In this chapter, climate change is considered to be a driver of change and climate itself is the pressure. Australia’s biodiversity has evolved in a climate of extremes in heat and cold, wetness and dryness (see Chapter 3: Atmosphere). However, when climate changes within the geographic range of any individual species, the species can have difficulty adapting, especially if it is prevented from moving with its preferred climate by, for example, lack of suitable habitat or the presence of other species that compete for resources. Climate change is recognised widely as a future pressure on biodiversity90—an issue discussed further in Section 6. Here we focus on evidence that changing climate has been a pressure for at least the past several decades (Tables 8.19 and 8.20).
All recent SoE reports from the states and territories discuss climate change as an emerging and/or present pressure on biodiversity (Table 8.20). Most focus on likely future effects of climate change, particularly a worsening of existing pressures. Two examples from the 2009 Victorian SoE report illustrate recent consequences of climatic extremes that might or might not be due to long-term climate change but that exemplify what is expected from climate change in coming decades.43 In east Gippsland in 2007, extensive soil loss occurred when severe winter flooding followed major wildfires, which had removed most of the vegetation that would usually absorb and slow the flow of water. Similarly, severe dust storms in western Victoria in 2008, which occurred despite the widespread adoption of improved land management practices, were an example of the effects of the prolonged dry period experienced over the past decade.
Populations of several species of birds (e.g. rainbow lorikeet and long-billed corella, both native, and the introduced common starling, common blackbird, common myna and spotted dove) have shifted from the north-east to south-east, suggesting a response to climate change and demonstrating the superior adaptability of such species.85
Given the extensive rainfall and floods in large parts of Australia in 2010–11, it might be expected that the next SoE reports will observe responses in biodiversity related to wetness rather than drought.
|Type of change||Examples of responses observed|
|Genetic constitution||Shifts in genetic composition of fruit flies|
|Geographic ranges||Migration of several bird species to higher altitudes or higher latitudes|
|Lifecycles||Earlier mating and longer pairing of the large skink Tiliqua rugosa|
|Populations||Reduced reproduction in wedge-tailed shearwaters on Great Barrier Reef islands associated with higher sea temperatures|
|Ecotonal boundaries (changes to the boundaries between ecosystems)||Expansion of rainforest at the expense of eucalypt savanna woodland and grassland in the Northern Territory, Queensland and New South Wales (other nonclimatic factors have likely contributed to the observed shift)|
|Ecosystems||Eight mass bleaching events since 1979 on the Great Barrier Reef triggered by unusually high sea surface temperatures|
|Disturbance regimes||Changing fire regimes in southern Australia, consistent with drier and hotter climate|
Source: Steffen et al.1
|ACT||Prolonged drought, combined with the 2003 bushfires, has had a major effect on ecological communities (which are showing signs of recovery) and especially bird species (some of which have decreased in numbers and some of which have increased due to drought)|
|NSW||Climate change is the most pervasive threat that continues to intensify with an increasing impact across all classes of native plants—alpine, coastal, rainforest, wetland and arid classes are the most sensitive
Periods of drought exacerbate incompatibilities between production and conservation objectives of land management; climate change is likely to exacerbate the impacts of other threats on flora and fauna.
|Qld||Drought is suggested as a contributor to declines in many regional ecosystems|
|SA||Several species of birds, frogs, reptiles and fish are reported as being affected by drought along the Murray River. Drought has had a major impact on native species (e.g. fish, birds) and habitat quality in the Coorong and Lower Lakes as well as the Murray River. Prolonged drought (from 2000) resulted in extensive lake acidification and extreme salinisation of the Coorong
Recent rains have provided some mitigation of these impacts but the recovery of crucial ecosystems remains uncertain91
|Tas||All frog species in the state are in families expected to be susceptible to climate change. Recent changes that appear to have affected frogs include changes in streamflows, loss of wetlands and shifts towards temperatures optimal for infectious diseases of frogs
Droughts draw many animal species towards roads and bias population estimates (upwards)
Evidence of changes in biodiversity due to climatic change include increased woodiness in the alpine zone that is likely to lead to greater fire risk; an advancing treeline (above the established treeline) at monitoring sites; and evidence of dieback related to drought or sustained high temperatures in conifers
Drought has caused locally severe dieback of trees and understorey species in eastern Tasmanian forests and on the Central Plateau, particularly on areas of shallow soil
|Vic||Six plant species are threatened by drought. Extended drought has decreased livestock populations (thereby alleviating grazing pressure), but increased the combined effects of water stress, fires and wind on loss of vegetation and soil|
|WA||Seedlings are vulnerable to climate stressors in combination with changed fire regimes|
|National||Changes in climate are at least partly implicated in real declines of 14 species listed as nationally threatened (8 birds, 1 reptile, 2 amphibians, 2 fish and 1 insect)
Evidence of changes related to climate warming over the past few decades is reported (reduced snow cover, ice melt in lakes, eucalypt recruitment above the alpine treeline, altitudinal expansion of the range of rabbits and the timing of arrival of migratory species)
ACT = Australian Capital Territory; NSW = New South Wales; NT = Northern Territory; Qld = Queensland; SA = South Australia; Tas = Tasmania; Vic = Victoria; WA = Western Australia