At a glance
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Source: Photograph courtesy of Sean McPhail
Links to content in detail
The detailed background report and supporting indicators are available through the following links:
At a glance – the issue
Warming of the global climate system is now unequivocal, with documented increases in the global average air and ocean temperatures, with melting of snow and sea ice, and rising average sea level (Internal linkIPCC 2007). There is very high confidence that regional climate change has occurred in Australia and New Zealand (Internal linkHennessy et al. 2007; Internal linkGarnaut 2008).
These global trends are evidenced in Tasmania with a 0.4–0.7°C temperature rise in the past century (Internal linkBarnes-Keoghan 2008), and a 10–20 cm sea level rise in the same period (Internal linkSharples 2006). Oceans are becoming warmer and more acid (Internal linkRaven et al. 2005; Internal linkAAD 2006). Climate-related threats to biodiversity when coupled with existing pressures have potential to have significant impact, particularly as global emissions are tracking at the upper limit of projections developed by the Intergovernmental Panel on Climate Change (Internal linkRaupach et al. 2007), a level of 'dangerous climate change'.
Some of the climate related changes that were anticipated or projected by scientists at Tasmania's first public Greenhouse Conference held in 1988 are now becoming evident in present observations, records and data. Collectively the changes point to an increasing climate change 'signal' in Tasmania as indicated by the responses of plants, animals and ecosystems. However, because there are often multiple causes or contributors to specific changes it is not possible to be definitive about the relative contribution of climate change to many of the changes. Examples of climate related changes to the environment in Tasmania include altered fire regimes, the drying of wetlands and reductions in streamflow, and the southward extension of the East Australia Current into southern Tasmanian waters.
Climate change and natural values: significance of pressure
The Australia and New Zealand report to the Fourth IPCC on Impacts, Adaptation and Vulnerability identified that some species and natural systems in Australia and New Zealand are already showing evidence of recent climate associated change (Internal linkHennessy et al. 2007). However, it identified that, in many cases, the relative contributions of other factors such as changes in fire regimes and land use are not well understood. This report also identified that there was very high confidence that significant loss of biodiversity is projected to occur by 2020 in some ecologically rich sites such as alpine areas.
The drivers of change may be direct on individual species and ecosystems through changes in vegetation composition, structure and function. They may also be indirect through the interactions between species, ecosystem level impacts, and through the threatening processes that impact biodiversity.
Tasmania's unique natural environments are already under a range of pressures including from invasive species and diseases, drought and loss or degradation of habitat. They are now facing additional challenges from climate change. Many plants and animals are found only in Tasmania, especially in our rainforests and alpine country where climate change is already having an impact. Coasts and oceans, and rivers and wetlands, are especially vulnerable to climate change. Wildfires are increasing in frequency and intensity and are a particular threat to Tasmania's world class reserve system and native forests.
The following graphical index is included as a visual method to allow a comparison of priority issues. Further information on the index is provided at Internal linkBackground to Index. The positioning of the dials for Climate Change and Natural Values reflect: (1) the increasing significance of impacts on natural values; (2) the spatial extent of the changes affecting both the terrestrial and marine environment; (3) and the relatively poor availability of information and knowledge about the potential effects on our native species and ecosystems because of the 'emerging' nature of the problem.
Natural values and climate change indexinternal SOE link to larger image
Conditions, trends and changes
- Key climate change consequences for natural values include higher fire frequency and severity, increased incidence of plant and animal diseases, increases in animal and insect populations, and pressure on ecosystems leading to the formation of new ecosystems and changes in ecosystem structure and function. Australian average temperatures have increased 0.9°C since 1950 (with significant regional variations). The frequency of hot days and nights has increased, the frequency of cold days and nights has declined, and the incidence of frosts reduced. The declining trend in cold days and cold nights has been observed in Tasmania and southeastern Australia generally (Internal linkCSIRO and the Bureau of Meteorology 2008).
- Information on fire frequency is provided in the indicator on Internal linkWildfire Frequency, Area and Cause. A key observed change in Tasmania is the increase in the number of high fire danger days, with an increase in the number of hot and dry windy days by 400% between 1996–2006. There has also been a significant increase in the number of fires caused by lightning strikes. In the decade to 2000, lightning strikes were responsible for 14 fires covering an area of about 11,000 ha. Research undertaken about 20 years ago showed no significant relationship between lightning and fire. However, since 2000, lightning strikes have been responsible for 55 fires in Tasmania affecting an area of about 60,000 ha (Internal linkDPIW 2008).
