Climate change and Australia: Trends, projections and impacts

Abstract

This review summarizes recent research in Australia on: (i) climate and geophysical trends over the last few decades; (ii) projections for climate change in the 21st century; (iii) predicted impacts from modelling studies on particular ecosystems and native species; and (iv) ecological effects that have apparently occurred as a response to recent warming. Consistent with global trends, Australia has warmed ~ 0.8 Њ C over the last century with minimum temperatures warming faster than maxima. There have been significant regional trends in rainfall with the northern, eastern and southern parts of the continent receiving greater rainfall and the western region receiving less. Higher rainfall has been associated with an increase in the number of rain days and heavy rainfall events. Sea surface temperatures on the Great Barrier Reef have increased and are associated with an increase in the frequency and severity of coral bleaching and mortality. Sea level rises in Australia have been regionally variable, and considerably less than the global average. Snow cover and duration have declined significantly at some sites in the Snowy Mountains. CSIRO projections for future climatic changes indicate increases in annual average temperatures of 0.4-2.0 Њ C by 2030 (relative to 1990) and 1.0-6.0 Њ C by 2070. Considerable uncertainty remains as to future changes in rainfall, El Niño Southern Oscillation events and tropical cyclone activity. Overall increases in potential evaporation over much of the continent are predicted as well as continued reductions in the extent and duration of snow cover. Future changes in temperature and rainfall are predicted to have significant impacts on most vegetation types that have been modelled to date, although the interactive effect of continuing increases in atmospheric CO 2 has not been incorporated into most modelling studies. Elevated CO 2 will most likely mitigate some of the impacts of climate change by reducing water stress. Future impacts on particular ecosystems include increased forest growth, alterations in competitive regimes between C3 and C4 grasses, increasing encroachment of woody shrubs into arid and semiarid rangelands, continued incursion of mangrove communities into freshwater wetlands, increasing frequency of coral bleaching, and establishment of woody species at increasingly higher elevations in the alpine zone. Modelling of potential impacts on specific Australian taxa using bioclimatic analysis programs such as BIOCLIM consistently predicts contraction and/or fragmentation of species' current ranges. The bioclimates of some species of plants and vertebrates are predicted to disappear entirely with as little as 0.5-1.0 Њ C of warming. Australia lacks the long-term datasets and tradition of phenological monitoring that have allowed the detection of climate-change-related trends in the Northern Hemisphere. Long-term changes in Australian vegetation can be mostly attributed to alterations in fire regimes, clearing and grazing, but some trends, such as encroachment of rainfore...

Drought-driven change in wildlife distribution and numbers: a case study of koalas in south west Queensland

“…The ability of species to adapt to climate change will depend on several factors, including: (i) dispersal ability; (ii) phenotypic plasticity; (iii) evolutionary adaptability; and (iv) physiological tolerance (Williams et al 2008). Range shifts in response to higher temperatures have been seen in several species, generally either polewards or to higher elevations (Tidemann 1999;Hughes 2003;Thomas et al 2006;Thuiller et al 2008;Gibson et al 2009;Thomas 2010). Some species are showing signs of physiological adaptation to climate change, either through phenotypic plasticity or behavioural change (Parmesan 2006;Fuller et al 2010).…”

“…The drought and exceptionally hot years that occurred between 2001 and 2007 mimicked these climate change predictions. Climate change will also affect terrestrial vegetation and thus habitat quality and resource availability for many species (Hughes 2003). Changes in foliar chemistry due to elevated CO 2 are predicted to significantly affect arboreal folivores, including koalas (Kanowski 2001;Hughes 2003;Moore et al 2004;Lunney et al in press).…”

“…This fine scale structure leads to considerable variations in the density and numbers of local populations within the area of occupancy (Gaston and Fuller 2009). Changes in environmental conditions, such as climate variability and loss of habitat, affect population dynamics, including dispersal ability, breeding success and mortality rates, and alter population density either temporarily or permanently (Fahrig 2003;Hughes 2003;Parmesan 2006). These changes can occur cyclically, with populations expanding or contracting as environmental conditions fluctuate, but if conditions alter too much, there may be more permanent effects on populations (Thomas et al 2006;Piessens et al 2009).…”

“…Densities varied across the region from 0.0007 to 2.5 per ha, with the highest densities occurring in riverine and residual habitats in the eastern Mulgalands. Since that study was completed, south-west Queensland suffered a severe and prolonged drought (Hughes 2003;Beeton et al 2006) and anecdotal evidence suggested that regional koala numbers had declined.…”

Projected climate change in Australian marine and freshwater environments

“…Hughes 2003;CSIRO 2007;Hennessy et al 2007), it is likely that freshwater environments such as rivers and lakes are also being affected, although the evidence is less coherent (Lough and Hobday 2011). Changes in vegetation cover have exacerbated the effects of higher temperatures caused by climate change, resulting in longer-lasting and more severe droughts (e.g.…”