by a build-up of carbon dioxide, methane and other 'greenhouse' gases in the earth's atmosphere. Atmospheric carbon dioxide and methane levels have risen rapidly and at an ever increasing rate over the last century (Bureau of Meteorology and CSIRO 2010). There is clear evidence that concentrations of greenhouse gases will continue to rise for a substantial period even if emissions are stabilised or decreased (Bureau of Meteorology 2003).
It is not possible to predict future climate trends with absolute certainty.
Models of climate change are being constantly refined as knowledge of the climate change process increases.
Current climatic modelling (Bureau of Meteorology 2003, CSIRO 2007, Bureau of Meteorology and CSIRO 2010) indicates that in coming decades in Eastern Australia, and hence North Sydney, average daily temperatures will rise, there will be more extreme hot days, and fewer cold days. Sea levels will rise as water temperatures rise, there will be increased storm and wave surges, and the shoreline will retreat inland. These may be exacerbated by changes in wind and wave direction. Decreases in rainfall are likely during Spring. An increase in the number of dry days is expected, but it is likely that there will be an increase in intense rainfall events, with associated increased flooding. The modelling predicts more frequent severe weather events. While the number of storm centres may decrease, their intensity is likely to increase. In the long-term, average evaporation and evapo-transpiration are likely to increase.
The projected rises in sea level would impact on low-lying vegetation communities such as the Estuarine Mangrove Forest, Estuarine Salt Marsh and Estuarine Swamp Oak Forest at the mouth of Berry Creek. The areas currently occupied by these communities are likely to become permanently inundated. Other vegetation communities fringing Port Jackson and Middle Harbour in North Sydney's various waterside reserves are likely to be reduced in area as their lower fringes become permanently inundated or intertidal. More frequent intense rainfall events would result in more frequent high flow events in creek lines such as Berry Creek, Quarry Creek and Willoughby Creek, with associated flooding, erosion, scouring of the stream bed, and movement of sediment. With most of North Sydney's remaining bushland occurring on moderate to steep slopes, the risk of increased erosion away from creek lines is also high.
Our understanding of how the natural environment will respond to climate change is limited. There are significant uncertainties in regard to biological responses to climate change, but the impacts on biodiversity are likely to be varied. Changes in the distribution and abundance of species are likely as marginal and sensitive species become more restricted or disappear, while other species better able to adapt increase. The distribution of weeds, pests and diseases will change. Increased carbon dioxide concentrations in the atmosphere may lead to changes in plant growth and nutrient composition in ecosystems. Species are likely to respond differentially to probable carbon dioxide fertilisation (Natural Resource Management Ministerial Council 2004).
In North Sydney, the structure and composition of the vegetation communities and faunal assemblages are likely to change as the competitive abilities of component species change. Weed and pest species which adapt readily to change may become more problematic. The capacity of bushland to recover from burning is likely to be decreased. As a result, the 'look and feel' of bushland areas may well change (Howden et al. 2003).
The long-term survival of individual species in the face of climate change will be determined by the rate and extent of change. For some species, survival will be determined by their ability to change their distribution, which will be dependent on their ability to disperse and the existence of suitable alternative habitats. Maintenance of species in-situ, and successful establishment of new populations and assemblages, will be constrained by the effects of land degradation and competition from invasive organisms (Natural Resource Management Ministerial Council 2004).
There is no doubt that the tasks of preserving biodiversity under climate change and facilitating adaptation will be more achievable and less costly if the magnitude of future climate change is reduced (Howden et al. 2003). While impacts of climate change may appear to be beyond the scope of local management, it is important to manage existing biodiversity to facilitate the long-term adaptation of species and communities to climate change. In North Sydney, climate change will exacerbate existing pressures on biodiversity. Current management should aim to build ecological resilience in bushland reserves by reducing existing impacts such as invasive weeds and altered fire regimens. Opportunities to rehabilitate or re-establish native vegetation on currently degraded land and to enhance habitat for already vulnerable species should be identified and implemented. The capacity of local flora and fauna to adapt to climate change is likely to be constrained by small populations, and hence low genetic diversity, coupled with isolation. Linkages between bushland remnants need to be enhanced wherever possible.
North Sydney Natural Area Survey 2010 by P & J Smith (2MB), Ecological Consultants