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Published: 12 September 2011

Climatic tolerances: an Australian story

Tim Low

How will Australia’s native species survive climate change? Observed distributions are the main source of information drawn upon to answer this question, but they need to be interpreted cautiously. In particular, we need to put aside assumptions based on northern hemisphere evidence.

While Cooatamundra wattle’s distribution is only 100 km wide, it has become weedy in Queensland, NSW, Victoria, Tasmania, SA and WA, showing that its distribution doesn’t reflect its climatic tolerance.
Credit: Tim Low

In modelling studies, a species’ climatic needs are inferred from its distribution. A bird found only on cool wet mountains, for example, is expected to need a cool wet climate in future.

But, ecologists know that distributions often fall short of indicating climatic limits. For example, rabbits, foxes and hares occupy much hotter and drier places in Australia than their native ranges would suggest. Australian garden plants sometimes escape into the wild in regions warmer than those they come from,1 and plants grown for experimental purposes often thrive at elevated temperatures.24 Fossil and genetic evidence implies that many Australian species did not change their distributions in direct proportion to Pleistocene climate change.57

Species distributions in very cold regions show the influence of climate more strongly than distributions nearer the equator;8, 9 the harsher the climate, the stronger the climatic influence. In Australia, with its generally mild to warm climate, there is evidence that some limits are set by competition, fire, substrate, physical barriers such as deserts, and failure to disperse far from past refuges.

For example, the tooth-billed bowerbird (Scenopoeetes dentirostris) – which is confined to high altitudes of the wet tropics – is widely expected to retreat upslope if its habitat becomes hotter. But a leading expert on bowerbirds, Clifford Frith, has suggested that the lower limits of its distribution may be set not by summer heat, but by competition from metallic starlings (Aplornis metallica). The starlings spend summer in the north Queensland lowlands, retreating to New Guinea in winter. Should climate change reduce their numbers, e.g. by reducing their food supplies in New Guinea, the bowerbird might not retreat in the way expected.

Botanists the world over worry about alpine plants: not so much because mountains will become too hot for them, but because trees will creep upwards beyond existing lower altitude distributions. Transplant experiments show that most alpine plants can live in hotter places than their distributions suggest; it is competition from trees that limits their lower ranges.10 Many plants might be saved if invading trees are removed. Climate change adaptation should, in this situation, become vegetation management: a matter of stopping climate ‘winners’ from replacing ‘losers’.

Climate models predict a poor future for the golden bowerbird (Amblyornis newtonianus), another bird of Australia’s tropical upland rainforests.11 However, one study found that bird abundance in upland rainforests reflects the severity of the dry season, which probably restricts food availability.12 Replanting mountain slopes with rainforest trees that bear fruit in the dry season could improve the bowerbird’s prospects under climate change. Adaptation would again be about managing plants: this time by adding them to the landscape.

Australia has thousands upon thousands of plants and animals with very small ranges. They could face serious risks from climate change; but in truth, we know too little about most species to rank the various threats they may face.

When assessing these species, we should not be governed by thinking generated in the northern hemisphere, where ecosystems are so different. Examples of animals and plants responding to climate change come mainly from cold regions of Europe and North America,13 and may prove uninformative for Australia.

We should consider what is distinctive about Australia, and factor that into our thinking. A drying, fire-prone landscape with infertile soils helps explain why we have so many species with small and climatically incoherent distributions, and how they might be managed. Better fire management is an obvious need, but climate change is also a reason to invest more in controlling flammable weeds, conserving pollinators, and researching fire, soil attributes and vegetation succession. We need a uniquely Australian perspective on climate change biology to help our adaptation toolkit grow.

Tim Low is a biologist and author who has written several reports about climate change and biodiversity, including a recent major report for the Queensland Government: Climate Change and Terrestrial Biodiversity in Queensland