- Monitoring of the alpine zone is occurring at Mt Rufus and the Snowy Range in Tasmania, assessing the potential impacts on our flora. Studies are investigating the movement of eucalypt and shrub species into the alpine zone, and the impact on snowpatch communities. Indications are that recruitment and survival of seedlings is occurring into the alpine zone on Mt Rufus (Internal linkWhinam 2008).
- Changes in air temperatures and precipitation are having a range of detrimental effects on the ecology of inland waters and their associated fisheries in Tasmania. Changes in rainfall are amplified in runoff and streamflow; in wet and temperate catchments the percentage change in runoff is about twice the percentage change in rainfall (Internal linkChiew and McMahon 2002). Trends in streamflows are documented in the Internal linkStreamflow indicator. These trends are affecting the habitat of threatened native fish species such as the Internal linkSwan galaxias (Galaxias fontanus). The Swan galaxias is listed as Endangered under both the Threatened Species Protection Act 1995 and the Environment Protection and Biodiversity Conservation Act 1999. The 2000–01 summer was the driest on record in eastern Tasmania, and several monitoring river reaches were totally dry. Subsequent low rainfall years, including 2007 and 2008, have been even more severe for the Swan galaxias habitat. Similar issues arise for other native fish such as the Golden Galaxias (Galaxias auratus). There is concern that low lake levels could threaten the survival of this species, which is found only in Lake Sorrell and Lake Crescent.
- Changes in climate will alter the viability of pest and weed species that are currently outside of their preferred range. An example is Lantana, which is listed as a Weed of National Significance. There are credible reports of Lantana (Lantana camara) being sighted in gardens in the Hobart suburb of Sandy Bay. Should climate change provide this species with more favourable conditions, it potentially poses a very serious weed threat to the State (see also Internal linkPlant Pests (Weeds) and Native Plant Diseases).
- There is growing evidence that climate change will become one of the major drivers of species extinctions this century (Internal linkFoden et al. 2008) and is expected to result in changes in species' numbers, distribution and composition. However, determining the vulnerability of many species at risk is difficult to predict. Some species will be more vulnerable than others. For example, species with small or isolated ranges and low genetic variation will be more vulnerable. Remnant populations within reserves and ecosystems such as alpine zones and coastal wetlands are also likely to be particularly vulnerable (see also Internal linkWaterbird Population Trends Indicator).
- Susceptibility to climate change in birds shows strong taxonomic and geographic patterns, with all species within the albatross (Diomedeidae), penguin (Spheniscidae), petrel and shearwater (Proceccariidae, Pelecanoididae and Hydrobatidae) families considered at risk (Internal linkFoden et al. 2008). Climate change has been identified as a possible threat to Australian and Tasmanian seabirds, but little evidence of its direct effects are published, in part due to the paucity of long-term data sets. There are indications that the population of the Australasian Gannet in Bass Strait has increased and this may be attributable, in part, to climate change. The 2007 State of Australian Birds (Internal linkOlsen (ed) 2007) identified that the population of the Australasian Gannet experienced a three-fold increase over 22 years. This is thought to be associated with ENSO-related increases in sea-surface temperatures and higher pilchard abundance.
- The State of Australian Birds 2008 also reported on how some individual species are faring regionally based on a north-south transect that ran from the tip of Cape York to southernmost Tasmania (Internal linkOlsen 2008). The results showed that two of the reported species showed increases in their reporting rate in Tasmania. The Dusky Woodswallow showed decreases in the north of their range and increases in the south. The Scarlet Robin also showed decreases in the north of their range and increases in the south. Birds Australia has identified that these results could be interpreted as shifts in the distribution of the Scarlet Robin populations consistent with climate change (Internal linkOlsen 2008).
- An assessment of the impact of climate change on global amphibian species found that about half of them were susceptible to climate change, including Australian ground frogs (Limnodynastinae), tree frogs (Hylidae) and (Myobatrachidae) (Internal linkFoden et al. 2008). All of Tasmania's 11 species occur in these families.
- Whether particular species will out-compete as a result of climate change is not understood and, in general, there will be very low predictability about which species might disperse and establish rapidly in new areas and what impacts new species might have (Internal linkDunlop and Brown 2008).