IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability

11.4.2 Natural ecosystems

The flora and fauna of Australia and New Zealand have a high degree of endemism (80 to 100% in many taxa). Many species are at risk from rapid climate change because they are restricted in geographical and climatic range. Most species are well-adapted to short-term climate variability, but not to longer-term shifts in mean climate and increased frequency or intensity of extreme events. Many reserved areas are small and isolated, particularly in the New Zealand lowlands and in the agricultural areas of Australia. Bioclimatic modelling studies generally project reductions and/or fragmentation of existing climatic ranges. Climate change will also interact with other stresses such as invasive species and habitat fragmentation. The most vulnerable include the Wet Tropics and Kakadu wetlands, alpine areas, tropical and deep-sea coral reefs, south-east Tasman Sea, isolated habitats in the New Zealand lowlands, coastal and freshwater wetlands and south-west Australian heathlands (Table 11.6). There is little research on the impacts of climate change on New Zealand species or natural ecosystems, with the exception of the alpine zone and some forested areas.

Table 11.6. Examples of projected impacts on species and ecosystems, relative to 1990.

Year Potential Impacts Source 
2020 Bleaching and damage to the Great Barrier Reef equivalent to that in 1998 and 2002 in up to 50% of years.  Berkelmans et al., 2004; Crimp et al., 2004 
 60% of the Great Barrier Reef regularly bleached. Jones, 2004b 
 Habitat lost for marine invertebrates currently confined to cool waters (>10% of Victoria’s total). O’Hara, 2002; Watters et al., 2003 
 63% decrease in golden bowerbird habitat in northern Australia. Hilbert et al., 2004 
 50% decrease in montane tropical rainforest area in northern Australia. Hilbert et al., 2001 
2030 58 to 81% of the Great Barrier Reef bleached every year. Jones, 2004b 
 Hard coral reef communities widely replaced by algal communities. Wooldridge et al., 2005 
 88% of Australian butterfly species’ core habitat decreases. Beaumont and Hughes, 2002 
 97% of Wet Tropics endemic vertebrates have reduced core habitat. Williams et al., 2003 
2050 97% of the Great Barrier Reef bleached every year. Jones, 2004b 
 92% of butterfly species’ core habitat decreases. Beaumont and Hughes, 2002 
 98% decrease in golden bowerbird habitat in northern Australia. Hilbert et al., 2004 
 80% loss of freshwater wetlands in Kakadu for a 30 cm sea-level rise. Hare, 2003 
2080 Catastrophic mortality of coral species annually. Jones, 2004b 
 95% decrease in distribution of Great Barrier Reef species. Jones et al., 2004 
 65% loss of Great Barrier Reef species in the Cairns region. Crimp et al., 2004 
 46% of Wet Tropics endemic vertebrates lose core habitat. Williams et al., 2003 
 200 to 300 indigenous New Zealand alpine plant species may become extinct. Halloy and Mark, 2003 
 Reduced calcification for 70% of the area where deep sea corals occur, loss of endemic species. Poloczanska et al., 2007 

Major changes are expected in all vegetation communities. In the Australian rangelands (75% of total continental land area), shifts in rainfall patterns are likely to favour establishment of woody vegetation and encroachment of unpalatable woody shrubs. Interactions between CO2, water supply, grazing practices and fire regimes are likely to be critical (Gifford and Howden, 2001; Hughes, 2003). In New Zealand, fragmented native forests of drier lowland areas (Northland, Waikato, Manawatu) and in the east (from East Cape to Southland) are likely to be most vulnerable to drying and changes in fire regimes (McGlone, 2001; MfE, 2001). In alpine zones of both countries, reductions in duration and depth of snow cover are likely to alter distributions of communities, for example favouring an expansion of woody vegetation into herbfields (Pickering et al., 2004). More fires are likely in alpine peatlands (Whinam et al., 2003). Alpine vertebrates dependent on snow cover for hibernation are likely to be at risk of extinction (Pickering et al., 2004). In regions such as south-western Australia, many narrow-ranged endemic species will be vulnerable to extinction with relatively small amounts of warming (Hughes, 2003). Saltwater intrusion as a result of sea-level rise, decreases in river flows and increased drought frequency, are very likely to alter species composition of freshwater habitats, with consequent impacts on estuarine and coastal fisheries (Bunn and Arthington, 2002; Hall and Burns, 2002; Herron et al., 2002; Schallenberg et al., 2003). In marine ecosystems, ocean acidification is likely to decrease productivity and diversity of plankton communities around Australia, while warmer oceans are likely to lead to further southward movement of fish and kelp communities (Poloczanska et al., 2007).

On the sub-Antarctic Islands, likely impacts include increased mortality of burrowing petrels, increased invasions by disturbance-tolerant alien plants such as Poa annua, increased abundance of existing rats, mice and rabbits on islands, and reduced distribution of Sphagnum moss (Bergstrom and Selkirk, 1999; Frenot et al., 2005).