1 Low T (2011). Climate Change and Terrestrial Biodiversity in Queensland, Brisbane: Department of Environment and Resource Management, Queensland Government.
2 Saxe H, Cannell MGR, Johnsen B, Ryan MG and Vourlitis G (2001). Tree and forest functioning in response to global warming. New Phytologist 149, 369–99.
3 Loehle C (1998). Height growth rate tradeoffs determine northern and southern range limits for trees. Journal of Biogeography 25, 735–42.
4 Ghannoum O, Phillips NG, Conroy JP, Smith RA, Attard RD, Woodfield R, Logan BA, Lewis JD and Tissue DT (2010). Exposure to preindustrial, current and future atmospheric CO2 and temperature differentially affects growth and photosynthesis in Eucalyptus. Global Change Biology 16, 303–19.
5 Markgraf V and McGlone M (2005). Southern temperate ecosystem responses. In Climate Change and Biodiversity. (Eds T Lovejoy and L Hannah) pp. 142–56. New Haven, Yale University.
6 Harrison SP and Goni MFS (2010).Global patterns of vegetation response to millennial-scale variability and rapid climate change during the last glacial period. Quaternary Science Reviews 29, 2957–80.
7 Byrne M (2009). Did Australian species stay or move when climate changed in the past? In Australia’s Biodiversity and Climate Change. (Eds W Steffen, AA Burbidge, L Hughes, R Kitching, D Lindenmayer, W Musgrave, M Stafford Smith and PA Werner) p. 93. Melbourne, CSIRO.
8 Araujo MB and Luoto M (2007). The importance of biotic interactions for modelling species distributions under climate change. Global Ecology and Biogeography 16, 743–53.
9 Woodward FI (1988). Temperature and the distribution of plant species. In Plants and Temperature. (Eds SP Long and FI Woodward) Cambridge, The Company of Biologists Limited.
10 Engler R et al. (2011). 21st century climate change threatens mountain flora unequally across Europe. Global Change Biology 17, 2330–41.
11 Hilbert DW, Bradford M, Parker T and Westcott DA (2004). Golden bowerbird (Prionodura newtonia) habitat in past, present and future climates: predicted extinction of a vertebrate in tropical highlands due to global warming. Biological Conservation 116, 367–77.
12 Williams SE and Middleton J (2008). Climatic seasonality, resource bottlenecks, and abundance of rainforest birds: implications for global climate change. Diversity and Distributions 14, 69–77.
13 Parmesan C (2006). Ecological and evolutionary responses to recent climate change. Annual Review of Ecology Evolution and Systematics 37, 637–69.

Published: 26 September 2011

Renewable energy sector to benefit from wind-speed research

Craig Macaulay

While some recent international studies have shown a decrease in wind speeds in several parts of the globe, including Australia, more recent results from CSIRO show that Australia’s average wind speed is actually increasing.

The ability to accurately quantify long-term variations in wind speeds is essential to the viability of Australia’s wind power sector.
The ability to accurately quantify long-term variations in wind speeds is essential to the viability of Australia’s wind power sector.
Credit: Gregory Heath

CSIRO scientists have analysed wind speed observations to understand the causes of variations in near-ground-level wind and explore long-term wind speed trends.

Accurate estimates of long-term trends provide a useful indicator for circulation changes in the atmosphere and are invaluable for the planning and financing of sectors such as wind energy, which need to map risk management under a changing climate.

‘We have a good picture of wind energy availability across Australia from previous CSIRO wind mapping and, with the growth of wind farms, there is an emerging need to understand how climate change can affect the wind resource,’ says Dr Alberto Troccoli, lead author of a recent paper published in Journal of Climate. 1

‘Wind power production is expected to increase greatly over the coming years and the associated electricity system will be subject to variations of several hundred megawatts – depending on wind availability.

‘The ability to quantify with accuracy these long-term variations is essential to the sector from an economic point of view.’

Dr Troccoli said that, averaged across Australia over 1989–2006, wind speeds measured at a height of 10 metres had increased by 0.69 per cent per annum, compared to a decline of 0.36 per cent per annum for wind speeds measured at 2m height.

‘The potential for increasing the efficiency of energy operations by using quality weather and climate information is therefore apparent and one of the first steps is the standardisation of wind recording stations.

‘Wind observations, like other meteorological variables, are sensitive to the conditions in which they are observed – for example, where the instrumentation sits relative to topographical features, vegetation and urban developments.’

The team found that the wind speed trends over Australia are sensitive to the height of the station, with winds measured at 10m displaying an opposite and positive trend to those reported by a previous study, which analysed only winds measured at 2m.

Light winds measured at 10m, a height that represents better the free atmospheric flow, tend to increase more rapidly than the average, whereas strong winds increase less rapidly than the average winds. Light and strong wind measured at a height of 2m tend to vary in line with the average winds.

‘Our work shows a number of challenges with the consistency of the observations during their period of operation and between sites across Australia,’ adds Dr Troccoli.

‘The quality of future wind observational datasets will depend on having consistency between sites, particularly with respect to measurement procedure, maintenance of instrumentation, and detailed records of the site history.’

He said the work has implications for a variety of sectors beyond wind energy including building construction, coastal erosion, and evaporation rates.

The conjunction of energy and meteorology is the central theme of the International Conference Energy & Meteorology on the Gold Coast in November.

Read Dr Troccoli’s thoughts on What’s the energy forecast? Bringing meteorology and generation together in the online forum, The Conversation.

1 A. Troccoli, K. Muller, P. Coppin, R. Davy, C. Russell and A. Hirsch (2011) Long-term wind speed trends over Australia. Journal of Climate, doi: 10.1175/2011JCLI4198.1

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