All recent state and territory SoE reports note the adverse effects of global climate change on biodiversity. These increasingly include extreme weather, as well as bushfire, drought, cyclones and flood. Climate change is predicted to generally exacerbate existing pressures; the general consensus is that the capacity of biodiversity to adapt to climate change will therefore be improved if other existing threats are addressed or ameliorated to some extent. Some state and territory reports also acknowledge that climate change could surpass habitat modification as the greatest threat to biodiversity in the next few decades. In an assessment of the pressures on New South Wales vegetation classes, climate change was the only pressure to affect all classes. It was described as the most pervasive pressure and described as ‘intensifying’ (NSW EPA 2012). Data about the impact of adverse climate as a pressure on animal distributions are generally not available, but individual species information suggests that this pressure is increasing, sometimes with devastating results. A Queensland Government report released in May 2016 reported the probable extinction of the Bramble Cay melomys (Melomys rubicola) from its only known island home in Torres Strait because of climate change (Gynther et al. 2016). The last known individual was sighted in 2009, and extensive surveys in 2014 failed to locate any animals. The key factor responsible for the extinction was the increased frequency and intensity of weather events, which produced extreme high water levels and damaging storm surges, and caused dramatic habitat loss and possibly direct mortality.
The broad impacts of climate change on biodiversity are increasingly well understood and are expected to vary, depending on the Australian region under consideration. In arid Australia, temperatures are predicted to increase, as are the frequency and intensity of extreme rainfall events, which are likely to increase threats to biodiversity directly and indirectly. In alpine Australia, changes in climate are already having significant impacts on biodiversity. In both Tasmania and Victoria, dynamic shifts in fire regimes are potentially leading to significant changes in ecosystems. In Tasmania, the 2015–16 summer was one of the driest on record.Lightning strikes ignited drying peat soils, causing large fires in remote areas. Some 124,742 hectares of country were affected by fires, including the globally unique fire-sensitive pencil pine ecosystems, with 20,125 hectares or 1.27 per cent of the Tasmanian Wilderness World Heritage Area burned. This was followed by the wettest 3-month period on record. Extreme heat events across Australia are the cause of high mortality for some fauna. For example, record temperatures in southern Queensland in January 2014 resulted in the (Welbergen et al.2014)
The Climate change adaptation plan for Australian birds (Garnett & Franklin 2014) assessed the vulnerability to climate change of all Australian bird species and subspecies that are resident on the continent or that visit on migration (1237 taxa in all) under a 2085 Representative Concentration Pathway (RCP) 8.5 scenario.1 The plan provided adaptation strategies for a 50-year timeframe for those taxa deemed most at risk. The risk model used was that vulnerability arises from a combination of sensitivity and exposure. A total of 177 birds were assessed as highly exposed, 151 as highly sensitive and 69 as both (referred to as highly vulnerable). Of the highly vulnerable species, 16 occupy the marine environment, and the remainder are terrestrial. A series of 12 management actions was developed and costed for each highly vulnerable species (or subspecies), giving an annual cost of adaptation of $5.08 million for just these birds.
Assessment of the extent to which species are vulnerable to climate change relative to other threats is necessary for effective recovery planning and conservation management. Lee et al. (2015) assessed the vulnerability to climate change of a sample of EPBC Act–listed species, including birds (44 species), mammals (43 species), amphibians (19 species) and reptiles (14 species) for which there were known population trends (recorded in 2002). Nearly half of these species were assessed to be vulnerable to climate change, with amphibians being the most vulnerable taxa. Species with smaller geographic ranges are more vulnerable than more widespread species.
Evidence is building that changes in phenology of Australian organisms are attributable to climate change. Phenology describes the timing of lifecycle events such as flowering and fruiting in plants, the onset of breeding in animals, the timing of migration, and the emergence date for arthropods. Shifts in phenology can affect ecosystems through changes in ecological interactions, such as plant–pollinator and predator–prey dynamics. These shifts have important consequences for agricultural production, human health, societies and economies. Shifts in phenology in Australian organisms have been documented in many long-term datasets, which show an average earlier phenology for plants of 9.7 days per decade (mostly based on data on grapevines from the viticulture industry) and for birds of 2.6 days per decade (Chambers et al. 2013). Examples of documented shifts in phenology include populations of dollarbirds (Eurystomus orientalis) and common koels (Eudynamys scolopacea) arriving significantly earlier at their south-eastern Australian breeding grounds (although not in more northerly regions).
Another pressure to coastal systems from global climate change is sea level rise, particularly for low-lying systems, such as coastal saltmarshes and terminal floodplain systems. Sea level rise may also carry a risk of irreversible damage to sacred and cultural sites, which can be (but is not always) significant for biodiversity. The pressure from sea level rise is described in more detail in the Coasts report.