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Published: 19 September 2011

Ecologists say logging increases risk of ‘mega’ fires

Logging in Victoria’s mountain ash forests is increasing the risk of catastrophic wildfires, according to a leading Australian ecologist.

When burned mature mountain ash forest becomes dominated by widespread areas of regrowth (which is more fire-prone), the risk of high-severity fire increases, and the probability of the landscape returning to its former mature state decreases.
Credit: Nick Pitsas/ScienceImage

In a study published in the US journal Proceedings of the National Academy of Sciences, a team led by Professor David Lindenmayer from the Australian National University analysed decades of ecological data, most recently from Victoria’s mountain ash forests after the 2009 Black Saturday bushfires.

The team concluded that timber and pulpwood harvesting carried out over large areas of Victoria’s mountain ash forests over the past century has created an area dominated by young fire-prone trees, increasing the risk of ‘mega fires’.

‘Before European settlement, the fire regime was dominated by an infrequent severe wildfire that occurred in late summer,’ says Prof. Lindenmayer.

‘What we are now realising is the combination of wildfire and logging is creating a previously unrecognised “landscape trap” in which the behaviour of the ash forest landscapes is markedly different from that which would have occurred before European settlement.

‘The core process underlying this landscape trap is a positive feedback loop between fire frequency and severity, and a reduction in forest age at the stand and landscape levels caused by logging.

‘Individual patches of logged forest are becoming more fire-prone, and when these are taken together, the whole landscape is at risk of being consumed by mega fires.’

Professor Lindenmayer adds that the increasing prevalence of dense young regenerating stands will lead to an increased risk of severe wildfires happening more often.

‘Detailed on-site measurements following the 2009 wildfires have revealed that young forest burns at higher severity than mature forest, and their analysis suggest we will see more of these severe wildfires in the future.

‘Once a mountain ash forest landscape is dominated by widespread areas of young fire-prone forest, the increased risk for high-severity widespread fire decreases the probability that the landscape can return to its former mature state – particularly under the drier and warmer conditions associated with climate change.

‘That’s why it’s described as a landscape trap; it’s self sustaining.’

The study also showed that, not only will these forests be more prone to extensive wildfire, but stands of mountain ash forest will be replaced by other species, particularly wattle.

‘These changes will significantly impair ecological functions like carbon storage, water production and biodiversity conservation,’ says Prof. Lindenmayer. ‘This is historically unprecedented and is beginning to dominate the mountain ash landscapes we see today.’

Source: ANU

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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